THE  MAKING,  SHAPING 

AND 

TREATING  OF  STEEL 


BY 
J.  M.  CAMP 

AND 

C.  B.  FRANCIS 


SECOND  EDITION 


PUBLISHED  BY 

THE  CARNEGIE  STEEL  COMPANY 

PITTSBURGH,  PA. 


Copyright  1920  by 

CARNEGIE  STEEL  COMPANY 

Pittsburgh,  Pa. 


TO 

HOMER  D.  WILLIAMS, 

President   of  the  Carnegie  Steel  Company 

AND 

HIS  ASSISTANTS 

For  Their  Valued  Suggestions  and  Words  of  Appreciation 
THIS  BOOK  IS  DEDICATED 


425274 


PREFACE  TO  SECOND  EDITION 

This  book  has  been  written  especially  for  the  nontechnical  employees 
of  the  Carnegie  Steel  Company,  and  others,  who,  seeking  self  instruction, 
may  desire  to  secure  in  the  shortest  time  possible  a  general  knowledge  of 
the  metallurgy  of  iron  and  steel. 

The  book  is  the  outcome  of  several  years  experience  in  attempting  to 
teach  the  metallurgy  of  steel  to  our  salesmen  and  other  nontechnical 
employees.  From  the  first,  the  method  pursued  in  this  work  has  been  that 
of  taking  the  students,  under  proper  guidance,  into  the  mills,  where  they 
obtain,  first  hand  and  individually,  such  information  as  they  desire  and 
are  able  to  collect,  and  of  supplementing  the  knowledge  gained  from  these 
visits  with  talks  and  explanations  delivered  in  a  classroom  where  conditions 
are  more  favorable  for  this  kind  01  instruction  than  they  are  in  the  mills. 
These  talks,  in  a  condensed  form,  were  put  in  writing,  and  a  copy  given 
to  each  of  the  students.  As  the  demand  for  these  lectures  increased,  it  was 
decided  that,  for  the  sake  of  convenience,  they  should  be  printed;  and 
accordingly  they  were  re  vised  and  are  here  assembled  in  the  present  volume. 

In  order  to  increase  the  value  of  the  book  as  a  reference  book,  we 
have  aimed  to  condense  the  information  and  to  avoid  every  unnecessary 
word,  both  by  omitting  all  matter  from  the  text  not  absolutely  essential 
and  by  the  free  use  of  tables,  drawings  and  diagrams,  which  we  permit  to 
tell  their  own  story.  However,  knowing  our  readers  will  be  men  imbued 
with  a  desire  to  learn,  we  have  not  avoided  discussing  many  scientific  aspects 
of  our  subjects.  But  here  we  have  tried  to  make  it  easy  even  for  the 
general  reader.  We  have  aimed  to  use  language  as  simple  as  possible, 
consistent  with  clearness,  and  to  treat  our  subjects  in  such  a  way  that, 
aside  from  what  a  limited  education  supplies,  no  prerequisites  will  be 
required.  We  start  with  the  elementary  subjects  of  Physics  and 
Chemistry,  the  logical  prerequisites,  and  build  our  metallurgy  upon  that 
foundation.  The  book  will,  therefore,  prove  of  most  value  to  those 
connected  with  the  steel  business,  and  not  technically  educated,  who  are 
really  anxious  to  learn  more  about  the  wonderful  industry  in  which  they 
are  engaged.  For  such  as  these,  we  have  aimed  to  make  this  book  at 
least  a  stepping  stone  to  higher  and  better  things. 


With  regard  to  the  subject  matter  of  the  book,  we  claim  but  little  in 
the  way  of  originality.  We  have  no  new  theories  to  advance  and  no  new 
discoveries  to  reveal.  Our  aim  throughout  has  been  to  describe  conditions 
and  things  as  they  are  and  to  explain  the  causes  for  their  being  as  they  are, 
rather  than  to  tell  how  they  might  be  or  how  they  ought  to  be.  To 
accomplish  our  first  purpose,  we  have  been  compelled  to  rely  mainly  upon 
our  personal  observation  and  experiences,  but  in  explaining  the  causes  of 
things  we  have  freely  consulted  all  those  whose  published  opinions  relating 
to  each  particular  subject  have  been  available  and  of  value.  We  are, 
therefore,  indebted  to  many  for  aid,  and  to  all  these  we  wish  to  express 
our  thanks.  Wherever  we  have  drawn  upon  these  sources  of  information 
we  have  aimed  to  give  the  credit  to  the  authors  by  mention  in  the  text 
or  by  foot  note  references.  As  guides  to  collateral  reading  these 
references  will  have  an  additional  value  to  our  readers.  We  also  desire  to 
thank  the  superintendents  and  the  many  heads  of  departments  of  our  various 
plants  for  the  courtesies  they  have  shown  us  and  for  the  many  bits  of  val- 
uable information  which  they  were  ever  ready  to  give. 


TABLE  OF  CONTENTS 

PART  I. 
MAKING  OF  STEEL 

CHAPTER  I     Some  Principles  of  Physics  and  Chemistry 

SECTION  I.       INTRODUCTION 

1.  Iron,  the  Master  Metal 1 

2.  Metallurgy  defined 2 

3.  Matter 2 

a.  Fundamental  Laws  and  States  of  Matter ....  2 

b.  Molecules 2 

c.  Sciences  of  Matter 3 

SECTION  II.         PHYSICAL  PROPERTIES  OF  MATTER. 

1.     Classes  of  Properties 3 

a.  General  Properties:  3 

i.     Inertia 3 

ii.     Extension 4 

iii.     Mass 4 

iv.     Density   and   Specific  Gravity 4 

v.     Porosity 4 

vi.     Impenetrability 4 

b.  Special  Properties 4 

i.     Cohesion  and  Adhesion 4 

ii.  Elasticity 4 

iii.  Plasticity 5 

iv.  Ductility 5 

v.  Malleability 5 

vi.  Hardness 5 

vii.  Crystallization 5 

viii.  Diffusion .  .  .  -. 5 

ix.  Effusion 5 

x.     Absorption ." 5 

SECTION  III.       ENERGY,  HEAT  AND  TEMPERATURE  AND  THE 
ETHER: 

1.  Energy — Law  of  Conservation 5 

a.    Kinds    of    Energy — Kinetic    and  Potential .  .  6 

2.  Heat  and  Temperature 6 

a.  Effects  of  Heat — Law  of    gas  expansion  and 

kinetic   theory 6 

b.  Temperature  Scales 6 

c.  Measurement  of  Heat 7 

3.  The  Ether..  7 


TABLE  OF  CONTENTS 


SECTION  IV.        CHANGES  IN  MATTER: 

1.  Physical  and  Chemical  Changes 8 

2.  Mechanical  Mixtures  and  Chemical  Compounds: 

a.  Solutions  and  Alloys 8 

b.  Acids,  bases,  salts,  and  non-electrolytes 8 

3.  The  Chemical  Elements 9 

a.  Classification  of  the  elements 9 

b.  Chemical  Symbols 9 

c.  Fundamental  Laws  of  Chemical  Changes. ...  9 
Definite    and    Multiple    Proportions 9 

SECTION  V.          THE  ATOMIC  AND  ELECTRON  THEORIES: 

1.  Atoms 10 

a.  Atomic  weights 10 

b.  Valence 10 

c.  Table  of  Elements  with  symbols,  etc 11 

2.  Electrons. 13 

SECTION  VI.        CHEMICAL  FORMULA  AND  REACTIONS: 

1.  Formula  of  Compounds 13 

2.  Formula  of  Molecules  of  Elements 13 

3.  Chemical  Equations 13 

a.  Balancing  reactions 14 

b.  Radicals 14 

4.  Ions  and  Electrolysis 14 

5.  Dry  and  Wet  Chemistry 15 

a.  Acids,  bases   and  "Salts  of   Dry  Chemistry . .  15 

b.  Table  of  anhydrides 16 

6.  Kinds  of  Reactions 16 

7.  Laws  of  Chemical  Reactions 17 

SECTION  VII.      CHEMICAL  NOMENCLATURE: 

1.  The  General  Principle  of  Nomenclature. . . 18 

2.  Terminology  of  Binary  Compounds 18 

3.  Terminology  of  Ternary  Compounds 18 

4.  Terminology  of  Acids 18 

5.  Terminology  of  Bases 19 

6.  Terminology  of  Salts ....... 19 

SECTION  VIII.    CHEMICAL  CALCULATIONS: 

1.  Kinds  of  Problems 19 

2.  Problems  involving  weight  only 19 

3.  Problems  involving  volume  only 20 

4.  Problems  involving  weight  and  volume 21 


TABLE  OF  CONTENTS  ix 

SECTION  IX.        DESCRIPTION    OF    ELEMENTS    IMPORTANT    IN 

IRON  AND  STEEL  MAKING: 
/^~* 

1.  Occurrence,    Preparation,      Properties    and      Some 

Compounds  of  Oxygen 22 

2.  Occurrence,    Preparation,    Properties     and      Some 

Compounds  of  Hydrogen 22 

3.  Occurrence,    Preparation,     Properties     and    Some 

Compounds  of  Sulphur 23 

4.  Occurrence,     Preparation,    Properties     and    Some 

Compounds  of  Carbon 23 

5.  Occurrence,     Preparation,      Properties   and    Some 

Compounds  of   Silicon 24 

6.  Occurrence,     Preparation,     Properties    and    Some 

Compounds  of  Nitrogen 25 

7.  Occurrence,     Preparation,    Properties     and    Some 

Compounds  of  Phosphorous 25 

8.  Occurrence,    Preparation,     Properties     and    Some 

Compounds    of    Calcium    and    Magnesium 25 

9.  Occurrence,     Preparation,     Properties    and    Some 

Compounds  of  Aluminum 26 

10.  Occurrence,     Preparation,     Properties    and    Some 

Compounds  of  Chromium 26 

11.  Occurrence,    Preparation,    Properties     and    Some 

Compounds  of  Manganese 27 

12.  Occurrence,    Preparation,     Properties    and    Some 

Compounds  of  Iron 27 

CHAPTER  II.    Refractories. 

SECTION  I.          NATURE  OF  REFRACTORIES: 

1.  Importance 28 

2.  Requirements  of  Refractories 28 

3.  Classes  of  Refractories 28 

SECTION  II.         ACID  REFRACTORIES: 

1.  Chemical  Composition 29 

2.  Silica  Bricks 29 

3.  Clay 29 

a.  The  Impurities  in  Clays 29 

b.  The  Process  of  Making  Fire  Clay  Brick. ...       30 


TABLE  OF  CONTENTS 


SECTION  III.       BASIC  REFRACTORIES: 

1.  Magnesia 30 

2.  Lime 30 

3.  Dolomite ...... 31 

4.  Bauxite 31 

SECTION  IV.        NEUTRAL  REFRACTORIES: 

1.  The  Ideal  Furnace  Lining .•?...  31 

2.  Graphite 31 

3.  Chromite 31 

4.  Protection  for  Refractories 31 

5.  Table — Chemical  Analyses  of     Refractories 32 

SECTION  V.          TESTING  REFRACTORIES: 

1.  Trial  Tests  and  Laboratory  Tests. .  33 

2.  Fusion  Temperature 33 

3.  Resistance  to  Compression 33 

4.  Expansion  and  Contraction 34 

5.  Slagging  Test 34 

6.  Density 34 

7.  The  Impact  Test 35 

8.  The  Abrasion  Test 35 

9.  Spalling  Test 35 


£H AFTER  HI.     Iron  Ores. 

SECTION  I.  ORES  AND  THE  IRON  BEARING  MINERALS: 

1.  Minerals  and  Ores 36 

2.  The  Iron  Bearing  Minerals 36 

a.  Magnetite  Group 37 

b.  Hematite  Group 37 

c.  Limonite  or  Brown  Ore  Group 37 

d.  The  Carbonate  Group 37 

3.  The  Mineralogical  Make-up  of  Iron  Ores 37 

SECTION  II.         VALUATION  OF  ORES: 

1.    Factors  in  the  Valuation  of  Ores 38 

a.  The   Impurities  that  Are  Never  Reduced  in 

the  Blast  Furnace 39 

b.  The      Impurities    that  May    Be     Partially 

Reduced 39 

c.  The  Impurities  Always  Reduced 40 

d.  Water ...  40 

e.  Accessibility 41 


TABLE  OF  CONTENTS 


SECTION  III.       THE  BIRMINGHAM  DISTRICT: 

1.  Location  and  General  Geology 42 

2.  Method  of  Mining 42 

SECTION  IV.        THE  LAKE  SUPERIOR  DISTRICT: 

1.     Importance,  Location  and  General  Geology 42 

a.  The  Marquette  Range 43 

b.  The  Menominee  Range 43 

c.  The  Gogebic  Range 43 

d.  The  Vermilion  Range 46 

c.     The  Missabe  Range 46 

f.     The  Cuyuna  Range 47 

SECTION  V.          MINING  THE  LAKE  ORES: 

1.  Prospecting  and  Exploration 47 

a.  Prospecting 47 

b.  Drjll  Exploration 47 

2.  Methods  of  Mining 50 

a.  Open  Pit  Mining 50 

i.    Siteamshovel  Mining 50 

ii.    Milling 52 

iji.    Scramming 53 

iv.     Advantages  of    Open  Pit  Mining 53 

b.  Underground  Mining — Slicing 53 

i.    Advantages  of   the  Slicing  System  of 

Mining 55 

ii.    Depth  of  Mine  Shafts 55 

3.  Grading  the  Ores 55 

4.  Transporting  the  Ores 56 

5.  Mining  and  Grading  in  Winter 57 

CHAPTER  IV.    Fuels. 

SECTION  I.  SOME  P RE-REQUISITES  TO  THE  STUDY  OF  FUELS: 

1.  Introductory •  58 

2.  Sensible  and  Specific  Heat 58 

3.  Latent  Heat  and  Change  of  State 59 

a.  Laws  of  Fusion 59 

b.  Laws  of  Evaporation 59 

c.  Laws  of  Ebullition 59 

4.  Transmission  of  Heat 59 

5.  Fuels  and  Combustion 60 

6.  Fuels  and  Chemical  Energy ; 60 

7.  Measurement  of  Calorific  Power t 60 

8.  The  Calorific  Power  of  Some  Common  Elements  .  61 

9.  Calculating  Calorific  Power , 61 

10.    Practical  Heat  Tests. .                       62 


Xll 


TABLE  OF  CONTENTS 


SECTION  I. — Continued. 

11.  Laboratory  Heat  Tests 62 

12.  Calorific  Intensity 63 

13.  Methods  of  Conserving  Heat 63 

14.  Pyrometers 64 

a.  Specific  Heat,  or  Water,  Pyrometer 64 

b.  Electric  Resistance  Pyrometers 64 

c.  Thermo-Electric  Pyrometers : 64 

d.  Radiation  Pyrometers 65 

e.  Optical  Pyrometers 65 

SECTION  II.         CLASSIFICATION  OF  FUELS: 

1.  Table— Classification  of  Fuels 66 

2.  Plan  of  Study 67 

SECTION  III.       INCIDENTAL  AND  LIQUID  FUELS: 

1.  Incidental  Fuels 67 

2.  Tar 67 

3.  Petroleum 68 

a.  Composition  of  Petroleum 68 

b.  Hydrocarbons — Generalized,   Empirical     and 

Structural  Formulas 68 

c.  Table — The  Different  Homologous   Series  of 

Hydrocarbons 69 

d.  Fuel  Oil  and  Other  Products  of  Petroleum.  69 

SECTION  IV.        GASEOUS  FUELS: 

1.  Advantages  of  Gaseous  Fuels 70 

2.  Table — Hydrocarbons  in  Natural  Gas  and  Petroleum  70 

3.  Natural  Gas 71 

4.  Artificial  Gases 71 

a.  Table — Composition   of   Gaseous  Fuels 71 

b.  Principle  of  the  Gas  Producer 71 

c .  Factors  Affecting  the  Efficiency  of  the  Producer  73 

d.  The    Hughes    Producer    as   an  Example  of 

Mechanically  Poked  Producer 73 

e.  Conditions  and  Reactions 74 

f.  Operation  of  the  Hughes  Producer 75 

SECTION  V.         THE  SOLID  NATURAL  FUELS: 

1.  Analysis  of  Solid  Natural  Fuels: 75 

a.    Table— Analysis  of    a  Solid  Fuel,  Coal,    by 

the  Three  Different  Methods 76 

2.  Wood 76 

3.  Peat , 77 

4.  Lignite  and  Brown  Coal 77 


TABLE  OF  CONTENTS  xiii 

SECTION  V.— Continued. 

5.  Table — Approximate    Analyses    of     the      Different 

Solid  Fuels 78 

6.  Diagram — Depicting    Geologic    Periods    in    which 

Gas,  Oil,  and  the  Valuable  Minerals  are  Found. .  79 

7.  Coal 80 

a.  Bituminous  Coal '. .  80 

b.  Ash  in  Coal 80 

SECTION  VI.        PREPARED  SOLID  FUELS: 

1.  Powdered  Coal 81 

a.  Requirements  for  Use  of  Powdered  Coal 81 

b.  Advantages  of  Powdered  Coal 82 

c.  The  Sharon  Powdered  Coal  Plant 82 

i.    Description  of  Pulverizing  Plant 82 

d.  Clairton  and  Homestead  Powdered  Coal  Plants  83 

2.  Coke 85 

a.     Methods  of  Manufacturing  Coke 85 

SECTION  VII.      THE  BEEHIVE  PROCESS  FOR  THE  MANUFACTURE 
OF  COKE: 

1.     The  Continental  No.   1  Plant  of  the  H.  C.  Frick 

Coke  Company 86 

a.  The  Mine 86 

b.  The  Coking  Plant 86 

i.    Construction  and  Arrangement  of  Ovens  86 

ii.    Waste  Heat  System 87 

iii.     Charging  the  Ovens 87 

iv.    The  Coking  Process 88 

v.    Watering  and  Drawing  the  Coke 89 

vi.     Longitudinal  Ovens 90 

SECTION  VIII.    THE     BY-PRODUCT  PROCESS   FOR    MANUFAC- 
TURING COKE: 

1.  General  Features  of  the  Process 90 

2.  Advantages  of  the  By-Product  Process 91 

3.  The     Plant    of     the    Clairton    By-Product    Coke 

Company 91 

a.  Construction  of  the  Ovens 93 

b.  Heating  the  Ovens 95 

c.  Drying  and  Heating  New  Ovens 96 

d.  Operation  of  the  Ovens 96 


xiv  TABLE  OF  CONTENTS 

SECTION  IX.        THE  BY-PRODUCT  PLANT: 

1.  The  Volatile  Matter  of  Coal 98 

2.  Gas  Mains  and  Coolers 98 

3.  Separation  of  the  Tar  and  Ammonia  Liquor ....  99 

4.  Compressors  and  Tar  Extractors 99 

5.  Recovery  of  Ammonia , . . .  100 

6.  Debenzolating  the  Gas 101 

SECTION  X.         THE  BENZOL  PLANT: 

1.  Light  Oil 101 

2.  Composition  of  Light  Oil 102 

3.  Construction  and  Principles  of  the  Still 102 

4.  Operation  of  the  Crude  Still 102 

5.  Washing  the   Products  of  the  Crude  Stills 103 

6.  The  Pure  Stills 103 

SECTION  XI.        SOME  PROPERTIES  AND  USES  OF  THE  RAW  BY- 
PRODUCTS FROM  THE  COKE  WORKS: 

1.  Characteristics  of  Benzol,  Toluol  and  Naphtha 105 

a.    Some  Members  of   the   Benzene   Series,  and 

their  Physical    Properties 106 

2.  Commercial  Benzol 107 

a.  Uses  of  Commercial  Benzol 107 

b.  Motor  Benzol. 107 

3.  Properties  and  Uses  of  Pure  Benzol,  or  Benzene.  . .  .  109 

a.  Table — Diagram     Showing     Some     of      the 

Products    Derived    from     Benzene,   Their 

Formulas  and  Their  Uses 108 

b.  Table — Reactions     Showing     How      Phenol, 

Picric    Acid     and      Resorcinol      may     be 

Derived  from  Benzene 110 

c.  Table — Reactions   Showing  How  Aniline  and 

Benzidine  are  Derived  from  Benzene 109 

4.  Usesof  Toluene Ill 

a.  Table — Some  Products  Derived  from  Toluene, 

Their  Formulas  and  Uses 112 

b.  Commercial  Toluol  and  Solvent  Naptha Ill 

5.  Uses  of  Naphthalene 113 

a.    Table — Showing     Some     Products     Derived 

from  Naphthalene 114 

6.  Tar 114 

a.     Diagram — Illustrative  of  the  Refining  of  Tar .  115 

7.  Ammonia 118 

a.  Ammonium  Sulphate 116 

b.  Use  of  Ammonium  Sulphate  as  a  Fertilizer. .  116 


TABLE  OF  CONTENTS 


CHAPTER  V.     Fluxes  and  Slags. 
SECTION  I.  FLUXES: 

1.  Smelting  and  the  Functions  of  a  Flux 117 

2.  The  Selection  of  the  Proper  Flux  for  a  Given  Process  117 

3.  Acid  Fluxes 118 

a.     Alumina 118 

4.  Basic  Fluxes 118 

a.  Available  Base 118 

b.  Limestone 119 

c.  Supply  of  Limestone 119 

d.  Action  of  Limestone  in  Furnaces 119 

5.  Neutral  Fluxes 120 

SECTION  II.         SLAGS: 

1.  Slag 120 

2.  Functions  of  Slags 120 

3.  Importance  of  Slags , 120 

4.  Chemical  Composition  of  Slags 121 

5.  Relation  of  Acids  to  Bases  in  Blast  Furnace  Slags. .  121 

6.  Ratio  of  Acids  to  Bases  in  Open  Hearth  Slags 122 

7.  Acid  to  Base  in  Acid  Furnaces 122 

8.  Electric  Steel  Furnace  Slags 122 

9.  Acids  Formed  by  Silicon . .  122 

10.  So-called  Acid  and  Basic  Slags 123 

11.  Classification  of  Slags.... 123 

12.  Uses  of  Slags 124 

CHAPTER  VI.    The  Manufacture  of  Pig  Iron. 

SECTION  I.          SOME  INTERESTING  HISTORICAL  FACTS: 

1.  Early  History  of  Iron 125 

2.  Old  American  Furnaces 126 

3.  The  Importance  of  Iron 126 

SECTION  It.         COMPOSITION  AND  CONSTITUTION  OF  PIG  IRON: 

1 1.     Constitution  of  Pig  Iron 126 

2.  Chemical  Elements  in  Pig  Iron 127 

a.  Carbon 127 

b.  Silicon 127 

c.  Manganese 128 

d.  Sulphur 128 

e.  Phosphorus 129 

3.  Grading  Pig  Iron 129 


TABLE  OF  CONTENTS 


SECTION  III.       A  BRIEF  OUTLINE  OF  THE  PROCESS  AND  EQUIP- 
MENT FOR  THE  MANUFACTURE  OF  PIG  IRON: 

1.  Trend  of  Modern  Improvements 130 

2.  Essentials  of  the  Process 130 

3.  Essential  Equipment 130 

SECTION  IV.        CONSTRUCTION  OF  THE  BLAST  FURNACE  PROPER: 

1.  The  Gross  Features  of  the  Furnace  Proper 131 

2.  The  Foundation 131 

3.  The  Hearth  or  Crucible 132 

4.  The  Bottom 132 

5.  Tapping  Hole 132 

6.  Cinder  Notches 134 

7.  Tuyeres 134 

8.  Tuyere  Connections 134 

9.  Boshes 135 

10.  Mantle 136 

11.  Shaft,  or  Stack,  and  In-Walls 136 

a.  Thick  Wall  Type 136 

i.    The  furnace  Lines  and  Bosh  Angles 136 

b.  Intermediate,  or  Semi-Thin,  Wall  Type 137 

c.  Thin  Walled  Type 137 

d.  Furnace  Linings 137 

12.  Water  Trough 139 

13.  Tops 139 

a.  Stock  Distributor 140 

b.  Hoisting  Appliances 140 

c.  Top  Openings 140 

d.  General  Consideration  for  Top  Construction. .  141 

14.  Runners 141 

SECTION  V.          BLAST  FURNACE  ACCESSORIES: 

1.  The  Stoves 142 

a.  Stove  Burners  and  Valves 143 

b.  Other  Stove  Openings 143 

c.  Stove  Linings 145 

2.  Dust  Catcher  and  Gas  Mains 146 

3.  Arrangement   of   Furnaces   and   Cleaning  Plant  at 

Duquesne 146 

a.  Primary  Division 148 

i.    Methods  of  Scrubbing  the  Gas 148 

ii.     The  Fans 149 

iii.    Water  Separator 149 

b.  The  Secondary  Division 149 

SECTION  VI.        EQUIPMENT  FOR  HANDLING  RAW  AND  FINISHED 

MATERIAL- 
1.     The   Boiler  House,  Power  Plant,  Pumping  Station, 

Blowing  Engines,  etc 150 


TABLE  OF  CONTENTS  xvii 


SECTION  VI.— Continued. 

2.  Dry  Blast 150 

3.  Cold  and  Hot  Blast  Mains 150 

4.  Appliances  for  Handling  Ores,  Coke  and  Stone 150 

5.  Stock  House  Equipment 151 

6.  Disposal  Equipment  for  the  Iron 152 

7.  Equipment  for  Slag  Disposal 152 

SECTION  VII.      OPERATING  THE  FURNACE: 

1.  Blowing  In 152 

2.  Drying 152 

3.  Filling 153 

4.  Lighting 153 

5.  Heating  the  Bottom 154 

6.  The  Heating  of  the  Stoves 154 

7.  Tapping 154 

8.  Care  of  Runners 155 

9.  Sampling  the  Iron 155 

10.  Tapping  Slag 156 

11.  Changing  Stoves 156 

12.  Charging  the  Furnace 156 

13.  Some  Irregularities  of  Furnace  Operation 157 

a.  Slips 157 

b.  Scaffolding 158 

c.  Chimneying  and  Hot  Spots 158 

d.  Loss  of  Tuyeres  and  Chilled  Hearth 158 

14.  Uncertainties  and  Variables  in  Furnace  Control 158 

15.  Banking 159 

16.  Blowing  Out. 159 

SECTION  VIII.    THE  BLAST  FURNACE  BURDEN: 

1 .  Burdening  the  Furnace 159 

a.  Outline  of  a  Method  for  Solving  a  Burdening 

Problem 161     ' 

b.  The  Burden  Sheet 161 

2.  Table  27.     Analysis  of  Raw  Materials  Used  in  the 

Blast  Furnace 160 

SECTION  IX.    CHEMISTRY  OF  THE  PROCESS: 

1.  Methods  of  Investigating  the  Reactions  of  the  Blast 

Furnace 163 

2.  The  Functions  of  Oxygen  and  Carbon 163 

3.  Behavior  of  Nitrogen  in  the  Furnace 165 

4.  Action  of  Phosphorus  in  the  Furnace 165 

5.  Disposition  of  Sulphur  in  the  Furnace 165 

6.  Behavior  of  Silicon 165 

7.  Action  of  Calcium  and  Magnesium . .  . .  : 166 

8.  Action  of  Aluminum. .  166 


TABLE  OF  CONTENTS 


SECTION  IX.— Continued. 

9.     Action  of  Less  Abundant  Elements 166 

10.  The  Reactions  Within  the  Furnace 167 

11.  Tracing  the  Materials  Through  the  Furnace 170 

12.  Conditions   Affecting  the  Amount  of    Silicon  and 

Sulphur  in  the  Metal 171 

CHAPTER  VII.    The  Bessemer  Process  of  Manufacturing  Steel. 

SECTION  I.  THE  CLASSIFICATION  OF  FERROUS  PRODUCTS: 

1.  Introductory 172 

2.  Pig  Iron  and  Cast  Iron , 172 

3.  Malleable  Cast  Iron 172 

4.  Wrought  Iron 173 

5.  Steel 173 

6.  Methods  of  Making  Steel 174 

7.  General  Principles  of    the  Methods  of     Purifying 

Pig  Iron 175 

SECTION  II.         PRINCIPLES  AND  HISTORY  OF  THE  BESSEMER 
PROCESS: 

1.  Principles  of  the  Process 175 

2.  Some  Incidents  Connected  with  the  Early  History 

of  the  Process ' 176 

3.  Importance  of  Manganese 176 

4.  Thomas  and  Gilchrist  Process 177 

5.  Other  Improvements 177 

6.  Plan  of  Study 177 

SECTION  III.       EQUIPMENT  AND  ARRANGEMENT  OF  THE  EDGAR 
THOMSON  PLANT: 

1.  The  Converter  House 177 

2.  The  Larger  Accessories 179 

a.  The  Cupolas 179 

b.  Charging  the  Cupola 180 

c.  The  Blast 180 

d.  The  Mixers, 181 

i.     Importance  of  the  Mixer 181 

e.  The  Stripper 181 

f.  The  Casting  Equipment 182 

i.    The  Ingot  Moulds 182 

SECTION  IV.        CONVERTER  CONSTRUCTION  AND  REPAIRS: 

1.  General  Features  Pertaining  to  Converters 183 

2.  Parts  of  Converter 183 

a.  Lining  of  the  Converter 184 

b.  The  Bottom 185 

i.     Relining  the  Bottom 185 


TABLE  OF  CONTENTS 


SECTION  V.          THE   CONVERTER  IN   OPERATION — PURIFYING 
THE  METAL: 

1.  Charging  the  Vessel 187 

2.  The  Blow 187 

3.  Controlling  the  Blow 188 

4.  The  End  of  the  Blow \ 189 

SECTION  VI.        FINISHING      OPERATIONS— CONVERTING     THE 

PURIFIED  METAL  INTO  STEEL: 

1.  Deoxidation  and  Recarburization 190 

2.  Loss  of  Recarburizer  and  Deoxidizer 191 

3.  Examples  of  Recarburizing 191 

4.  Ladle  Reaction 191 

5.  Teeming 192 

6.  Sampling  the  Steel  for  Chemical  Analyses 192 

SECTION  VII.      CHEMISTRY  OF  THE  PROCESS: 

1.  The  Order  of  Elimination  of  the  Elements 193 

2.  The  Laws  and  Conditions  Governing  the  Reactions 

in  the  Converter 193 

3.  Reactions  of  the  First  Period 194 

4.  Reactions  of  the  Second  Period 195 

5.  Chemistry  of  Recarburizing  and  Deoxidizing 196 

CHAPTER  VIII.    The  Basic  Open  Hearth  Process. 

SECTION  I.  SOME   GENERAL   FEATURES   OF  THE   SIEMENS 

PROCESS: 

1.  Early  History  of  the  Process 198 

2.  Principles  of  Siemens  Pig  and  Ore  Process 199 

3.  Advantages  of  the  Process 199 

4.  Mechanical  Changes  and  Improvements  in  Siemen's 

Process 200 

5.  Metallurgical  Improvements 200 

6.  The  Process  for  the  Pittsburgh  District 201 

SECTION  II.         EQUIPMENT    FOR    A    MODERN    BASIC    OPEN 

HEARTH  PLANT: 

1.  The  Modern  Plant 202 

2.  Calcining  Plant 202 

3.  Fuels 203 

4.  Fuel  Consumption 203 

5.  Hot  Metal  Mixer 204 

6.  Spiegel  Cupolas 204 

7.  The  Steel  Ladles 204 

8.  The  Stripper 205 

9.  Moulds 205 

10.  The  Charging  Machine 206 

11.  Charging  Boxes 207 

12.  Stock  Yard 207 

13.  Arrangement  of  the  Plant 207 


TABLE  OF  CONTENTS 


SECTION  III.        CHIEF    FEATURES    OF    BASIC    OPEN    HEARTH 
CONSTRUCTION: 

1.  Parts   of    the    Open    Hearth   Furnace    and    Their 

Arrangement 209 

2.  The  Furnace  Proper 209 

a.  The  Hearth 210 

b.  The  Walls 210 

c.  The  Roof 211 

d.  The  Bulk  Heads 211 

3.  The  Ports 211 

4.  The  Up-and-Down-Takes 211 

a.     Arrangement     of     Up-and-Down  Takes    for 
Natural    Gas,  Coke  Oven  Gas,  Powdered 

Coal  and  Tar 212 

5.  Slag  Pockets 212 

6.  Regenerators  for  Producer  Gas 212 

7.  Regenerators  for  Natural  and  Coke  Oven  Gases. . . .  216 

8.  Regenerators  for  Powdered  Coal 217 

9.  Flues  and  Valves 217 

10.     The  Stack 217 

SECTION  IV.        OPERATION    OF    A    BASIC    OPEN    HEARTH- 
PURIFYING  THE  METAL: 

1.  Furnace  Attendants  and  Their  Duties 218 

2.  Preparation. of  the  Furnace  for  its  First  Charge. . . .  218 

3.  Charging 219 

a.    The  Order  of  Charging  Raw  Materials 220 

4.  Melting  Down  the  Charge 220 

5.  The  Addition  of  the  Hot  Metal 221 

6.  The  Purification  Periods 221 

a.  The  Ore  Boil 222 

i.     The  Run  off 222 

b.  The  Lime  Boil 223 

c.  The  Working  Period.  ,...' 223 

i.     Methods     of   Working  the  Heat 223 

ii.     Testing  for  Carbon 224 

iii.     Control  of  Carbon  and  Temperature  . . .  224 

iv.    Judging  the  Temperature  of  the  Bath. . .  225 

7.  Tapping 225 

SECTION  V.          FINISHING  THE  HEAT— MAKING  STEEL  FROM 
THE  PURIFIED  METAL: 

1.  Methods  of  Finishing  the  Steel 226 

2.  Some  Features  that  Make  the  Finishing  of  the  Steel 

Difficult 227 

3.  Teeming 228 

4.  Sampling 229 


TABLE  OF  CONTENTS  xxi 

SECTION  VI.        KEEPING  THE  FURNACE  IN  REPAIR: 

1.  Preparation  of  the  Furnace  for  the  Next  Charge 229 

2.  Furnace  Troubles 230 

3.  Repair  Materials 231 

a.  Dolomite 231 

b.  Magnesite 231 

c.  Chrome  Ore 231     . 

SECTION  VII.      CHEMISTRY  OF  THE  BASIC  PROCESS: 

1.  Some  of  the  Principles  and  Conditions  Involved.,.  232 

2.  Properties  of  Iron  and  Its  Oxides 232 

a.     The  Importance  of  Ferrous  Oxide,  FeO,  in  the 
Part  Played  by  the  Oxides  of  Iron  in  the 

Process 233 

3.  Properties   of  Silicon  and   Its  Oxide,  Silica 234 

4.  Properties  of  Manganese  and  Its  Oxides 235 

5.  Sulphur  and  Its  Oxides 236 

a.     Sulphur  from  the  Fuel 237 

6.  Phosphorus  and  Its  Oxides 237 

7.  Carbon  and  Its  Oxides 238 

a.  The  Action  of  the  Limestone 239 

b.  Effect      of     Carbon     Elimination      on    Slag 

Composition 239 

8.  The  Order  of  Elimination 239 

a.     Factors  Opposing  this  Order  of  Elimination  240 

9.  Resume 241 

CHAPTER  IX.    Manufacture  of  Steel  in  Electric  Furnaces. 

SECTION  I.  INTRODUCTORY: 

1.  The  Plan  of  Study 243 

2.  Force,  Work,  Energy  and  Potential 243 

3.  Power 240 

4.  Transmission  of  Energy 244 

5.  Electromotive  Force  (E.  M.  F.) 246 

SECTION  II.         THE  DEVELOPMENT  OP  ELECTROMOTIVE  FORCES 

— OR  "GENERATION  OF  CURRENT:" 

1.  Methods  for  Setting  Up  Electric  Currents 246 

2.  Magnetism , 246 

a.  Magnets  and  Magnetic  Substances 247 

b.  Magnetic  Fields  and  Electric  Currents 248 

3.  Electromagnetic  Induction 249 

a.  Laws     of     Electromagnetic     Induction 250 

b.  The  Dynamo 250 

SECTION  III.       KINDS  OF  CURRENT: 

1.     Alternating  Current 251 

a.     Graphic  Representation  of  Alternating  Current  252 


TABLE  OF  CONTENTS 


SECTION  III.— Continued. 

2.  Direct  Currents 253 

3.  Polyphase  Currents 253 

4.  The  Two  Schemes  of  Wiring  for  Three  Phase  Current  254 

SECTION  IV.        TRANSMISSION  OF  THE  CURRENT: 

1.  Ohm's  Law 256 

2.  Resistance  of  Conductors 256 

a.  Effect  of  Temperature   on   Conductors 257 

b.  Resistance  in  Series  and  Parallel 258 

c.  Currents  Through  Divided   Circuits 259 

3.  *  Self-induction,  Impedance,  Power  Factor 259 

4.  Heat  Developed  in  Conductors 259 

5.  The  Stationary  Transformer, 260 

a.     Kinds  of  Stationary  Transformers 260 

SECTION  V.  THE  UTILIZATION  OF  THE  CURRENT  IN  ELECTRIC 
FURNACES: 

1.  Effects  Produced  by  Electric    Current 261 

a.  Chemical  Action  Produced  by  the    Electric 

Current 261 

i.     Electrical  Units  of  Measurements 262 

b.  The   Magnetic    Influence    of   the   Current 262 

2.  Heating  the  Bath 262 

a.  Heating  by  Direct  Resistance 263 

b.  Indirect  Resistance  Heating 264 

c.  Arc  Heating 264 

d.  Methods  of  Applying  the  Arc  in  Arc  Furnaces.  265 

i.     The  Stassano  Furnace 265 

ii.     Girod  Furnaces 266 

iii.     The  Principle  of  the  Heroult  Furnace ..  266 

3.  Some  General  Conclusions 267 

SECTION  VI.  GENERAL  FEATURES  PERTAINING  TO  THE 
METALLURGY  OF  STEEL  MADE  BY  ELECTRO- 
THERMAL PROCESSES: 

1.  Advantages  of  Electric  Heating. 267 

2.  Refining  Procedure 267 

a.  The  Oxidizing  Period 268 

b.  The  Reducing  Period ' 269 

i.     Oxygen 269 

ii.     Removal  of  Sulphur 269 

c.  The  Finishing  Period 270 

3.  Some  Comparisons 271 

4.  Fluxing  Materials 271 

5.  General  Manufacturing  Practice 271 


TABLE  OF  CONTENTS 


SECTION  VII.      THE  DUQUESNE  PLANT— FEATURES  PERTAIN- 
ING TO  ITS  CONSTRUCTION: 

1 .  Equipment 275 

2.  Construction  of  the  Furnace  Shell 275 

3.  The  Furnace  Lining 275 

4.  The  Roof 277 

5.  Controlling  the  Electrodes 277 

a.    The  Electrode  Holders 277 

6.  The  Electrodes 279 

7.  Furnace  Openings 279 

SECTION  VIII.    OPERATION  OF  THE  FURNACE: 

1.     Practice  at  Duquesne  Plant 279 

a.  Charging 280 

b.  Deoxidizing 280 

c.  Finishing  the  Heats 281 

d.  Tapping  and  Teeming 281 

e.  Scrap  Heats 281 

SECTION  IX.        THE  CHEMISTRY  OF  THE  PROCESS: 

1.  Deoxidation  of  the  Bath 286 

2.  Desulphurizing  the  Metal 286 

3.  Difficult  Specifications 288 

SECTION  X.         PROPERTIES  AND  USES  OF  ELECTRIC  STEEL: 

1.  Properties  of  Electric  Steel 289 

2.  Illinois  Steel  Company's  Tests  on  Rails 290 

3.  Uses  of  Electric  Steel 291 

4.  Summary 291 

CHAPTER  X.    The  Duplex  and  Triplex  Processes. 

SECTION  I.  GENERAL  FEATURES  OF  THE  DUPLEX  PROCESS: 

1.  What  the  Duplex  Process  Is 293 

2.  Advantages  and  Disadvantages  of  the  Process ....  293 

3.  Methods  of  Duplexing 294 

4.  The  Talbot  Furnace 294 

SECTION  II.         OPERATION  OF  THE  PROCESS: 

1.  An  Example  of  the  Duplexing  Process 295 

2.  Preparing  the  Furnace  for  Charging 295 

3.  Charging   Molten  Metal  from   the   Converters  for 

the  First  Heat 295 

4.  Tapping  and  Recarburizing  the  First  Heat 296 

5.  Preparing  the  Furnace  for  the  Second  Heat 296 

6.  Closing  Down  the  Furnace  for  the  Week  End 297 

7.  Slag 297 

SECTION  III.       COMBINATION  PROCESSES  IN  THE  SOUTH: 

1.  The  Duplex  Process  in  the  South 297 

2.  The  Southern  Triplexing  Process 298 


TABLE  OF  CONTENTS 


PART   II. 
THE  SHAPING  OF  STEEL 

CHAPTER  I.     The  Mechanical  Properties  of  Steel. 

SECTION  I.        GENERAL  REMARKS  PERTAINING  TO  THE  TESTING 
OF  STEEL: 

1.  The  Factors  that  Affect  the  Mechanical   Properties 

of  Steel 299 

2.  The  Two  Objects  in  the  Testing  of  Steel 299 

3.  Relative  Importance  of  Physical  and  Chemical  Testing  300 

4.  Nature  of  Physical  Testing 300 

SECTION  II.      THE  TESTING  OF  STRUCTURAL  AND  OTHER  SOFT 
STEELS: 

1.  The  Pulling  Test 301 

a.  Procuring  the  Test  Pieces 301 

b.  Preparation  of  the  Test  Piece 302 

c.  Pulling  the  Test 303 

i.     Graphic  Representation  of  Tests 304 

ii.     Reasons   for   the    Points   of    Yield    and 

Maximum  Stress 304 

d.  Examination  of  Test  After  Pulling 305 

e.  Calculating  the  Results  of  the  Test 306 

2.  The  Modulus  of  Elasticity,  or  Young's  Modulus ...  307 

3.  Relative  Importance  of  the  Mechanical  Properties  as 

Determined  by  the  Pulling  Test 307 

4.  Bending  Tests. 308 

SECTION  III.     THE    TESTING   OF   THE    HIGHER    CARBON    AND 
HEAT  TREATED  STEELS: 

1.  Kinds  of  Tests  Applied  to  the  Higher  Carbon  and 

Heat-treated  Steels 308 

2.  The  Tensile  Test • 308 

3.  The  Impact  Test 309 

4.  Hardness  Tests ....  309 

a.  Shore  Scleroscope 310 

b.  Brinell  Hardness 310 

i.     Relation  of  Brinell    Number    to  Tensile 

Strength 311 

CHAPTER  II.    The  Mechanical  Treatment  of  Steel. 

SECTION  I.        METHODS     AND     EFFECTS     OF     MECHANICALLY 
WORKING  STEEL: 

1.  Methods  of  Shaping  Steel 312 

2.  Benefits  of  Mechanical  Working 312 

3.  Hot  and  Cold  Working 313 


TABLE  OF  CONTENTS 


SECTION  II. 


SUMMARY  OF  THE  HISTORY  AND  PRINCIPLES  OF 
WORKING  STEEL: 


1.     The  Three  Methods  for  Mechanically  Working  Steel.  316 

a.  Hammer  Forging 316 

i.     Principles  and  Effects  of  Hammering ....  317 

b.  The  Forging  Press 317 

i.     The  Effect  of  Pressing 317 

ii.    Advantages  of  the  Press '.  318 

c.  Rolling 318 

i.     Principle  and  Effect  of  Rolling 319 

ii.     Rolling  Compared  with  Hammering  and 

Pressing 320 

iii.     Rolling  and  Pressing  Ingots 321 

CHAPTER  III.     Essentials  of  Rolling  Mill  Construction  and 

Operation. 

SECTION  I.        THE  ROLLS — THEIR  PREPARATION  AND  ARRANGE- 
MENT: 

1.  Parts   and     Equipment  of    the   Simplest    Type    of 

Rolling  Mill 322 

2.  The  Rolls  and  Their  Parts 322 

a.  The  Manufacture  of  Rolls 323 

b.  The  Sand  Roll 323 

i.    The  Materials  Used  in  Sand  Cast  Rolls..  324 

c.  Chilled  Rolls 324 

i.     Difficulties  in  Making  Chilled  Rolls 326 

d.  Steel  Rolls 326 

e.  Other  Rolls 327 

f.  The  Size  of  Rolls 327 

g.  Roll  Design 327 

i.    Methods  of  Procedure  in  Designing  Rolls  328 

ii.        Difficulties  in  Designing  Rolls 328 

h.    Turning  the  Rolls 329 

i.     Dressing  the  Rolls 329 

3.  Types  of  Mills 330 

SECTION  II.      PARTS  OF  THE  MILL  ESSENTIAL  TO  THE  OPER- 
ATION OF  THE  ROLLS: 

1.  The  Chocks 331 

a.  The  Arrangement  of  the  Chocks 331 

b.  The  Function  of  the  Chocks 332 

2.  The  Housings 332 

a.    The  Adjusting  Equipment 333 


TABLE  OF  CONTENTS 


SECTION  II.- Continued. 

3.  The  Pinions v 333 

4.  The  Connections . 334 

5.  Guides  and  Guards 334 

6.  Additional  Equipment 335 

SECTION  III.     SOME     GENERAL     FEATURES     PERTAINING     TO 
OPERATION  OF  THE  ROLLING  MILL: 

1.  The  Mill  Force 336 

a.     Duties  of  the  Roller 336 

2.  Fins 336 

3.  The  Different  Passes  and  Stands 337 

4.  Factors  Affecting  the  Rolling  Operation 337 

5.  Effects  of  Temperature 337 

6.  Effect  of  Chemical  Composition 338 

7.  The  Effect  of  Speed 339 

8.  Draught 339 

9.  The  Effect  of  Diameter  of  Rolls 340 

CHAPTER  IV.    Preparation  of  the  Steel  for  Rolling. 

SECTION  I.        INGOTS  AND  THEIR  DEFECTS: 

1.  Preparation  of  Ingots 342 

2.  Ingot  Defects 342 

3.  The  Nature  of  the  Cooling  of  an  Ingot 343 

a.  Pipes 343 

i.    Methods  of    Reducing  Waste  due  to 

the  Pipe 346 

b.  Blow  Holes 346 

c.  Crystallization 348 

d.  Segregation 348 

e.  Checking  and  Scabs 349 

f .  Slag  Inclusions 349 

4.  Size  and  Shape  of  Ingots 352 

SECTION  II.      THE  CONSTRUCTION  OF  THE  SOAKING  PIT: 

1.  General  Features  of  the  Pit 352 

2.  Arrangement  of  the  Pits 353 

3.  Equipment  for  Handling  Ingots 353 

4.  Construction  of  the  Pits 353 

a.  The  Air  Regenerators 355 

b.  The  Pit  Covers ,..  356 

c.  Fuel  and  Air  Valves,  etc 357 

d.  Stack-Flues  and  Stack 357 

e.  The  Course  of  the  Gases  Through  the  Pits 358 

5.  Eight  Ingot  Pits 358 

6.  Making  up  the  Bottom  of  the  Pit 358 


TABLE  OF  CONTENTS  xxvii 


SECTION  III.    SOAKING  THE  INGOTS  FOR  ROLLING: 

1.  Charging  the  Ingots 359 

2.  Heating  the  Ingots 360 

a.  Week-end  Charges 360 

b.  Soaking  Hot  and  Cold  Ingots 360 

c.  Soaking  Hot  Spring  Steel 361 

d.  Soaking  Low  Carbon  Hot  Steel 361 

e.  Soaking  Medium  Steels 361 

f.  Soaking  Screw  Stock . . .  361 

g.  Soaking  Alloy  Steels 362 

3.  Drawing  the  Ingots 362 

4.  Heat  Balance  of  Pits 362 

5.  Disposition  of  Ingot  Products 363 

CHAPTER  V.    The  Rolling  of  Blooms  and  Slabs. 
SECTION  I.        INTRODUCTORY: 

1.  Outline  of  the  Plan  of  Study 364 

2.  Blooms,  Slabs  and  Billets 365 

SECTION  II.      SOME     GENERAL'    FEATURES     PERTAINING     TO 
BLOOMING  MILLS: 

1.  Size  of  Blooming  Mills 366 

2.  Types  of     Bloomers,    Their  Advantages  and     Dis- 

advantages   366 

3.  Drive  for  Reversing  Mills 368 

SECTION  III.     AN  EXAMPLE  OF  REVERSING  MILLS— THE  40" 
MILL  AT  DUQUESNE: 

1.  The  Engine 368 

2.  Driving  Connections 368 

3.  Pinions  and  Pinion  Housings 369 

4.  Spindles  and  Coupling  Boxes 369 

5.  Roll  Housings 370 

6.  Rolls 371 

7.  Roll  Bearings 371 

8.  Hydraulic  Shears 372 

9.  Steam  Shears 372 

10.  Manipulator 373 

11.  Design  of  the  Rolls 373 

12.  Operation  of  Rolling 375 

SECTION  IV.     EXAMPLE  OF  A  THREE-HIGH  BLOOMING    MILL: 

1.  Plan  of  Study 377 

2.  The  40"  Three-high  Mill  at  Edgar  Thomson 377 

a.     The  Engine  and  Connections 378 


xxviii  TABLE  OF  CONTENTS 

SECTION  IV.— Continued. 

b.  The  Pinions  and  Spindles 378 

c.  The  Roll  Housings 378 

d.  The  Rolls 378 

e.  Lifting  Tables 380 

3.     Roll  Design  for  Three-high  Bloomers 381 

a.     An   Example   of   Roll    Design   for    Three-high 

Blooming  Mill 381 

SECTION  V.       THE  ROLLING  OF  SLABS: 

1.  The  Rolling  of  the  Slab 385 

2.  The  32"  Mill   at   Homestead   as   an  Example  of  a 

Slabbing  Mill 385 

a.  The  Horizontal  Mill 385 

b.  The  Vertical  Mill 386 

3.  Precautions  to  be  Observed  in  Rolling  Slabs 387 

4.  Removal  of  Scale 388 

5.  Shearing  Slabs  at  32"  Mill 389 

CHAPTER  VI.     The    Rolling    of    Billets    and    Other    Semi- 
Finished  Products. 

SECTION  I.        THE  THREE-HIGH  BILLET  MILL: 

1.  General  Features  of  Rolling  Billets 391 

2.  Example  of   Three-High   Billet  Mill— The    28"  Mill 

at  Duquesne 391 

a.  Engine 391 

b.  Drive 392 

c.  Pinions  and  Their  Housings 392 

d.  Housings  and  Roll  Bearings 393 

e.  Rolls 393 

f.  Guide  Cages 395 

g.  Tables 395 

SECTION  II.      THE  CONTINUOUS  BILLET  MILL: 

1.  General  Features  of  the  Continuous  Mill 397 

2.  Advantages  and  Disadvantages  of  Continuous  Mills . .  397 

3.  Example  of  Continuous  Billet  Mill 398 

a.  Drive 398 

b.  Pinions  and  Housings 399 

c.  Rolls  and  Housings 399 

i.     Adjustment  of  Rolls 399 

d.  Arrangement  of   Roll  Stands   and  Guides 400 

e.  The  Rolls 400 

f .  Cropping  Shears 401 

g.  Flying  Shears 404 

h.    Hot  Beds..  404 


TABLE  OF  CONTENTS  xxix 

SECTION  III.     ROLLING  OF  SHEET  BARS  AND  SKELP: 

1 .  Difficulties  and  Methods  of  Rolling  Semi-Finished  Flats  406 

2.  The  Tongue  and  Groove  Pass 406 

3.  Sheet  Bar 408 

4.  The  21"  Mill  at  Duquesne .-,.'.:.. 408 

a.  The  Layout  for  the  Mill 409 

b.  Arrangement  of  the  Roll  Tables 409 

c.  Hot  Saws  and  Shears 410 

d.  Drive 410 

e.  Pinions  and  Housings 411 

f .  Rolls  and  Roll  Housings 412 

SECTION  IV.     SOME  GENERAL  PRECAUTIONS  TO  BE  OBSERVED 
IN  ROLLING  SEMI-FINISHED  PRODUCTS: 

1.  Reasons  for  Studying  Defects 413 

2.  Rough  Surface  Due  to  Scale ".  413 

3.  Cobbling 414 

4.  Laps 414 

5.-   Collar  Marks 414 

6.  Guide  Marks 415 

7.  Ragging  Marks 415 

8.  Off  Size 415 

9.  Unequal  Draughts 415 

10.  Seams 415 

11.  Slivers < 415 

12.  Scabs 415 

13.  Shearing  Defects 415 

14.  Splits  or  Cracks  in  Billets  and  Blooms 417 

15.  Inspection 417 

CHAPTER  VII.     The  Rolling  of  the  Heavier  Finished  Products 
—Plates. 

SECTION  I.        PREPARATION    OF    THE     STEEL    FOR    ROLLING 
FINISHED  PRODUCTS: 

1.  Reheating 418 

2.  Types  of  Reheating  Furnaces 419 

a.  The  Regenerative  Reheating  Furnace 419 

b.  The  Recuperative,  or  "Continuous"  Furnace. . .  421 

3.  The  Advantages  of  Continuous  Reheating  Furnaces. . .  421 

SECTION  II.      THE  ROLLING  OF  SHEARED  PLATES: 

1.  Methods  of  Rolling  Plates 423 

2.  The    140"    Mill  at  Homestead  as  an  Example  of  a 

Sheared  Plate  Mill 423 

a.     The  Drive  and  Connections 424 


xxx  TABLE  OF  CONTENTS 

SECTION  II.— Continued. 

3.  Difficulties  in  Rolling  Sheared  Plates 425 

4.  The  Rolling  Process 426 

5.  Cooling  and  Straightening , 427 

6.  Laying-out  and  Stamping 427 

7.  Test  Pieces 429 

8.  Shearing 429 

a.    Shearing  Tolerances , . .  430 

9.  Size  Inspection 430 

10.  Weighers ....  430 

11.  Checkers 430 

12.  Slip  Maker 431 

13.  Recorder 431 

SECTION  III.    UNIVERSAL  MILL  PLATES: 

1 .  The  48"  Mill  at  Homestead  as  an  Example  of  Universal 

Plate  Mills 431 

2.  The  Operation  of  Rolling 432 

3.  Straightening,  Marking  and  Shearing  U.  M.  Plate . ." . .  433 

4.  Advantages  of  Universal  Mill  Plates 433 

5.  Physical  Properties  of  Plates 433 

6.  Inspection  of  Plates 434 

CHAPTER  VIII.    The  Rolling  of  Large  Sections. 
SECTION  I.        RAILROAD  RAILS: 

1.  Development  of  Rail  Manufacture 436 

2.  Methods  of  Rolling  Rails 437 

3.  How  to  Study  Roll  Design 438 

4.  Precautions  to  be  Observed  in  Designing  the  Rolls. . .  438 

5.  Stages  of  Reduction 439 

6.  The  Different  Steps  in  the  Design  of  the  Rolls 439 

a.  The  Section 439 

b.  The  Cold  Templet 439 

c.  The  Hot  Templet 441 

d.  The  Pass  Templet 441 

e.  Preparation  for  the  Rolling 443 

7.  The  Diagonal  Method 447 

8.  The  Mills 447 

9.  Rolling  Heavy  Rails 448 

10     Unavoidable  Variations 448 

11.  The  Various  Steps  in  Shaping  of  Rails 449 

12.  Cutting 450 

13.  Recording 451 

14.  Finishing  and  Inspection 451 

15.  Light  Rails 452 


TABLE  OF  CONTENTS  xxxi 

SECTION  II.      THE  SHAPING  OF  RAIL  JOINTS: 

1.  Rolling  Rail  Joints 454 

2.  Methods  of  Finishing  Rail  Joints 458 

a.  Cold  Worked  Bars 459 

b.  Cold  Worked  and  Annealed  Bars 459 

c.  Hot  Worked  Bars 460 

d.  Hot  Worked  and  Oil  Quenched 461 

3.  The  Edgar  Thomson  Splice  Bar  Shop 458 

SECTION  III.    STRUCTURAL  AND  OTHER  SHAPES: 

1.  Plan  of  Study 461 

2.  Angles,  Methods  of  Rolling 462 

a.    The  Three  Methods  Compared  462 

3.  The  Channel 464 

4.  Beams,  Ties,  and  Piling 464 

5.  Zees  and  Tees 466 

6.  Finishing  Sections 466 

7.  Rounds 467 

8.  Cutting  and  Straightening  Rounds 468 

9.  Flats 468 

10.  Hexagons 469 

11.  Deformed  Bars 469 

CHAPTER  IX.  The  Rolling  of  Strip  and  Merchant  Mill  Products 

SECTION  I.        STRIP,  OR  HOOP,  MILLS  AND  THEIR  PRODUCTS: 

1.  Meaning  of  the  Word  Hoop 470 

2.  Hoop  as  a  Rolling  Specialty 470 

3.  The  Carnegie  Hoop  Mills 470 

4.  Methods  of  Rolling  Hoop 471 

5.  Precautions  Required  in  Rolling  Hoop. 471 

6.  Finishing  Hoop 473 

SECTION  II.      MERCHANT  MILLS: 

1.  What  the  Merchant  Mill  Is 474 

2.  Kinds  of  Merchant  Mills 474 

a.  The  Guide  Mill 475 

b.  The  Belgian  and  Looping  Mills 477 

c.  The  Semi-continuous  or  Combination  Mill. . . .  477 

d.  The  Cross  Country  Mill 479 

3.  Future  Development 479 

SECTION  III.     DESIGNING  ROLLS  AND  MAKING  UP  SCHEDULES 
FOR  MERCHANT  MILLS: 

1.  Roll  Designing  for  Merchant  Mills 482 

2.  Economic  Features  of  Roll  Designing 482 

3.  The  Order  in  the  Office 484 

4.  The  Order  at  the  Mill— Size  of  Billet  or  Bloom . .  486 


TABLE  OF  CONTENTS 


SECTION  IV.     ROLLING  PRACTICE  IN  MERCHANT  MILLS: 

1.  The  Roller— His  Importance 487 

2.  Precautions  in  Rolling 487 

3.  Rolling  Defects 488 

4.  Two  Different  Finishes 489 

a.  Common  Finish 489 

b.  Special  Finish 489 

I 

SECTION  V.       SHEARING    AND    BUNDLING    MERCHANT    MILL 
PRODUCTS: 

1.  The  Methods  of  Shearing  and  Bundling 490 

2.  Duties  of  the  Shear  Foreman 490 

3.  Bundling  Export  Material 491 

4.  Special  Bundling 491 

5.  Handling  the  Material  in  the  Warehouse 491 

6.  Straightening 492 

7.  Invoicing 492 

SECTION  VI.     INSPECTION  DEPARTMENT  OF  A  MERCHANT  MILL 
PLANT: 

1.  The  Inspection  Department 493 

2.  Function  of  the  Inspection  Department 493 

3.  Surface  Defects 494 

a.  Buckles  and  Kinks 494 

b.  Fins 494 

c.  Underfills 494 

d.  Slivers 494 

e.  Laps 494 

f .  Seams 494 

g.  Burned  Steel 495 

h.    Roll  Marks 495 

i.     Finish 495 

j.     Pipe 495 

4.  Testing  for  Defects 495 

5.  Other  Duties  of  Inspectors 495 

6.  Manner  of  Gauging  Different  Sections 496 


CHAPTER  X.     Circular  Shapes. 

SECTION  I.        SOME  GENERAL  FEATURES  PERTAINING  TO  THE 
ROLLING  OF  CIRCULAR  SHAPES: 

1.  The  Rolling  of  Circular  Shapes 497 

2.  Preparing  the  Blanks 497 


TABLE  OF  CONTENTS 


SECTION  II.      THE   CARNEGIE   SCHOEN  METHOD  FOR  MANU- 
FACTURING STEEL  WHEELS: 

1.     The  Carnegie  Schoen  Method 498 

a.  Forging  the  Blanks: 

i.     First  Method  of  Forging 499 

ii.     Second  Method  of  Forging „ . . . .  500 

b.  Rolling  the  Forged  Blank: 

i.     The  Rolling  Mill 500 

ii.     The  Rolling  Process 503 

iii.    Effect  of  the  Rolling 504 

c.  Punching  Web  Holes  and  Coning 504 

d.  Inspection  of  Carnegie  Schoen  Wheels 504 

e.  Heat  Treating  Car  Wheels 506 

2.     The  Forging  of  Circular  Shapes 507 


CHAPTER  XI.     Forging  of  Axles,  Shafts  and  Other  Round 
Shapes. 

SECTION  I.        HOWARD  AXLE  WORKS  AS  AN  EXAMPLE  OF  A 
FORGING  SHOP: 


1.  The  Plant  and  its  Equipment 508 

2.  Precautions  to  be  Observed  in  the  Manufacture  of  Axles  508 

3.  Inspection  of  the  Blooms 509 

4.  Heating  the  Blooms 509 

5.  The  Rolling  and  Forging  Operation 509 

a.     Advantages  of  the  Method 510 

SECTION  II.      FINISHING  PROCESSES  FOR  FORCINGS: 

1.  Straightening 511 

2.  Cutting-off  and  Centering 511 

3.  Rough  Turning 512 

4.  Hollow  Boring 512 

a.  Piping  and  Segregation 512 

b.  Strength  and  Weight 512 

c.  Hollow  Boring  and  Heat  Treating 513 

5.  The  Heat  Treating  Plant 513 

a.  The  Furnaces 513 

b.  The  Quenching  Tanks : 514 

c.  The  Testing  Equipment '. 515 

d.  Advantages  of  Heat  Treating  Axles 515 


xxxiv  TABLE  OF  CONTENTS 


PART  III. 

THE    CONSTITUTION,  HEAT  TREATMENT 
AND  COMPOSITION  OF  STEEL. 

1.     INTRODUCTORY 516 

CHAPTER  I.    The  Constitution  and  Structure  of  Plain  Steel. 

SECTION  I.        STEEL  AS  AN  ALLOY  OF  IRON  AND  CARBON: 

1.  The  Constituents  of  Steel 518 

a.  Ferrite 518 

b.  Cementite 518 

c.  Pearlite 520 

2.  Manner  of  Freezing  of  Solutions  and  Alloys 520 

a.  An  Example  of  the  First  Class  of  Solutions .  .  .  520 

b.  Example  of  the  Second  Class  of  Solutions — Salt 

and  Water 521 

c.  Lead  and  Tin  Solutions  as  Another  Example  of 

the  Second  Kind  of  Freezing 523 

d.  The  Iron-Carbon  Eutectic 524 

i.     Formation  of  Pearlite  and  the  Eutectoid. .  525 

3.  Structural  Composition  of  Slowly  Cooled  Steel 526 

a.     Effect  of  the  Constituents   Formed    Upon    the 

Physical   Properties 526 

SECTION  II.      THERMAL  CRITICAL  POINTS  OF  STEEL: 

1 .  Nature  of  Critical  Points  or  Ranges  of  Steel 527 

2.  Thermal    Critical    Point  for    Eutectoid  Steel 527 

3.  Thermal  Critical  Points  for  Pure  Iron 528 

4.  Thermal  Critical  Points  of  Low  Carbon  Steel 528 

5.  Thermal  Critical  Points  of  Medium  Carbon  Steel. .  .  528 

6.  The  Carbon-Iron  Diagram  for  Steels    and   Methods 

of  Notation 529 

7.  The  Position  of  the  Critical  Ranges 530 

8.  Changes  at  the  Thermal  Critical  Points 530 

a.  Changes  at  AS 530 

b.  Changes  at  Ag 531 

i.     The  Magnetic  Properties 531 

c.  Changes  at  AS,  2 531 

d.  Changes  at  AI 53 1 

9.  Causes  of  the  Thermal  Critical  Points  in  Steel...  532 


TABLE  OF  CONTENTS 


SECTION  III.     THE  CRYSTALLINE  STRUCTURE  OF  STEEL: 

1 .  Crystals  and  Grains 533 

2.  Crystallization  of  Steel:  533 

a.  Crystallization  of  Eutectoid  Steels 534 

b.  Crystallization  of  Hypo-Eutectoid  Steel 534 

c.  Crystallization  of  Hyper-Eutectoid  Steels 535 

d.  The  Effect  of  Work  on  Grain  Size 535 

e.  Crystalline  Changes  on  Heating  Steel:  535 

i.     Crystalline  Refinement  on  Heating 536 

3.  Practical  Importance  of  Grain  Structure 537 

4.  Summary  of  Chapter  I 538 

CHAPTER  II.     Heat  Treating  Theory  and  Practice. 

INTRODUCTION 539 

SECTION  I.        ANNEALING: 

1.  The  Annealing  Operation 539 

2.  Purpose  of  Annealing 539 

3.  True  Annealing  and  "Process"  or  "Works"  Annealing  540 

4.  Heating  for  True  Annealing:  540 

a.     Importance  of  Time  in  Heating  for  Annealing. .  542 

5.  Cooling 542 

a.  Effect  of  Cooling  on  the  Net- Work 543 

b.  The  Effect  of  Cooling  Upon  Pearlite 543 

c.  Other  Factors 545 

d.  Methods  of  Cooling 545 

e.  Combination  Methods  of  Cooling 545 

6.  Double  Annealing 546 

7.  Box  Annealing 546 

8.  Annealing  Hyper-Eutectoid  Steels 547 

9.  Normalizing  and  Spheroidizing 547 

SECTION  II.       HARDENING: 

1.  The  Hardening  Operation 548 

2.  Heating  for  Hardening 548 

3.  Cooling  for  Hardening 549 

a.  Cooling  or  Quenching  Media 551 

b.  Combination  Methods  of  Quenching 551 

c.  Manner  of  Quenching 553 

4.  Progressive  Hardening 553 

5.  Hardening  Eutectoid  Steels 553 

6.  Hardening  Hyper-Eutectoid  Steels 553 

7.  Hardening  Hypo-Eutectoid  Steels 554 


TABLE  OF  CONTENTS 


SECTION  III.     THE  TEMPERING  OF  HARDENED  STEEL: 

1.  The  Tempering  Process 554 

2.  Nature  and  Theory  of  Tempering 555 

3.  Methods  of  Determining  Tempering  Temperatures.  556 

4.  Influence  of  Time  in  Tempering 557 

5.  Physical   Properties   Affected   by  Tempering 557 

6.  Tempering    the      Steels    of      Different      Structural 

Composition 557 

a.  Tempering  Austenitic  Steels 558 

b.  Tempering  Martensitic  Steels 558 

c.  Tempering  Troostitic  Steels 558 

d.  Sorbite..  559 


SECTION  IV.    THE  TOUGHENING  OF  STEEL: 

1.  Toughening  Defined 559 

2.  Benefits   of  Toughening 559 

3.  Quenching  for  Toughening 559 

4.  Change  of  Constituents  Due  to  Toughening  Fig.  118. .  560 

5.  Physical  Properties  of  Toughened  Steel  Tab.  62 561 


SECTION  V.     CASE  HARDENING: 

1.  The  Process  of  Carburizing  Iron 562 

2.  Application  of  Case  Hardening 562 

3.  The  Two  Periods  of  the  Case  Hardening  Process ....  562 

4.  Kinds  of  Steel  Suitable  for  Case  Hardening 563 

5.  Case  Hardening  Properties  of  the  Elements: 

a.  Carbon 563 

b.  Manganese 563 

c.  Silicon 563 

d.  Phosphorus  and  Sulphur 563 

e.  Nickel 563 

f .  Vanadium 563 

g.  Chromium 564 

6.  The  Carburizing  Agent 564 

7.  Carburizing  Materials: 564 

a.  Packing  and  the  Action  of  Charcoal  Carburizer  564 

b.  Carburizing  Mixtures  and  Compounds 565 

8.  Heating  the  Carburizing  Pack 566 

a.    Controlling  the  Temperature 567 

9.  Removal    of    the   Articles    from   the    Boxes    After 

Carburizing 567 

10.  Heat  Treatment  of  Case  Hardened  Articles 568 

11.  Superficial  Hardening 568 


TABLE  OF  CONTENTS  xxxvii 

CHAPTER  III.  Constituent  Elements  of  Commercial  Carbon 
Steel  and  Their  Influence  Upon  Its 
Mechanical  Properties. 

INTRODUCTORY 569 

1.  Properties  of  Iron 569 

2.  Effect  of  Carbon 570 

3.  Influence  of  Manganese 570 

a.  Influence  of   Manganese  in  Heat  Treatment . . .  571 

b.  Influence  of  Manganese  on  Sulphur 572 

4.  Influence  of  Sulphur 572 

a.  Why  Manganese  Neutralizes  Effect  of  Sulphur .  572 

b.  Uses  for  Sulphur  in  Steel 572 

5.  Influence  of  Phosphorus 573 

a.    The  Two  Evils  of  Phosphorus 574 

6.  Influence  of  Silicon 574 

7.  The  Influence  of  Oxygen 575 

8.  Combined  Effect  of  the  Elements  on  Tensile  Strength 

of  Steel 575 

9.  The  Influence  of  Copper 576 

10.  Influence  of  Tin 577 

11.  Influence  of  Arsenic 577 

CHAPTER  IV.    Alloy  Steels. 

SECTION  I.        INTRODUCTORY. 

1.  Definitions 578 

2.  Carnegie  Types  and  Grades 579 

SECTION  II.      NICKEL  STEEL: 

1.  Manufacture  of  Simple  Nickel  Steel 580 

2.  The    Different    Nickel    Steels  and    Their    General 

Characteristics 581 

3.  Reasons  for  These  Peculiarities  of  the  Nickel  Steels . .  582 

4.  Structural  Changes  Due  to  Nickel 584 

a.  Pearlitic-Nickel  Steels 584 

b.  Martensitic-Nickel  Steels 584 

c.  Austenitic-Nickel  Steels 584 

5.  The  Constitutional  Theory  of  Ternary  Steels 584 

6.  Heat  Treating  Pearlitic  Nickel  Steels 585 

SECTION  III.    CHROME  STEEL: 

1.  The  Manufacture  of  Simple  Chromium  Steels 587 

2.  Influence  of  Chromium 587 

a.    The   Microscopic   Constituents   of  the  Chrome 

Steels 588 

3.  Uses  of  the  Simple  Chrome  Steels : 589 

4.  Heat  Treatment  of  Chrome  Steel. .  589 


xxxviii  TABLE  OF  CONTENTS 

SECTION  IV.     CHROME — NICKEL  STEELS: 

1.  Influence  of  Chromium  and   Nickel  When  Combined.  590 

2.  Types  of  Chrome-Nickel  Steel 590 

3.  Mayari  Steel 591 

4.  Uses  of  Chrome-Nickel  Steels 591 

5.  Heat  Treatment  of  Chrome-Nickel  Steels 592 

6.  Physical  Properties  of  Chrome-Nickel  Steels 593 

SECTION  V.       VANADIUM  STEELS: 

1.  Simple  Vanadium  Steels 595 

2.  Influence  of  Vanadium .-  595 

SECTION  VI.     CHROME-VANADIUM  STEELS: 

1.  Effect  of    Combining  Chromium  and  Vanadium 596 

2.  Properties  and  Uses  of  Chrome-Vanadium  Steels 596 


PART  1. 

THE  MAKING  OF  STEEL. 

CHAPTER  1. 

SOME  FUNDAMENTAL  PRINCIPLES  OF  PHYSICS  AND 
CHEMISTRY. 

SECTION  1. 

INTRODUCTION. 

1.  Iron,  the  Master  Metal:  In  beginning  this  very  brief  study 
of  the  metallurgy  of  the  most  important  metal  of  a  metallic  age,  it  is  difficult 
to  refrain  from  pointing  out  a  few  of  the  qualities  that  have  made  iron  the 
master  metal,  although  its  importance  really  needs  no  comment  here.  A 
little  reflection  shows  it  to  be  as  vital  to  modern  civilization  as  air  and  water 
are  to  life;  and  it  has  become  so  common  that,  like  air  and  water,  its  true 
importance  is  lost  sight  of  by  most  people,  who  look  upon  its  abundance  as 
a  matter  of  course  and  value  it  accordingly .  No  other  one  metal  has  contributed 
so  much  to  the  welfare  and  comfort  of  man.  There  is  scarcely  an  article 
used  in  our  daily  lives  that  has  not  been  produced  from  iron  or  by  means 
of  it.  Consider  bread  as  an  example.  Plows  made  of  iron  turn  the  soil, 
harrows  of  iron  level  it,  and  drills  of  iron  sow  the  seed;  machines  of  iron  harvest 
the  wheat  and  thrash  it;  rolls  of  iron  crush  the  grain  to  separate  the  flour; 
engines  of  iron  bring  the  flour  to  our  homes,  where  it  is  made  into  dough  in 
iron  pans  and  baked  in  an  iron  stove;  finally  the  bread  is  sliced  from  the  loaf 
with  an  iron  knife,  and  served  to  us  at  a  table  made  with  iron  tools.  It  has  no 
exact  substitute  in  nature,  and  without  it  most  of  our  modern  conveniences 
would  have  been  impossible  of  development.  The  railroads,  the  automobile, 
and  the  watch  are  three  of  the  many  notable  examples  of  such  conveniences 
No  other  metal  is  capable  of  giving  the  great  range  in  physical  properties, 
that  makes  iron  available  for  an  almost  unlimited  number  of  purposes.  Thus, 
from  our  towering  skyscrapers,  our  massive  bridges  and  our  immense  ships, 
where,  as  great  beams,  cables  and  plates,  it  supports  loads  almost  greater 
than  the  mind  can  conceive,  we  can  trace  it  even  to  our  parlors,  where,  as 
invisible  hairpins,  it  supports  milady's  tresses  and,  as  the  strings  of  her  piano, 
sends  forth  at  her  magic  touch  sweet  sounds  of  melody.  One  property  which 
it  possesses  in  a  far  greater  degree. than  any  of  the  other  metals  is  that  of 
magnetism.  This  property  is  so  pronounced  in  iron  and  so  slight  in  other 
metals  that,  from  a  practical  viewpoint,  iron  and  one  of  its  compounds  may 
be  considered  as  the  only  magnetic  substances.  Hence,  our  modern  magnetic 


2  MFTA-LLURGY,   MATTER 


and  electrical' Appliances  "are  <kpendent  upon  this  one  metal;  and  we  find 
it  forming  the  essential  parts  of  the  dynamo,  the  electric  motor,  the  telegraph, 
the  telephone,  the  wireless  telegraph,  the  compass,  and  a  large  number  of  other 
instruments  of  less  importance.  And  so  we  might  continue  at  great  length 
upon  this  one  topic  of  the  importance  of  iron,  but  our  time  is  too  short  to 
permit  our  giving  much  of  it  to  a  theme  which  the  reader  may  develop  for 
himself.  Hastening  on,  then,  to  more  important  matters,  we  find  the  first 
question  that  confronts  us  is,  What  is  Metallurgy? 

Metallurgy:  In  general,  Metallurgy  is  defined  as  the  science  which 
deals  with  the  preparation  of  the  metals  and  their  adaptation  to  the  uses 
for  which  they  are  intended.  It  is  an  advanced  and  specialized  science, 
hence  a  difficult  one.  Even  a  slight  understanding  of  the  subject  requires 
a  previous  knowledge  of  the  fundamental  sciences  of  Physics  and  Chemistry. 
For  those  who  may  not  have  had  the  necessary  preparation  in  these  pre- 
requisites, this  study  is. becomingly  introduced  by  a  brief  consideration  of 
some  of  the  more  important  principles  of  these  two  sciences.  To  present 
these  principles  in  as  concise  and  simple  a  manner  as  possible  is  the  object 
of  this  chapter. 

Matter :  Through  the  various  senses  of  sight,  touch  and  hearing,  the 
human  intellect  becomes  aware  of  the  existence  of  things  which,  collectively, 
are  called  matter.  Limited  portions  of  space  that  contain  matter  are 
termed  bodies,  and  the  different  kinds  of  matter  are,  in  general,  spoken 
of  as  substances.  Matter  is  a  fundamental  thing  and  cannot  be  accurately 
defined.  It  is  described  by  its  properties,  which  will  be  discussed  later. 

The  Fundamental  Law  and  the  States  of  Matter:  Certain  facts 
about  matter,  however,  are  plainly  evident.  It  occupies  space,  and  can 
be  neither  increased  nor  decreased  in  amount.  These  last  two  facts  are 
commonly  known  as  the  Law  of  the  Conservation  of  Matter.  It  exists 
in  any  one  of  three  states;  solids,  which  have  definite  masses,  sizes  and 
shapes;  liquids,  which  have  definite  masses  and  sizes  but  not  form;  and  gases, 
which  possess  definite  masses  only.  A  common  example  is  water,  which 
at  ordinary  temperatures  exists  in  all  three  states;  namely,  ice,  water  and 
vapor.  Liquids  and  gases  together  are  called  fluids  on  account  of  their 
flowing  properties,  and  in  many  instances  they  are  subject  to  the  same  laws. 
They  are  distinguished  from  each  other  by  their  relative  compressibility. 
Liquids  are  but  slightly  compressible,  while  gases  are  highly  compressible. 
The  volume  of  a  gas  varies  inversely  as  the  pressure  applied  to  it.  For 
example,  if  a  certain  mass  of  gas  has  a  volume  of  10  cu.  ft.  under  a  pressure  of 
100  Ibs.,  the  same  mass  of  gas  will  occupy  but  5  cu.  ft.  at  200  Ibs.  pressure. 

Molecules:  Furthermore,  while  the  conception  may  seem  difficult  to 
establish  as  a  fact,  there  are  strong  reasons  for  believing  that  the  relatively 
large  bodies,  in  which  form  matter  makes  itself  evident  to  the  human 
are  composed  of  minute  particles,  called  molecules.  This  belief  is 


MOLECULES 


founded  upon  many  facts,  and  can  be  arrived  at  by  some  such  process  of 
reasoning  as  follows:  Mental  conception  concerning  the  constitution  of 
matter  may  be  based  on  either  one  of  two  hypotheses;  namely,  that  matter 
is  infinitely  divisible  or  that  it  is  made  up  of  small  particles.  According 
to  the  first  hypothesis,  a  body  of  matter  could  be  divided  indefinitely,  if 
means  were  available  to  make  such  a  process  possible,  without  changing 
any  of  its  characteristics,  except  its  size;  that  is,  a  piece  of  chalk,  for 
example,  would  remain  chalk  even  as  the  particles  resulting  from  the  infinite 
division  approached  zero  in  size  and  weight.  This  retention  of  original 
characteristics  would  imply  that  each  individual  kind  of  matter,  the  chalk 
in  the  present  instance,  is  an  elementary  substance.  But  this  conclusion 
is  contrary  to  the  facts,  for  it  is  a  matter  of  common  knowledge  that  many 
substances  like  iron  ore,  limestone,  sugar,  etc.,  are  composed  of  substances 
quite  different  from  the  original.  Thus,  through  the  application  of  heat 
alone,  limestone  and  sugar  are  decomposed,  the  former  into  quick  lime 
and  carbonic  acid  gas,  and  the  latter  into  carbon,  or  charcoal,  and  water. 
Only  the  second  hypothesis  remains,  and  it  agrees  with  these  facts,  for  ft 
assumes  that  the  larger  masses  of  limestone  and  sugar,  so  evident  to  our 
senses,  are  made  up  of  small  particles,  each  of  which  is  composed  of 
portions  of  these  simpler  things  into  which  the  limestone  and  sugar  are 
decomposed  by  the  heat.  These  ultimate  particles  of  the  different 
substances  are  called  molecules,  which  are,  therefore,  defined  as  the 
smallest  particles  of  a  substance  that  retain  the  characteristics  of  that 
substance. 

Sciences  of  Matter:  Two  great  classes  of  matter  are  evident;  animate 
or  living  matter,  such  as  the  living  bodies  of  plants  and  animals,  and 
inanimate  matter,  such  as  glass,  water,  air,  etc.  Animate  matter  is  treated 
of  by  the  sciences  of  Biology,  Zoology  and  Botany;  inanimate,  by  Physics 
and  Chemistry,  formerly  included  under  the  one  head  of  Natural  Philosophy. 
Thus,  Metallurgy  may  be  looked  upon  as  a  highly  specialized  branch  of 
Natural  Philosophy.  All  these  sciences  are  so  closely  related  that  a 
knowledge  of  all  is  essential  to  a  complete  understanding  of  any  one. 


SECTION   II. 

SOME   PHYSICAL  PROPERTIES   OF   MATTER. 

Properties :  That  a  better  understanding  of  matter  may  be  obtained 
from  a  study  of  its  properties  has  already  been  indicated.  By  properties 
is  meant  those  characteristics  by  which  the  different  kinds  of  matter  are 
distinguished  and  by  which  it  may  be  described  and  defined.  They  are 
of  two  classes, — namely,  general  and  special.  General  properties  are 
common  to  all  matter,  while  special  properties  are  peculiar  to  certain  kinds 
of  matter  only.  The  general  properties  are  as  follows: 

Inertia:  This  property  causes  matter  to  resist  any  attempt  to  change 
its  state  of  rest  or  motion. 


PHYSICAL  PROPERTIES 


Extension  is  that  property  by  virtue  of  which  matter  occupies  space. 
There  are  two  systems  of  measuring  extension,  the  English  and  the  metric. 
In  the  English  system,  the  linear  unit  is  the  yard,  while  the  volumetric 
units,  as  established  by  custom,  are  the  gallon,  the  bushel,  and  the  cubic 
yard.  Corresponding  units  in  the  metric  system  are  the  meter=l. 09361 
yards=39. 37  inches;  the  kilometer=.62137  mile;  the  liter=.26417  gallon= 
1.0567  quarts,  liquid,  or  .908  quart,  dry;  and  the  cubic  meter=1.308  cubic 
yards. 

Mass  refers  to  the  amount  of  matter.  It  is  measured  in  grams,  which 
is  the  mass  of  one  cubic  centimeter  of  pure  water  at  the  temperature  of  its 
greatest  density,  4°  centigrade.  Commercially,  the  unit  is  the  kilogram, 
equal  to  1000  grams.  From  a  scientific  standpoint  there  is  no  exact  English 
equivalent,  because  weight  involves  the  force  of  gravity,  which  may  vary, 
whilst  mass  is  constant.  However,  the  pound  has  been  standardized  so 
that  one  kilogram=2. 20462  pounds. 

Density  is  the  weight  or  mass  of  a  unit  volume  of  matter.  It  is  usually 
expressed  in  grams  per  cubic  centimeter. 

Specific  Gravity  is  the  number  of  times  a  body  is  heavier  than  an 
equal  volume  of  some  substance  used  as  a  standard.  For  liquids  and  solids 
this  standard  is  water;  for  gases  it  is  air  or  hydrogen.  In  the  metric  system 
density  and  specific  gravity  are  numerically  the  same,  since  the  weight  of 
one  cubic  centimeter  of  water  is  one  gram. 

Porosity:  All  matter  is  porous.  The  molecules,  it  is  thought,  are 
separated,  even  in  the  densest  materials,  by  spaces  larger  than  the  mole- 
cules themselves. 

Impenetrability:  Two  bodies  of  matter  cannot  occupy  the  same  space 
at  the  same  time,  and  to  this  property  of  matter  the  term  impenetrability 
is  applied. 

Special  Properties:  The  chief  special  properties  of  matter,  some  of 
which  are  of  supreme  importance  in  the  manufacture  of  steel,  are  as  follows: 

Cohesion  and  Adhesion :  According  to  the  law  of  gravitation,  every 
particle  of  matter  in  the  physical  universe  attracts  every  other  particle 
with  a  force  whose  direction  is  that  of  a  line  joining  the  two  particles  and 
whose  magnitude  varies  directly  as  the  product  of  the  two  masses,  and 
inversely  as  the  square  of  the  distance  between  them.  Applied  to  molecules, 
this  attraction  is  known  as  cohesion  and  adhesion;  the  former  is  the 
attraction  of  molecules  of  the  same  kind  for  each  other,  the  latter,  the 
attraction  of  unlike  molecules.  The  clinging  of  a  drop  of  water  to  the  end 
of  a  glass  rod  exemplifies  both  of  these  forces. 

Elasticity  is  the  power  of  matter  to  assume  its  original  shape  after 
having  been  distorted.  The  property  of  cohesion  causes  all  bodies  to  resist 
change  in  form,  but  only  solids  have  elasticity  of  form.  When  a  solid  body 


PHYSICAL  PROPERTIES 


is  deformed,  the  resistance  it  offers  is  called  the  stress;  the  deformation 
which  produces  this  stress  is  called  the  strain.  Hooke's  law  states  that, 
up  to  the  elastic  limit,  the  strain  is  proportional  to  the  stress.  In  practice, 
the  stress  is  measured  in  terms  of  a  force  or  forces  applied  externally 
to  the  body  being  tested.  There  are  four  methods  of  calling  forth  the 
elasticity  of  bodies:— namely,  by  pressure,  by  stretching,  by  bending  and 
by  twisting.  Stretching  and  bending  are  the  methods  most  commonly 
employed  in  testing  the  elasticity  of  steel. 

Plasticity  is  the  opposite  of  elasticity.  A  plastic  body  once  distorted 
will  not  regain  its  original  shape. 

Ductility  is  sometimes  defined  as  the  property  by  virtue  of  which 
matter  may  be  drawn  into  fine  wires.  As  the  term  is  employed  in  the 
testing  of  steel,  ductility  is  the  distortion  or  strain  a  body  undergoes  in 
being  ruptured. 

Malleability:  Some  kinds  of  matter,  metals  in  particular,  can  be 
hammered  or  rolled  into  thin  sheets.  This  property  is  called  malleability. 

Hardness  is  the  ability  to  withstand  abrasion,  or  resist  penetration. 

Crystallization :  Some  substances  in  changing  from  a  liquid  to  a  solid 
form,  separate  not  as  a  continuous  compact  mass  but  as  bodies  having  a 
definite  shape  and  color,  called  crystals.  That  crystals  may  form,  it  is 
necessary  that  the  molecules  be  free  to  arrange  themselves  in  a  definite 
order.  This  condition  is  secured  when  a  substance  is  in  solution  or  in  a 
molten  state.  In  steel  manufacture  this  property  is  of  great  importance. 

Diffusion  is  most  characteristic  of  liquids  and  gases.  It  is  the  property 
that  causes  two  fluids  in  contact  to  intermingle.  Liquids  diffuse  slowly, 
but  gases  much  more  rapidly. 

Effusion  is  the  term  applied  to  that  property  of  gases  which  causes 
them  to  pass  through  porous  solids.  The  rates  of  effusion  of  different  gases 
is  inversely  proportioned  to  the  square  roots  of  their  relative  weights. 

Absorption:  Many  porous  bodies,  like  coke,  charcoal,  platinum 
sponge,  etc.,  are  capable  of  absorbing  large  quantities  of  gases.  Thus, 
one  cubic  centimeter  of  charcoal  is  capable  of  absorbing  from  thirty  to 
thirty-five  times  its  own  volume  of  carbon  dioxide.  Gases  are  condensed 
on  the  surface  of  all  solids,  and  porous  bodies  offer  a  large  surface  for  con- 
densation. 

SECTION   III. 

ENERGY,    HEAT   AND   TEMPERATURE,    AND  THE   ETHER. 

Energy :  Physics  and  Chemistry,  however,  have  to  do  with  more  than 
matter.  The  senses  also  reveal  the  presence  of  a  second  factor  in  nature, 
called  energy.  Like  matter,  energy  is  a  fundamental  that  cannot  be 
satisfactorily  defined.  It  is  not  a  thing.  It  is  that  which  gives  a  body 
the  ability  to  move  against  a  resistance;  that  is,  the  ability  to  do  work. 


ENERGY  AND  HEAT 


Thus,  a  body  may  possess  energy  and  still  neither  move  nor  do  any  work. 
Like  matter,  energy  is  conserved.  It  may  be  changed  from  one  form  to 
another  or  be  transferred  from  one  point  to  another,  but  the  total  energy 
of  the  Universe  remains  constant.  This  fact  is  known  as  the  Law  of  Con- 
servation of  Energy. 

Kinds  of  Energy:  There  are  two  kinds  of  energy;  namely,  potential 
or  stored  up  energy,  sometimes  called  energy  of  position,  and  kinetic  energy, 
or  the  energy  possessed  by  a  body  by  virtue  of  its  motion.  Thus,  a  weight 
on  the  top  of  a  building  possesses  potential  energy  with  respect  to  the 
ground  by  virtue  of  its  position;  if  it  is  permitted  to  fall,  its  energy  then 
becomes  kinetic.  Energy  is  measured  in  terms  of  the  work  which  it  is 
capable  of  doing. 

Heat  and  Temperature:  One  form  of  energy  is  heat.  Heat  must 
not  be  confused  with  temperature.  The  latter  measures  one  of  the  effects 
of  the  former.  The  difference  may  be  illustrated  thus: — Let  it  be  supposed 
that  two  portions  of  natural  gas,  each  of  a  cubic  foot,  are  burned  completely, 
so  that  the  heat  liberated  is  entirely  absorbed  by  two  bodies  of  water 
initially  at  the  same  temperature,  the  volumes  of  which  are  a  quart  and 
a  gallon,  respectively.  It  is  evident  from  common  experience  that  the 
temperature  of  the  smaller  portion  of  water  will  be  raised  the  higher,  though 
the  quantity  of  heat  imparted  to  each  is  precisely  the  same. 

Effects  of  Heat :  Heat  produces  marked  effects  on  matter.  All  matter 
expands  by  the  application  of  heat  alone,  though  there  are  many  apparent 
exceptions.  The  volume  of  a  gas  varies  directly  as  the  absolute  temper= 
ature,  other  conditions  remaining  constant.  Change  of  state  may  be 
caused  by  heat.  Thus,  glass  or  iron,  dense  solids  at  ordinary  temperatures, 
readily  assume  the  fluid  state  on  being  heated  above  their  fusion  point. 
According  to  the  kinetic  theory  of  heat,  the  molecules  of  matter  always 
have  a  certain  amount  of  independent  motion,  and  the  effect  of  adding 
heat  is  to  increase  the  energy  of  this  motion,  the  molecules  being  thereby 
forced  farther  and  farther  apart.  This  forcing  apart  of  the  molecules 
accounts  for  the  change  of  state  as  well  as  the  expansion  of  bodies  on  being 
heated. 

Temperature  is  determined  by  measuring  the  expansion  it  produces  in 
a  volume  of  mercury  enclosed  in  a  small  glass  tube,  called  a  thermometer. 
The  length  of  the  tube  is  marked  off  into  small  divisions,  which  constitutes 
the  scale  of  the  thermometer.  There  are  four  thermometer  scales  in 
common  use;  the  Centigrade,  Fahrenheit,  Reaumur  and  Absolute.  The 
difference  among  them  consists  of  the  number  of  divisions  between  the 
freezing  point  and  the  boiling  point  of  water,  and  the  numbers  applied  to 
these  divisions. 

The  Centigrade  is  the  thermometer  employed  in  all  scientific  work. 
In  it  the  freezing  point  is  marked  zero  and  the  boiling  point  100°.  The  only 


ENERGY  AND  HEAT 


difference  between  this  scale  and  the  Absolute  is  that,  in  the  latter,^  the 
zero  point  is  273°  below  the  Centigrade  zero. 

In  the  Fahrenheit  thermometer,  the  space  between  the  freezing  and  the 
boiling  points  is  divided  into  180  equal  parts,  and  zero  is  32  of  these  parts 
below  the  freezing  point  of  water.  The  boiling  point,  therefore,  is  212°. 


In  the  Reaumur  scale,  the 
freezing  point  is  marked  zero 
and  the  boiling  point  80°.  For 
high  temperatures,  instruments 
called  pyrometers  are  used. 

These  relations  of  the 
various  scales  are  shown  in  the 
accompanying  diagram:  From 
this  diagram  the  following  for- 
mulas are  readily  developed: 

Temp.  A=Temp.  C+273. 
Temp.  C=Temp.  A— 273. 
Temp.    F=Temp.   %C+32. 
Temp.  C=Temp.  (F— 32°)%. 


Boiling  Point 


Ciooc 


F212« 


A373°         fop" 


of  Water 

Degrees         ° 
Intervening;      , 

1 

1 

B 

| 

ft 

freezing  Point      , 

0°        , 

32°     > 

273°  , 

0° 

of  Water 

0° 

O5 

FIQ.  1.  Diagram  showing  relations  of  the 
various  thermometer  scales. 


Measurement  of  Heat:  Heat  is  measured  in  calories.  A  calorie  (cal.) 
is  the  heat  required  to  raise  the  temperature  of  one  gram  of  water  one 
degree  centigrade.  In  practice  the  large  calorie  (Cal.)  is  employed.  It 
is  the  amount  of  heat  required  to  raise  one  kilogram  of  water  through 
one  degree  centigrade.  The  corresponding  unit  in  the  English  system  is 
the  B.  t.  u.  (British  thermal  unit),  which  is  the  heat  required  to  raise 
the  temperature  of  one  pound  of  water  one  degree  Fahrenheit.  These  units 
may  be  converted  from  one  to  the  other  by  use  of  the  following  factors: 

1  Calorie=3.968  B.  t.  u.  or 
1  B.  t.  u.=  .252  Cal. 

The  Ether:  A  third  factor  composing  the  Universe  is  the  Ether. 
Little  is  known  about  it  except  that  it  fills  all  space,  permeates  all  matter 
and  transmits  light,  heat,  and  electric  waves.  Its  properties  are  very 
difficult  to  analyze,  because  the  senses  are  not  directly  affected  by  it.  Its 
presence  was  first  suspected  through  the  study  of  the  transmission  of  light. 
By  comparatively  simple  experiments,  it  was  shown  as  early  as  1802  that 
light  is  transmitted  by  a  wave  motion,  and  since  light  is  transmitted  through 
a  vacuum,  something  other  than  matter  must  act  as  the  medium.  The 
same  conclusion  is  arrived  at  by  a  study  of  heat  radiation.  The  develop- 
ment of  wireless  telegraphy  was  based  on  this  supposition,  and  its  success 
is  further  evidence  of  the  existence  of  the  Ether. 


CHANGES  IN  MATTER 


SECTION    IV. 

CHANGES  IN   MATTER. 

Physical  and  Chemical  Changes:  Matter  is  constantly  undergoing 
changes.  A  close  observer  soon  discerns  that  these  changes  are  of  two 
kinds, — namely,  one  in  which  the  nature  and  composition  of  the  matter 
undergoing  the  change  remains  the  same,  called  a  physical  change,  and 
another  in  which  the  nature  and  composition  are  affected,  called  achemical 
change.  The  bending  of  a  stick,  the  freezing  of  water,  the  fusion  of  steel 
are  examples  of  the  former,  while  the  burning  of  coal  is  a  common  example 
of  the  second.  In  many  physical  changes  and  in  all  chemical  changes  heat 
is  involved, — being  either  absorbed  or  liberated.  Chemical  changes  that 
liberate  heat  furnish  a  source  of  energy — •  chemical  energy. 

The  Make=up  of  Material  Bodies:  In  considering  the  make-up  of 
the  various  bodies  of  matter,  it  is  necessary  to  distinguish  between  mere 
mixtures  and  more  closely  combined  substances.  A  mechanical  mixture 
is  a  mixture  of  two  or  more  substances,  which  is  not  homogeneous  and  the 
components  of  which  can  be  separated  by  mechanical  means.  Such  mix- 
tures are  made  up  of  molecules  of  different  kinds.  A  chemical  compound 
is  homogeneous  throughout  its  mass,  and  its  components  cannot  be  separat- 
ed by  mechanical  means,  that  is,  its  molecules  are  all  of  the  same  kind.  The 
components  of  any  given  chemical  compound  are  always  in  the  same  pro- 
portions for  that  compound.  This  fact  distinguishes  compounds  from 
alloys  and  solutions  which,  though  they  are  practically  homogeneous  and 
sometimes  are  practically  impossible  of  separation  by  mechanical  means, 
are  never  constant  in  composition.  An  alloy  is  a  solid  solution  of  one 
metal  in  another. 

Kinds  of  Chemical  Compounds:  A  close  study  of  a  great  number 
of  chemical  compounds  will  show  that  all  substances  fall  into  four  classes; 
namely,  acids,  bases,  salts  and  non-electrolytes. 

Acids  are  characterized  by  the  fact  that  they  all  have  a  sour  taste 
when  in  water  solution  and  change  the  color  of  certain  chemicals,  called 
indicators.  One  of  the  most  common  of  these  indicators  is  litmus,  of 
which  there  are  two  colors,  a  blue  and  a  red.  Acids  change  the  color  of 
blue  litumus  to  red.  Vinegar  is  chiefly  a  dilute  solution  of  acetic  acid. 

Bases  have  the  power  of  neutralizing  acids,  and  may  be  looked  upon 
as  their  opposites.  Examples  are  quick  lime,  lye,  etc.  Bases  change  the 
color  of  red  or  neutral  litmus  to  blue. 

A  Salt  is  the  product  formed  when  an  acid  is  neutralized  by  a  base. 
Common  table  salt,  made  by  neutralizing  hydrochloric  acid  with  sodium 
carbonate,  is  an  example.  As  a  rule  acids,  bases,  and  salts  are  electrolytes, 
that  is,  their  water  solutions  will  conduct  the  electric  current. 

Non  Electrolytes :  There  are  some  compounds  that  do  not  resemble 
either  acids  or  bases,  nor  can  they  be  classed  as  salts.  They  are  char- 
acterized by  the  fact  that  their  water  solutions  will  not  conduct  the  electric 
current,  so  are  termed  non-electrolytes.  Benzene,  methane  and  distilled 
water  are  examples. 


CHANGES  IN  MATTER 


Chemical  Elements:  Notwithstanding  the  fact  that  chemical  com- 
pounds are  homogeneous  and  cannot  be  separated  by  mechanical  means, 
they  are  readily  divided  into  simpler  substances  by  chemical  processes, 
These  simpler  substances  are  called  elements,  and  each  and  every  chemical 
compound  is  composed  of  two  or  more  chemical  elements.  While  the 
number  of  chemical  compounds  is  almost  unlimited,  there  are  compara- 
tively few  elements.  In  1918,  the  discovery  of  84  elements  had  been 
reported.  The  total  number  lies  between  92  and  97.  Of  these,  twelve 
compose  about  99  per  cent,  of  the  earth's  crust.  It  has  been  estimated 
that  the  solid  crust  of  the  earth  is  made  up  approximately  as  follows: 

Oxygen 49.85%    Calcium 3. 18%    Hydrogen 97% 

Silicon 26.03%     Sodium 2.33%     Titanium 41% 

Aluminum 7.28%     Potassium 2.33%    Chlorine 20% 

Iron 4.12%    Magnesium 2.11%     Carbon 19% 


TOTAL  99.00% 

Classification  of  Chemical  Elements:  A  study  of  the  elements 
reveals  the  fact  that  there  are  two  great  classes;  namely,  those  that  combine 
with  oxygen  and  hydrogen  to  form  bases,  and  those  that  combine  with  oxygen 
and  hydrogen,  or  hydrogen  alone,  to  form  acids.  The  former  are  sometimes 
called  metals  and  the  latter  non=metals,  or  metalloids.  The  line  of 
division  is  not  a  sharp  one.  Some  elements  form  both  acids  and  bases, 
but  the  tendency  is  more  pronounced  in  the  one  direction  than  in  the  other. 
Furthermore,  like  plants  or  animals,  these  two  divisions  may  be  sub-divided 
into  families  or  groups,  the  members  of  which  possess  similar  properties. 
These  divisions  and  groups  are  shown  in  a  subjoined  table. 

Symbols:  For  convenience  and  brevity,  each  element  is  represented 
by  a  symbol.  These  symbols  are  composed  of  the  first  letter,  capitalized, 
of  the  English  or  Latin  names  of  the  elements,  combined,  where  necessary 
as  a  distinguishing  mark,  with  some  succeeding  letter.  Thus,  C=carbon, 
Ca=calcium,  Cd=cadmium,  F=fluorine,  Fe=ferrum  (iron),  etc. 

Fundamental  Laws  of  Chemical  Changes:  Now,  where  the  elements 
combine  to  form  a  compound  they  always  do  so  in  definite  proportions 
by  weight.  Thus,  fifty-six  parts  by  weight  of  iron  will  combine  with 
sixteen  parts  by  weight  of  oxygen,  or  fourteen  parts  by  weight  of  nitrogen 
with  sixteen  parts  by  weight  of  oxygen.  This  fact  is  known  as  the  Law  of 
Definite  Proportions,  and  the  definite  weights  are  called  combining  weights. 
Further  investigation  along  this  line  shows  that  some  pairs  of  elements  form 
more  than  one  compound  and  that  the  combining  weights  of  the  elements 
in  these  different  compounds  are  simple  multiples  of  each  other.  Concisely 
stated,  the  law  is  this:  Whenever  two  elements  unite  to  form  more  than 
one  compound,  if  we  consider  a  fixed  weight  of  the  one,  the  weights  of 
the  other  which  combine  with  it  are  integral  multiples  of  one 
another.  This  fact  is  known  as  the  Law  of  Multiple  Proportions,  or 
Dalton's  second  law.  The  following  compounds  formed  by  the  two 


10  ATOMS 


elements  nitrogen  and  oxygen  are  well  known  examples : 

COMPOUND                                    PARTS  BY  WEIGHT  PARTS  BY  WEIGHT 

OF  NITROGEN  OF  OXYGEN 

Nitrous  Oxide 28  16 

Nitric  Oxide 28  32 

Nitrogen  Trioxide 28  48 

Nitrogen  Peroxide 28  64 

Nitrogen  Pentoxide 28  80 

SECTION   V. 

THE   ATOMIC  AND  ELECTRON  THEORIES. 

Atoms:  Upon  the  facts  just  stated  in  the  preceding  section,  the 
English  chemist  Dalton  founded  a  very  important  hypothesis,  now  known 
as  the  atomic  theory.  In  order  to  explain  the  laws  stated  above,  reasoning 
led  to  the  following  assumptions: 

1st:     The  molecules  of  matter  are  themselves  made  up  of  small  particles. 

2d:  These  particles  possess  the  power  of  attracting  other  particles  or 
otherwise  attaching  themselves  to  them. 

3d:     These  particles  do  not  subdivide  in  taking  part  in  chemical  changes. 

These  particles  are  called  atoms.  All  the  atoms  of  the  same  element 
have  the  same  mass  or  weight,  the  same  form,  and  the  same  combining 
power,  while  atoms  of  different  elements  differ  in  one  or  more  of  these 
respects. 

Atomic  Weights:  The  atom  is  so  small  that  it  is  useless  to  hope  that 
its  mass  or  weight  will  ever  be  determined  absolutely.  However,  the 
weight  of  one  atom  of  an  element  must  be  proportional  to  the  combining 
weight  of  that  element.  Since  the  combining  mass  or  weight  of  hydrogen 
is  the  least  of  all  the  otjier  elements,  it  is  assumed  that  its  atom  is  the 
lightest.  Therefore,  the  atomic  weight  of  hydrogen  was  made  one  by 
Dalton  and  the  atomic  weight  of  the  other  elements  multiples  of  it.  However, 
since  hydrogen  forms  with  other  elements  comparatively  few  compounds 
that  can  be  used  for  atomic  weight  determinations  and  oxygen  more  than 
any  other  element,  it  was  decided  later  to  make  the  latter  element  the 
standard.  Accordingly,  the  atomic  weight  of  oxygen  is  made  16,  and  the 
atomic  weights  of  other  elements  are  compared  with  it  as  a  standard,thus 
making  hydrogen  1.008.  This  system'  of  comparative  weights  is  known  as 
the  international  table  of  atomic  weights. 

Valence :  Concerning  the  attractive  power  of  the  atoms  of  the  various 
elements,  it  may  be  pointed  out  that  the  law  of  multiple  proportions  indicates 
that  the  atom  of  an  element  may  combine  with  one  or  more  atoms  of  another 
element  in  forming  compounds  with  it.  Here,  again,  hydrogen  is  used  as 
a  standard,  for  since  its  combining  weight  is  the  least  of  all  the  other 
elements,  it  is  assumed  that  the  holding  power  of  its  atoms  must  also 
be  the  least.  Therefore,  the  valency  of  an  atom  is  properly  denned 
as  the  number  of  hydrogen  atoms  it  is  capable  of  combining  with 
or  replacing.  The  valencies  of  the  atoms  of  the  elements  are  by  no 
means  fixed  quantities,  but  vary — in  some  cases  from  one  to  seven. 


ELEMENTS 


11 


The  following  table  is  intended  to  furnish  a  complete  list  of  the  elements, 
with  their  symbols  and  atomic  weights,  and  to  show,  also,  the  classification 
and  valencies  of  the  more  common  ones.  Very  rare  elements  are  placed 
in  a  separate  list.  Elements  that  ordinarily  are  both  acid  and  basic 
are  marked  with  an  *,  and  those  important  in  the  manufacture  of  steel 
are  printed  in  Italics. 

Table  I — The  Chemical  Elements. 

Showing  Physical  Constants  of  the  More  Common  Ones. 


0 

Group 

Name 

I 

£ 

1920 

Atomic 
Weight 

Valence 

Specific 
Gravity 

Melting 
Point 

Boiling 
Point 

0=16 

Water 

Air 

°C 

°C 

BASE  FORMING 

Potassium 
Calcium.  .  . 

Magnesium 
Silver  
Aluminum 

Lead  
Chromium 

Manganese 
Iron  

Palladium. 
Gold 

Lithium  
Potassium  
Sodium 

Li 

K 

Na 

Ca 
Ba 
Gl 

Sr 

Mg 
Zn 
Cd 

Ag 
Cu 
Hg 

Al 
Ga 
Tl 
Sc 

Pb 

Sn 

Cr 

Mo 

W 

Mn 

Fe 
Co 

Ni 

Pd 
Ru 
Rh 

Pt 
Au 

6.94 
39.1 
23.0 

40.07 
137.37 
9.1 
87.63 

24.32 
65.37 
112.40 

107.88 
63.57 
200.60 

27.1 
70.1 
204.0 
44.1 

207.2 
118.7 

52.0 
96.0 
184.0 

54.93 

55.84 
58.97 
58.68 

106.7 
101.7 
102.9 

195.2 
197.2 

I 

/ 
/ 

// 
II 
II 
II 

// 
II 
II 

I 
I-II 
I-II 

III 

.59 

.87 
.97 

1.58 
3.8 
1.85 
2.5 

1.7 
7.1 
8.6 

10.5 
8.9 
13.60 

2.58 
5.95 
11.85 

11.3 
7—7.3 

6.9 
8.8 
18.8 

7.4 

7.78 
8.7 
8.7 

11.8 
8.6 
12.1 

21.5 
19.3 

186 
62.5 
97.6 

810 
850 
960 
900 

650 
419 
321 

961 
1083 
—  38.8 

657 
30 
302 
1200 

327 
232 

1505 
2500 
1700 

1225 

1520 
1610 

1450 

1550 
1950 
1940 

1753 
1062 

1400 

667 
742 

Calcium  

Barium  
Glucinum  

950 

Strontium 

Magnesium  
Zinc  .  .  . 

1120 
918 

778 

1955 
2100 
357 

1800 

Cadmium  
Silver 

Copper 

Mercury  
*  Aluminum. 

Gallium  (rare)  .  .  . 
Thallium    "      ... 
Scandium  "     ... 

*Lead  
*Tin  

Chromium  . 

II-IV 
II-IV 

II-III-VI 
II-IV 

II-III 
II 
II 

IV 

I-III 

1525 
1525 

2200 

*  Molybdenum  .  .    . 

*Tungsten  
*  Manganese  

Iron  
Cobalt  

1900 
2450 

Nickel  

2530 

*Palladium  
Ruthenium  (rare) 
Rhodium  (rare)  .  . 

*Platinum 

*Gold  

12 


ELEMENTS 


Table  I— The  Chemical  Elements— Continued. 


0 

Group 

Name 

I 

1920 
Atomic 
Weight 

Valence 

Specific 
Gravity 

Melting 
Point 

Boiling 
Point 

0=16 

Water 

Air 

°C 

°C 

Chlorine  .  . 

Fluorine  

F 

19.0 

j 

1.26 

—  223 

—  187 

Chlorine..  

Cl 

35.46 

I 

2.49 

—  102 

—  37.6 

Bromine  

Br 

79.92 

I 

3.1 

—  7.3 

59 

Iodine  

I 

126.92 

I 

4.9 

114 

184 

Sulphur.  .  . 

Sulphur  

5  ' 

32.06 

II-IV-VI 

2.0 

116.5 

444.6 

Selenium  (rare)  .  . 

Se 

79.20 

4.3 

218.5 

690 

Tellurium    " 

Te 

127.50 

6.2 

451 

1390 

p 

^H 

Carbon  .  .  . 

Carbon  

C 

12.0 

IV 

1.7-3.5 

Infusible 

3500 

§ 

Silicon 

Si 

28.3 

IV 

2.49 

1420 

3500 

^-4 

Boron.  . 

B 

10.9 

III 

2.40 

2250 

3500 

C 

Titanium  

Ti 

48.10 

IV 

3.54 

1795 

g 

Nitrogen  .  . 

Nitrogen  

N 

14.01 

I  to  V 

.96 

—  213 

—  196 

o 

Phosphorus  

P 

31.04 

III-V 

1.8 

44.1 

290 

<! 

*Arsenic  

As 

74.96 

III-V 

5.7 

185 

449.5 

*  Antimony  

Sb 

120.20 

III-V 

6.6 

630 

1460 

*Bismuth  

Bi 

208.0 

III-V 

9.7 

269 

1485 

^Vanadium  

V 

51.0 

III-V 

5.9 

1680 

Oxygen 

0 

16.0 

II 

1.10 

—  218 

—  182 

(15.97) 

Hydrogen 

H 

1.008 

I 

.07 

—  259 

—  252 

(1.) 

Name 

51  Argon 

52  Caesium 

53  Cerium 

54  Columbium. . . 

55  Dysprosium... 

56  Erbium 

57  Europium 

58  Gadolinium... 

59  Germanium. . . 

60  Helium 

61  Holmium 

62  Indium 

63  Iridium 

64  Krypton 

65  Lanthanum . . . 

66  Lutecium 

67  Neodymium.  . 


Very  Rare  Elements. 

Atomic 
Symbol  Weight  Name 

A  39.9  68  Neon 

Cs  132.81  69  Niton 

Ce  140.25  70  Osmium 

Cb  93.1  71  Praseodymium 

Dy  162.5  72  Polonium 

Er  167.7  73  Radium 

Eu  152.0  74  Rubidium 

Gd  157.3  75  Samarium 

Ge  72.50  76  Tantalum 

He  4.0  77  Terbium 

Ho  163.5  78  Thorium 

In  114.8  79  Thulium 

Ir  193.1  80  Uranium 

Kr  82.92  81  Xenon 

La  139.0  82  Ytterbium 

Lu  175.0  83  Yttrium 

Nd  144.30  84  Zirconium.. 


Atomic 
Symbol  Weight 


Ne 

Nt 

Os 

Pr 

Po 

Ra 

Rb 

Sa 

Ta 

Tb 

Th 

Tm 

U 

Xe 

Yb 

Yt 

Zr 


20.2 
222.4 
190.9 
140.9 
210.0 
226.0 

85.45 
150.4 
181.5 
159.2 
232.15 
168.5 
238.2 
130.2 
173.5 

89.33 

90.6 


REACTIONS  13 


Electrons:  Until  1900  all  the  elements  had  resisted  all  efforts  to 
break  them  up  into  simpler  substances,  and  atoms  were  considered  to  be 
the  smallest  divisions  of  matter.  With  the  discovery  of  radium  and  other 
radio-active  substances,  however,  a  new  field  for  investigation  was  opened, 
and  subsequent  discoveries  indicate  that  the  atom  is  divisible.  These  very 
small  particles  are  called  electrons.  It  is  thought  that  electrons,  in  some 
intimate  relation  to  the  Ether,  are  the  fundamental  particles  of  which  all 
matter  is  composed. 

SECTION  VI. 
CHEMICAL  FORMULA  AND   REACTIONS. 

Chemical  Formulas  of  Compounds:  The  method  of  representing  the 
elements  by  symbols,  together  with  the  system  of  atomic  weights,  affords 
a  convenient  and  concise  method  of  representing  chemical  compounds,  or 
to  be  more  explicit,  the  molecules  of  chemical  compounds.  Thus,  by 
analysis,  water  is  found  to  be  composed  of  hydrogen  and  oxygen  in  the 
proportion  of  eight  parts  of  oxj^gen  to  one  part  of  hydrogen  by  weight. 
These  facts  are  completely  expressed  by  the  formula  H2O,  which  indicates 
a  molecule  of  a  compound  composed  of  two  atoms  of  hydrogen  and  one 
atom  of  oxygen,  or,  since  the  atomic  weight  of  hydrogen  is  1  and  of 
oxygen,  16,  2  parts  of  hydrogen  to  16  parts  of  oxygen  (1  to  8).  Likewise, 
the  formula  Fe2O3  represents  a  compound,  the  molecule  of  which  is  made 
up  of  111.68  parts  of  iron  to  48  parts  of  oxygen. 

Molecules  of  Elements:  In  studying  chemical  changes  in  which 
elements  are  set  free,  it  is  found  that  they  are  much  more  active  at  the 
instant  of  their  liberation  than  afterwards,  and  are,  therefore,  said  to  be 
in  the  nascent  state  at  that  instant.  This  fact  leads  to  the  belief  that 
the  instant  an  element  is  set  free  from  its  compounds  it  exists  in  the  atomic 
condition,  but  if  there  is  nothing  else  present  with  which  the  atoms  can 
combine,  they  combine  with  each  other  to  form  molecules  of  the  element. 
This  idea  cannot  be  proven  in  the  case  of  solids,  but  its  correctness  is  easily 
shown  in  the  case  of  gases.  From  many  facts,  Avogadro  was  able  to  show 
that  equal  volumes  of  all  gases,  under  the  same  conditions  of  temper- 
ature and  pressure,  contain  the  same  number  of  molecules.  Hence, 
the  molecular  weight  in  grams  of  all  gases  give  a  constant  volume  of  22.32 
liters,  called  the  gram-molecular  volume.  Now,  the  weight  of  22.32  liters 
of  oxygen=32  gms.,  of  hydrogen,  2  gms.,  of  nitrogen,  28  gms.  Dividing 
these  weights  by  the  respective  atomic  weights  of  the  elements,  the  quotient 
is  2  in  each  case.  Hence,  the  molecules  of  these  elements  contain  two  atoms 
each,  and  the  correct  formulas  for  these  elements  are  O2,  H2  and  N2, 
respectively. 

Chemical  Equations:  This  system  of  symbols  and  weights  also 
simplifies  the  representation  of  chemical  changes.  Suppose  it  is  desired  to 
represent  the  chemical  change  that  takes  place  when  a  common  substance, 
like  coal  for  instance,  burns.  Coal  is  largely  made  up  of  carbon;  the  element 
which  combines  with  it  is  oxygen  in  the  air;  an  invisible  gas,  CO2,  is 


14 


REACTIONS 


formed  and  diffuses  into   the  air.     This  change,  spoken  of  as  a  reaction, 
is  represented  in  the  form  of  an  equation;  thus,  C+O=COs. 

Balancing  Reactions:  Since  matter  is  conserved,  there  must  be  as 
many  atoms  on  one  side  of  the  equation  as  on  the  other.  This  is  shown  by 
placing  a  2  before  O  on  the  left  side  of  the  equation,  thus,  C+2O=CO2. 
This  process  is  called  balancing.  Thus,  reactions  tell  not  only  the  names 
of  the  reacting  substances  and  of  the  products  formed,  but  also  give  the 
proportions  by  weight,  and  in  the  case  of  gases,  volume  relations  as  well. 

Radicals:  In  .the  molecules  of  many  chemical  compounds,  certain 
groups  of  atoms  appear  to  be  more  closely  bound  together  than  others  in 
the  same  molecule.  In  these  groups  the  atoms  composing  them  appear  to 
bear  a  fixed  relation  to  each  other,  which  remains  unchanged  during  a 
chemical  reaction.  Thus,  in  many  wet  reactions  in  which  H^SO^  is 
employed  as  a  reagent,  the  sulphur  and  oxygen  do  not  separate  but 
remain  closely  combined,  as  illustrated  in  the  reaction  that  takes  place 
between  this  acid  and  barium  chloride: 

H2  (S04)+Ba  Cl2=Ba  (SO4)+2  HC1 
Such  groups  of  atoms  are  called  radicals. 

Ions  and  Electrolysis:  In  electrolytes  these  radicals  are  readily 
identified  as  ions.  From  a  study  of  the  effect  of  dissolved  electrolytes  on 
the  boiling  and  freezing  points  of  the  water  in  which  they  are  dissolved, 
and  on  their  osmotic  pressures,  evidence  is  obtained  to  show  that  each  of 
the  dissolved  molecules  breaks  up  or  dissociates  into  two  parts. 

The  following  simple  experi- 
ment may  be  employed  to  throw 
additional  light  upon  this  sub- 
ject. Into  the  U-tube  of  Fig.  2 
is  placed  a  solution  of  sodium 
sulphate  and  some  neutral 
litmus,  into  which  is  immersed 
two  small  platinum  rods  to  act 
as  electrodes  for  an  electric 
current,  as  shown  in  the  figure. 
Upon  closing  the  circuit,  bubbles 
of  hydrogen  are  given  off  at  the 
cathode  and  bubbles  of  oxygen 
at  the  anode,  while  the  solution 
about  the  cathode  becomes  deep 
blue  in  color,  showing  it  is  basic, 
and  that  about  the  anode  be- 
comes red,  showing  it  to  be 
acid.  These  facts  are  explained 
by  assuming  that  the  molecules 


Pi  a.  2.  Showing  decomposition  of  water  and 
formation  of  sodium  hydroxide  and  sulphuric 
acid  from  sodium  sulphate  by  electrolysis. 


REACTIONS  15 


of     dissolved        Na2SO4      dissociate     into     parts,     called     ions.       This 

+        + 
dissociation   is  indicated    thus:    Na2SO4=Na-fNa+SO4.      The     sodium 

+ 
ions,  Na,  carrying    a    positive    charge    of  electricity,   are   propelled    by 

the  current  toward  the  cathode,  while  the  negatively  charged  sulphions, 
SO4,  go  to  the  anode.      Here  they  give   up   their    charges   and  become 
chemically  active,  decomposing  the  water  thus: 
2Na+2H2O=2NaOH+H2 


This  experiment  is  but  one  example  of  electrolysis.  Any  inorganic  acid, 
base  or  salt  may  be  substituted  for  the  sodium  sulphate;  and  any  conductor 
of  electricity,  such  as  iron,  may  be  used  instead  of  platinum.  It  is  to  be 
noted,  however,  that  if  iron  had  been  used  in  this  experiment,  the  anode 
would  have  been  corroded  away  by  the  acid  radical;  thus,  Fe+SO4= 
FeSO4.  Electrolysis  has  been  advanced  to  explain  the  corrosion  of  iron. 

Dry  and  Wet  Chemistry  :  Chemical  changes  take  place  under  constant 
conditions.  Substances  that  will  react  in  one  way  under  one  set  of  con- 
ditions  will  not  react,  or  react  in  an  entirely  different  way,  under  another 
set  of  conditions.  Some  substances  react  simply  by  contact,  as  quick  lime 
and  water.  Many  reactions  will  take  place  only  in  a  water  solution,  while 
many  other  substances,  being  insoluble  in  water,  must  be  heated  almost 
to  their  point  of  fusion  before  they  react.  A  study  of  reactions  between 
substances  in  solution  is  called  "wet  chemistry"  while  the  study  of  reactions 
brought  about  by  heat  is  termed  ''dry  chemistry."  However,  under  the 
same  conditions,  the  same  substances  will  always  produce  the  same  results. 
This  fact  is  known  as  the  law  of  constancy  of  nature. 

Acids,  Bases  and  Salts  of  Dry  Chemistry:  Most  substances  dealt 
with  in  wet  chemistry  lose  water  when  heated.  This  statement  is  par- 
ticularly true  of  inorganic  acids,  bases  and  salts.  Thus,  in  the  case  of 
acids  and  bases,  heat  breaks  up  these  compounds  into  water  and  oxides, 
called  anhydrides.  Acids  give  acid  anhydrides,  and  bases,  basic 
anhydrides.  These  anhydrides  constitute  the  acids  and  bases  of  dry 
chemistry.  They  have  the  same  power  of  neutralization  that  their 
corresponding  wet  compounds  possess,  and  form  neutral  compounds  to  which 
the  term  slag  is  applied  instead  of  salt.  Many  salts,  in  crystallizing  from 
aqueous  solutions,  unite  with,  or  better,  take  up  a  definite  amount  of  water, 
which  does  not  go  to  form  a  new  compound,  but  to  form  crystals,  and  is 
called,  therefore,  water  of  crystallization.  This  water  is  held  very  loosely 
by  the  molecule  and  is  readily  given  up  by  it.  In  some  crystals,  like  those 
of  washing  soda,  for  example,  this  tendency  is  so  pronounced  that  they  give 
up  their  water  of  crystallization  to  the  air,  if  its  humidity  is  low.  Such 
substances  are  said  to  be  efflorescent.  On  the  other  hand,  many  dry 
substances  absorb  moisture  from  the  air  and  are,  therefore,  said  to  be 


16 


REACTIONS 


hygroscopic.  A  few  substances  will  absorb  enough  water  from  a  very 
moist  air  to  become  wet  and  actually  go  into  solution  in  the  water  they 
absorb.  These  substances  are  said  to  be  deliquescent.  The  following 
reactions  will  serve  to  illustrate  these  facts  in  so  far  as  they  involve  chemical 
changes: 

H2SiO8-fheat=H2O+SiO2 
Metasilicic  Acid    Water      Silica,  or  silicic  anhydride 

Mg  (OH)2+heat=H2O+MgO 
Magnesium  hydroxide          Magnesia — a  basic  anhydride 

Na2SO4.10H2O+heat=10H2O+Na2SO4 
Glauber  Salt  Sodium  Sulphate 

(Crystallized)  (Dry  Powder) 

In  this  connection  a  study  of  the  following  table  will  also  prove  helpful. 

Table  2.     Acids,  Bases  and  their  Anhydrides  with  Salts 
Resulting  from  Neutralization. 


Salt  With 

Name  of  Compound 

Formula  of 
Compound 

Formula  of 
Anhydride 

Univalent  Base 

Divalent  Base 

Trivalent  Base 

Sodium  hydroxide 

NaOH 

Na->0 

Calcium  hydroxide 

Ca(OH)2 

Cat) 

Ferric  hydroxide 

Fe(OH)3 

Fe203 

Sulphuric  Acid 

H2S04orH20-S03 

S03 

NaoO-SOaor 

CaO-SOacr 

(Fe203).(S03)a 

Na2S04 

CaSOt 

orFe2  (BO*)  3 

Nitric  Acid 
Orthophosphoric  Acid 
Orthosilicic  Acid 

HN03or 
H-,0-No05 
H3P04or 
3H20-P.»05 
H4Si04~or 
2H20-Si02 

N205 
Si02 

Na.»0-N205or 
NaNOs 
3Na.>0-P-.05or 
Na3P04 
2Na.,0-SiO.>or 

CaO-N.,05or 
Ca(N03)o 
(CaO)»-P2Or, 
orCa:!(P04)2 
(CaO)  2-Si02 
orCa2Si04 

Fe203-(N205)s 

orFe(N03)3 

orFePOt  ° 
ofFe4(Si04)"3 

Kinds  of  Reactions :  As  already  indicated,  all  reactions  may  be  placed 
under  one  of  two  heads;  namely,  those  that  liberate  heat,  called 
exothermic,  and  those  that  absorb  heat,  called  endothermic.  A  more 
detailed  classification,  such  as  the  following,  is  sometimes  employed: 

1.  Direct  combination  (synthesis)— 2H+O=H2O  or  2H2+O2=2H2O. 

2.  Direct  decomposition  (analysis) — 2HgO=2Hg+O2. 

3.  Simple  replacement  or  substitution— 2H2O+2Na=2NaOH+H2. 

4.  Double  replacement  or  metathesis— BaCl2+H2SO4=BaSO4  +2HC1. 

/3  Fe+4O=Fe3O4. 
<„    ni       n,     ,-,    ~, 

(Fe  CI2+Cl=re  Cls. 

/Fe3O4+8H=3  Fe+4H2O. 
"\Fe  Cl3+H=Fe  C12+HC1. 
The  two  processes  of  oxidation  and  reduction  are  of  great  importance 
in  metallurgy.     They  have  a  triple  meaning.     Primarily,  oxidation  means 
the  taking  on  of  oxygen  by  an  element  or  compound,  and  reduction  means 
the  giving  up  of  oxygen.     In  the  case  of  elements  that  form  more  than  one 


5.     Oxidation — < 


6.     Reduction — < 


REACTIONS  17 


compound,  if  the  number  of  atoms  of  one  that  combines  with  a  fixed  number 
of  the  other  be  increased,  the  process  is  oxidation;  if  decreased,  reduction. 
In  metallurgy  an  element  in  the  metallic  state  is  said  to  be  reduced.  The 
two  processes  are  inseparable;  when  one  thing  is  reduced,  another  is 
oxidized.  In  metallurgical  operations  these  two  processes  are  of  paramount 
importance,  for  all  the  substances  reduced  constitute  the  metallic  product 
and  all  in  oxidized  form  make  up  the  slag. 

Some  Laws  Controlling  Chemical  Reactions:  In  writing  reactions 
considerable  knowledge  of  a  specific  character  is  essential.  Thus,  suppose 
it  is  required  to  write  the  reaction  that  represents  the  action  of  iron  brought 
in  contact  with  water.  First,  it  will  be  necessary  to  know  under  what 
conditions  the  substances  are  brought  together,  for  at  ordinary  temperatures 
no  reaction  will  take  place.  At  a  high  temperature,  a  reaction  takes  place, 
and  it  is  necessary  to  know  that  ferroso-ferric  oxide  and  hydrogen  are 
produced,  and  the  formulas  of  all  these  substances.  This  knowledge  can 
then  be  indicated  thus:  Fe+H2O=Fe3O4+H2.  Balancing  the  reaction, 
which  is  done  by  inspection  and  arithmetic,  is  the  next  step.  Finally, 
the  reaction  is  reversible,  for  if  instead  of  steam  over  hot  iron,  hydrogen 
be  passed  over  hot  iron  oxide,  iron  and  water  are  the  products.  The  reaction 
is,  therefore,  correctly  written  thus:  Fe3O4+4H2  =*=  3Fe+4H2O,  or  3Fe+ 
4H2O  =*=  Fe3O4+4H2.  Many  reversible  reactions,  under  conditions  which 
do  not  permit  the  products  to  escape  from  the  field  of  action,  do  not  pro- 
ceed to  completion,  but  reach  a  balanced  condition  after  a  time  and  seem 
to  stop,  though  as  a  matter  of  fact  they  are  progressing  in  one  direction  as 
rapidly  as  in  the  other,  hence  are  described  as  being  in  dynamic  equilibrium. 
In  practical  chemical  work  it  is  usually  desirable  to  have  reactions  go  to 
an  end.  As  an  aid  in  writing  reactions  the  following  laws  may  be  found  of 
value: 

A.  The  reaction  of  two  or  more  substances  will  go  to  an  end,  that  is, 
will  be  complete,  provided, 

1.  One  of  the  products  is  volatile  at  the  temperature  of  the  reaction. 

2.  One  of  the  products  is  insoluble  in  the  solvent  in  which  the  reaction 

takes  place. 

3.  One  of  the  products  is  a  non-electrolyte,  that  is,  does  not  ionize  in 

the  solvent. 

B.  The  speed  of  a  chemical  action  in  a  given  direction  may  be  increased 
by  effecting  a  greater  concentration  of  one  of  the  reacting  substances. 
This  is  a  simple,  non-mathematical  statement  of  the  law  of  mass  action. 

C.  Chemical  reactions  always  tend  to  proceed  in  the  direction  that 
will  liberate  the  most  heat,  and  without  the  addition  of  heat  from  an  external 
source  those  substances  that  have  the  greatest  heats  of  formation  will 
tend  to  form. 


18  CHEMICAL  NOMENCLATURE 

SECTION   VII. 

CHEMICAL   NOMENCLATURE. 

General  Principle:  A  brief  description  of  the  nomenclature  of 
chemical  compounds  will  be  found  of  great  assistance  to  those  not  familiar 
with  the  subject.  The  names  of  the  elements  first  discovered,  and,  there- 
fore, unfortunately,  the  more  common  ones,  are  not  based  on  any  principle; 
but  of  the  more  recently  discovered  elements  the  metals  have  received 
names  ending  in  um  orium,  and  the  metalloids,  in  n  or  ne.  Jn  the  naming 
of  compounds,  however,  the  old  names  have  been  discarded  and  new  ones 
substituted.  The  system  employed  in  assigning  these  new  names  is  this: 
The  name  of  a  compound  should  show  the  elements  of  which  it  is 
composed,  and  as  far  as  possible  their  relative  proportions. 

Terminology  of  Binary  Compounds:  The  simplest  compounds  are 
those  composed  of  only  two  elements.  The  names  of  all  such  compounds 
are  made  up  of  the  name  of  the  basic  element,  if  one  is  present,  succeeded 
by  the  name  of  the  acid  element,  which  ends  in  ide:  examples;  ferrous  (iron) 
sulphide,  FeS;  sodium  chloride,  NaCl;  calcium  oxide,  CaO. 

In  such  cases  as  iron  and  sulphur  where  the  same  two  elements  combine 
to  form  more  than  one  compound,  the  compounds,  when  two  in  number,  are 
distinguished  by  changing  the  ending  of  the  metallic  part  of  the  name  from 
ous  to  ic;  thus,  ferrous  sulphide,  FeS;  ferric  sulphide,  FeS2;  stannous 
chloride,  SnCl2;  stannic  chloride,  SnCl4.  Often,  the  prefixes  mono-,  di-,  tri-, 
tetra-,  pent-,  per  are  used,  especially  if  the  name  will  not  permit  the  ending 
ous  and  ic,  or  if  more  than  two  compounds  are  formed  by  the  same  two 
elements.  Carbon  dioxide,  CO2;  nitrous  oxide,  or  nitrogen  monoxide,  N2O; 
nitric  oxide  or  nitrogen  dioxide,  N2O2;  (NO);  nitrogen  trioxide,  N2Os; 
nitrogen  tetroxide  or  nitrogen  peroxide,  N2O4,;  nitrogen  pentoxide,  N2Os 
are  examples. 

Terminology  of  Ternary  Compounds:  The  names  of  compounds 
,that  contain  three  elements,  provided  they  are  not  derived  from  acids, 
may  end  in  ide,  also,  in  which  case  all  three  of  the  elements  appear  in  the 
name,  as  sodium  aluminum  fluoride,  (NasAlFe),  bismuth  oxychloride, 
(BiOCl).  A  few  ternary  compounds  have  names  ending  in  te  (from  ter, 
three),  as  potassium  chlorplatinate,  (K2PtCl0). 

Terminology  of  Acids:  Acids  are  composed  of  the  acid-forming 
elements  in  combination  with  hydrogen  or  with  hydrogen  and  oxygen. 
The  name  of  a  given  acid  is  derived  from  the  name  of  the  acid  forming 
element.  The  best  known  acid  of  an  element  has  the  ending  ic.  Example, 
chloric  acid,  HC1O3.  Then  the  acid  the  molecule  of  which  contains  one 
less  atom  of  oxygen  has  the  ending  ous.  Example,  chlorous  acid,  HC1O2. 
If  the  element  also  forms  an  acid  containing  one  more  atom  of  oxygen  in 
its  molecule  than  the  ic  acid,  it  is  designated  by  the  prefix  per.  Example, 


CHEMICAL  CALCULATIONS  19 

perchloric  acid,  HClO4.  Acids,  like  sulphuric  (H2SO4)  and  ortho  phos- 
phoric (H3PO4),  which  contain  more  than  one  replacable  hydrogen  atom 
are  called,  as  a  class,  polybasic  acids;  and,  in  individual  cases,  the  different 
acids  are  referred  to  as  di  basic,  tri  basic,  etc.,  because  such  acids  may  be 
neutralized  by  more  than  one  base  at  once.  For  example,  potassium  and 
sodium  may  replace  the  two  hydrogens  in  H2SC>4  to  form  sodium  potassium 
sulphate,  NaKSO^  In  all  such  double  salts  both  the  base  forming 
elements  must  appear  in  the  name  of  the  salt. 

Terminology  of  Bases:  The  base  forming  elements  form  compounds 
with  hydrogen  and  oxygen  in  which  these  two  elements  appear  as  a  radical, 
OH,  called  hydroxyl.  Hence,  these  compounds  are  called  hydroxides  in 
wet  chemistry.  Thus,  sodium  hydroxide,  Na  OH,  and  calcium  hydroxide 
Ca  (OH) 2  are  examples.  In  dry  chemistry  the  hydrogen  and  part  of  the 
oxygen  are  driven  off,  leaving  the  oxides  which  still  act  as  acids  and  bases. 

Terminology  of  Salts :  Salts  take  their  names  from  those  of  the  base 
forming  elements  and  the  acids  of  which  they  are  composed,  changing  the 
endings  of  the  acids.  Salts  of  acids  that  end  in  ic  change  this  ending  to 
ate,  and  those  that  end  in  ous«  to  ite.  Thus,  sodium  chlorate  NaClO3, 
derived  from  chloric  acid,  sodium  perchlorate  NaClO4,  from  perchloric 
acid,  and  sodium  chlorite,  NaClO2,  from  chlorous  acid,  are  examples. 
Other  systems  of  nomenclature  are  in  use,  but  the  ones  just  noted  cover 
the  largest  field. 

SECTION   VIII. 

CHEMICAL  CALCULATIONS. 

Kinds  of  Problems:  Chemical  calculations  constitute  a  very  im- 
portant branch  of  study  in  the  training  of  the  metallurgist.  They  are 
of  three  general  classes;  namely,  those  involving  weight,  those  involving 
the  volumes  of  gases,  and  those  involving  both  weight  and  volume.  Further 
subdivisions  of  these  classes  may  be  made,  the  principles  of  which  are  best 
taught  from  specific  examples,  as  follows: 

PROBLEMS   INVOLVING   WEIGHT   ONLY. 

Calculation  of  the  Molecular  Weight  from  the  Formula:     Problem! 
The  formula  of  copper  sulphate  is  CuSO4.     Find  its   molecular  weight. 
Solution:    From  the  table  of  atomic  weights  and  the  formula,  we  find 
Atomic  weight  of  copper  =63.57  Atomic     No.  of    Combining 

"  «        «  sulphur=32.06  Weights    Atoms       Weights 

"  oxygen  =16  63.57    x       1      =      63.57 

32.06    x      1      =      32.06 
16.        x      4     =      64.00 


Molecular  weight  of  CuSO4=    159.63      Ans 


20  CHEMICAL  CALCULATIONS 

Calculation  of  Percentage  Composition  of  a  Compound  from  its 
Formula:  Problem:  Find  the  percentage  composition  of  a  compound, 
the  formula  of  which  is  CuSO4. 

Solution: 

CU  S  OA 


Molecular  weight=63.57+32.06+(4  x  16)=159.63. 

159.63(63.57 32.06 64.00 


Percentage  Composition=39.83%  Copper,  20.09%  Sulphur,  40.09%  Oxygen.  Ans. 

Calculation    of    Formula    from    the    Analysis    of    a    Compound: 

Problem:  By  analysis  a  pure  compound  is  found  to  be  composed  of  calcium 
29.41%,  sulphur  23.53%  and  oxygen  47.06%.  What  is  its  simplest  formula? 

Solution : 

Parts  in  a     Atomic     Atomic  Number  of 

Element      Hundred    Weights      Ratios  Atoms 

Ca      —     29.41     -4-   40.07   =  .735 K735=  1  Ca 

S        —     23.53     -f-   32.06   =  .735+  -K735=  1  S 

O       —     47.06     m»    16.       =2.941— -K  735=  4  O 
Formula  of  compound  is  CaSO4.     Ans. 

Calculation   of   Relative   Weights   from   the   Chemical    Equation: 

Problem:  Five  per  cent,  of  a  certain  limestone  is  non-volatile  impurities 
and  95%  is  pure  calcium  carbonate.  What  will  be  the  weight  of  lime 
obtained  from  calcining  2000  Ibs.  of  this  stone? 

Solution: 

Weight  of  impurities  =5%  of  2000=  100  Ibs. 
"        "  calcium  carbonate          =1900  Ibs. 

Reaction  on  calcining CaCOa  =CaO+CO2 

Combining  or  atomic  wts. .  40.00+12+ (3xl6)=40.+16+12+(2xl6) 
Relative  or  molecular  wts..  100.00       =      56.00     +    44 

100  Ibs.  CaCO3  gives      56  Ibs.  CaO 

1     "          «  "        .56    "       " 

1900    «          "  "      1064    «       " 

1064  Ibs.  CaO+100  Ibs.  non-volatile  impurities=1164  Ibs.  of  lime.     Ans. 

PROBLEMS   INVOLVING   VOLUME   ONLY. 

Calculation  of  Relative  Volumes  of  Gases:  From  Avogadro's 
hypothesis,  it  is  known  that  molecular  weights  of  all  gases  give  the  same 
volume  under  standard  conditions  of  0°C  and  760  mm.  barometric  pressure. 
Problems  involving  volumes  of  gases  only  are,  therefore,  very  simple  to 
solve,  because  the  relative  volumes  are  identical  with  the  coefficients  of 


CHEMICAL  CALCULATIONS  21 

the   molecules,    as   will   be   evident  from   an  inspection  of   the   following 
examples: 

H2+C12=2HC1 
1  vol.  hydrogen+1  vol.  chlorine  gives  2  volumes  hydrochloric  acid  gas 

CH4+2O2=CO2+2H2O 

1  vol.  methane +2  vol.  oxygen  gives  1  vol.  carbon  dioxide +2  vol.  water 
vapor 

N2O2+O2=2NO2 
1  vol.  nitric  oxide +1  vol.  oxygen  gives  2  volumes  nitrogen  peroxide. 

PROBLEMS   INVOLVING    BOTH   WEIGHT  AND    VOLUME. 

Indirect  Method:  This  method  necessitates  finding  the  relative 
weights  of  the  gases  involved,  from  which  the  volumes  may  be  calculated 
from  the  specific  gravity,  or  the  weight  of  a  unit  volume. 

Problem:  How  many  cubic  feet  of  carbon  dioxide  measured  under 
standard  conditions  would  be  given  off  by  2000  Ibs.  pure  calcium  carbonate 
during  the  process  of  calcination? 

Solution: 

Reaction       CaCO3    =  CaO  +  CO2 

40+12+48     40+16     12+2x16 
100  56  44 

100  Ibs.  CaCO3  give  44  Ibs.  CO3 
2000  "  "  "  880  "  CO2 
Wt.  1  cu.  ft.  CO2=.  1235— Ibs. 

880H-.1235  =  7125— cu.  ft.     Ans. 

Direct  Method:  The  fact  that  molecular  weights  of  gases  give 
constant  volumes  at  standard  conditions  affords  a  simple  direct  method 
for  calculating  volumes  from  the  equation.  If  the  weights  are  expressed 
in  grams,  each  gram-molecule  of  the  gases  involved  represents  22.32— liters; 
if  in  kilograms,  each  kilogram-molecule  stands  for  22.32 — cubic  meters; 
and  if  in  avoirdupois  ounces,  each  ounce-molecule  gives  a  volume  of  22  32+ 
cubic  feet.  By  this  method  the  problem  above  would  be  solved  as  follows: 

2000  lbs.=32000  ozs. 

?  cu.  ft. 

CaCO3=  CaO  +    CO2 
40+12+(3xl6)_40+16 
100  56 

100  ozs.  CaCO3  gives  22.32  cu.  ft. 

1     "          "  "      .2232— 

32000     "          "  *      7142  — cu  ft.     Ans. 


22  DESCRIPTION  OF  ELEMENTS 

SECTION   IX. 

A   DESCRIPTION   OF  ELEMENTS   COMMONLY   MET 
WITH   IN   THE    MANUFACTURE   OF   STEEL. 

Oxygen. 

Occurrence:  This  element  is  most  widely  distributed  in  nature; 
49.85%  of  the  solid  crust  of  the  earth,  88.89%  of  water  and  20.8%  of  air 
is  oxygen.  In  air  it  exists  in  a  free  state.  In  a  combined  state,  it  exists 
in  limestone,  sand,  marble,  clay,  quartz,  iron  ore,  and  many  other  substances. 

Preparation:  It  is  prepared  by  merely  heating  certain  of  its 
compounds,  some  of  which  are  mercuric  oxide,  potassium  chlorate  and 
manganese  dioxide;  by  the  decomposition  of  water  by  electrolysis;  and  from 
the  air  by  purifying  processes. 

Properties:  Oxygen  is  a  colorless,  odorless,  tasteless  gas,  heavier 
than  air  (sp.  gr. =1.1056)  and  slightly  soluble  in  water.  At  a  low  temper- 
ature and  a  high  pressure  it  is  converted  into  a  liquid  which  boils  at — 181  °C. 

The  phenomenon  of  ordinary  burning  or  combustion  is  due  to  the 
combination  of  oxygen  with  other  substances.  It  unites  with  many  elements 
to  form  a  class  of  compounds,  the  oxides.  It  is  necessary  to  life.  Animals 
die  in  an  atmosphere  of  less  than  16%  oxygen. 

Compounds:  Some  important  oxides  are:  carbon  dioxide,  CO2, 
carbon  monoxide,  CO,  calcium  oxide,  CaO,  magnesium  oxide,  MgO,  ferric 
oxide,  FeaOa,  and  ferroso-ferric  oxide,  Fe3O4.  The  last  two  are  important 
as  ores  of  iron. 

Hydrogen. 

Occurrence:  Hydrogen  does  not  occur  in  nature  in  a  free  state,  but 
combined  with  oxygen  it  forms  water,  of  which  it  constitutes  11.11%.  In 
a  combined  state  it  occurs  also  in  the  bodies  of  plants  and  animals,  hence, 
in  the  volatile  matter  of  coal,  in  petroleum,  and  in  natural  gas  of  which 
it  constitutes  almost  25%.  Water  is  always  one  of  the  products  of 
combustion  when  a  fuel  containing  hydrogen  is  burned. 

Preparation :  It  can  be  prepared  by  decomposing  water  with  sodium, 
potassium,  hot  iron,  hot  coke,  or  the  electric  current;  by  treating 
certain  metals  with  certain  acids;  and  by  treating  aluminum  with  sodium 
or  potassium  hydroxide. 

Properties:  Hydrogen  is  a  colorless,  tasteless,  odorless  gas,  almost 
insoluble  in  water.  It  can  be  converted  into  a  liquid  that  boils  at — 252°C. 
It  is  the  lightest  substance  known,  being  about  Vis  as  heavy  as  air  and 
VIQ  as  heavy  as  oxygen.  Its  specific  gravity,  air  standard,  is  .0696.  It 
is  combustible  and  explosive.  It  combines  with  oxygen  in  the  proportion 
of  1:8  to  form  water.  Its  great  tendency  to  combine  with  oxygen  makes 
it  an  intense  reducing  agent. 


DESCRIPTION  OF  ELEMENTS  23 

Sulphur. 

Occurrence:  This  element  occurs  free  in  the  neighborhood  of 
volcanoes  and  in  underground  deposits,  from  which  it  may  be  prepared  by 
purifying  processes.  In  combined  state  it  is  found  as  FeS2,  FeCuS2,  ZnS, 
and  PbS,  the  last  three  being  valuable  ores  of  copper,  zinc,  lead,  respectively. 
It  also  occurs  as  the  sulphates  CaSO4,  BaSC>4  and  PbSC>4,  and  in  animal 
and  vegetable  matter.  Compounds  of  sulphur  occur  in  iron  ores,  in 
limestone,  and  in  coal;  and  these  are  reduced  in  the  blast  furnace,  when 
a  varying  part  of  the  sulphur  combines  with  the  iron,  in  which  form  it  is 
very  undesirable,  if  present  in  large  amounts,  on  account  of  its  injurious 
effects  on  steel  and  cast  iron. 

Properties:  Sulphur  is  a  brittle,  yellow  crystalline  solid  which  melts 
at  114.5°,  forming  a  straw  colored  liquid.  It  is  allotropic,  i.  e.,  can  exist 
in  different  physical  forms.  These  forms  are  prismatic,  rhombic  and 
amorphous.  When  heated  to  a  sufficiently  high  temperature,  it  combines 
with  oxygen  to  form  sulphur  dioxide,  SOa,  with  iron  to  form  ferrous  sulphide, 
FeS,  and  with  most  of  the  metals,  forming  sulphides.  The  sulphur  in  iron 
or  steel  is  in  the  forms  of  FeS  and  MnS,  distributed  almost  uniformly 
throughout  the  metal  while  in  the  molten  state.  Upon  solidifying,  however, 
owing  to  the  difference  in  density  and  fusion  temperature  between  these 
compounds  and  the  metal,  they  may,  under  normal  conditions,  segregate 
to  some  extent,  causing  some  parts  of  the  solidified  mass  to  show  a  higher 
content  of  this  impurity  than  the  average,  or  of  the  whole  in  the  molten 
state.  With  hydrogen  it  forms  a  gas,  hydrogen  sulphide,  HaS, — very 
important  in  Chemistry. 

Uses:  Sulphur  is  used  in  the  manufacture  of  matches  and  black  gun 
powder,  also  for  disinfecting  purposes  and  for  vulcanizing  rubber.  Its 
chief  use,  however,  is  in  the  manufacture  of  sulphuric  acid;  and  the 
amount  of  this  acid  consumed  by  a  nation  is  a  measure  of  its  scientific 
advancement. 

Compounds:  Besides  compounds  already  mentioned,  sulphur  forms 
several  acids,  one  of  which,  sulphuric  acid,  HaO*  SOg  (H^SO^,)  is  a  most 
important  compound.  It  is  obtained  by  oxidizing  sulphur  dioxide,  SO2, 
which  is  given  off  as  a  gas  from  the  roasting  of  FeS2,  ZnS,  CuS,  and  from 
the  burning  of  sulphur. 

Carbon. 

Occurrence:  This  element  occurs  free  in  nature  in  crystalline  forms 
as  diamonds  and  graphite  and  in  the  amorphous  form  as  coal.  It  is  the 
chief  constituent  of  the  bodies  of  plants  and  animals,  of  all  natural  fuels, 
and  of  nearly  all  prepared  fuels.  It  occurs  in  combined  state  in  limestone, 
magnesite,  marble  and  other  carbonate  rocks. 

Properties:  Carbon  is  allotropic;  diamond  and  graphite  have  been 
mentioned.  The  common  amorphorous  forms  are  coal,  lampblack,  charcoal, 
coke,  bone  black  and  gas  carbon.  Its  density  varies  with  its  form. 


24  DESCRIPTION  OF  ELEMENTS 

Compounds  and  Uses:  Carbon  forms  many  compounds  with 
hydrogen,  called  hydrocarbons,  as  methane  CH4,  ethylene  CsEU,  benzene 
CeHe,  acetylene  CaH's,  each  of  which  is  but  the  first  member  of  a  series 
of  related  compounds.  With  oxygen  it  forms  carbon  dioxide,  CO  2  which 
is  a  product  of  combustion  and  of  respiration.  CO '2  is  also  given  off  when 
carbonates,  such  as  limestone,  are  heated.  The  reaction  is,  CaCO3=CaO 
+CO2.  Carbon  monoxide  is  formed  in  combustion  when  the  supply  of 
oxygen  is  insufficient  for  the  formation  of  CO 2.  Thus,  in  the  blast  furnace, 
a  fixed  amount  of  air  is  blown  against  an  excess  of  hot  carbon,  which  act 
results  in  this  reaction:  2C+O2=2CO.  Owing  to  its  tendency  to  combine 
with  oxygen,  forming  CO 2,  CO  is  a  good  reducing  agent.  So,  the  CO  formed 
before  the  tuyeres  of  the  blast  furnace  reacts  with  the  iron  oxide  thus: 

3  CO+Fe2O3=3CO2+2  Fe. 

Carbon  alone  acts  as  a  reducing  agent  in  the  metallurgy  of  iron. 
3C+Fe'203=2  Fe+3  CO. 

Iron  forms  a  carbide  with  carbon,  the  formula  of  which  is  FesC.  In 
pig  iron  it  is  also  found  uncombined  in  the  form  of  tiny  flakes  of  graphite, 
hence  the  term  graphitic  carbon.  Carbon  has  a  marked  effect  upon  iron. 
The  varying  properties  of  steel  and  the  many  uses  to  which  it  can  be  applied 
are  due  largely  to  the  influence  of  this  element.  Carbon  in  steel,  then,  up 
to  a  certain  limit,  is  not  to  be  considered  as  an  impurity  but  as  an  essential 
factor. 

Silicon. 

Occurrence:  Next  to  oxygen,  silicon  is  the  most  abundant  element 
in  nature.  It  is  the  most  important  constituent  of  the  mineral  part  of  the 
earth.  Sea  sand,  quartz,  jasper,  opal  and  infusorial  earths  are  almost 
pure  forms  of  SiO2.  As  silicates,  it  occurs  in  clay,  mica,  talc,  hornblend 
and  feldspar.  On  account  of  its  wide  distribution  it  forms  the  chief  impurity 
of  iron  ore,  as  well  as  of  nearly  all  natural  mineral  deposits. 

Compounds:  As  already  indicated  silica,  SiOa,  is  one  of  the  chief 
compounds  of  silicon.  It  also  forms  several  acids,  chief  of  which  is  silicic 
acid,  2H2O.SiO2  (H^SiO^  which  loses  water  when  heated  and  forms  SiOs. 
H4SiO4=SiO'2+2H20. 

Thus,  in  whatever  form  silicon  may  occur  in  an  ore,  it  is  looked  upon 
as  SiO2-  This  substance  is  the  great  acid  of  dry  chemistry  and  at  high 
temperatures  will  neutralize  any  base  with  which  it  comes  in  contact.  In 
the  blast  furnace  some  of  the  silica  (SiO2)  contained  in  the  charge  is  reduced 
to  silicon.  The  amount  so  reduced  varies  with  the  working  conditions  of  the 
the  furnace,  mainly  the  temperature.  Once  reduced,  the  silicon  alloys 
with  the  iron  and  becomes  a  part  of  the  metallic  bath.  All  but  traces  of 
this  silicon  is  re-oxidized  and  removed  in  the  various  processes  of  making 
steel.  However,  a  little  is  beneficial  to  steel,  so  it  is  sometimes  added  in 
small  amounts  in  the  form  of  an  iron  alloy. 


DESCRIPTION  OF  ELEMENTS  25 

Nitrogen. 

Occurrence  and  Properties:  This  element  occurs  in  niter  beds  as 
saltpeter,  KNO3,  and  Chili  saltpeter,  NaNO3,  also  in  organic  compounds 
and  in  coal.  It  is  an  odorless,  tasteless,  colorless  gas  that  constitutes 
about  78%  of  the  atmosphere. 

Compounds:  With  hydrogen  it  forms  ammonia,  NH3;  with  oxygen  a 
series  of  oxides,  N2O,  NO,  N2O8,  N2O5  and  NO2;  and  with  hydrogen  and 
oxygen,  an  important  acid,  H2O-N2O5  (HNO3).  It  is  a  very  inert  element 
and  has  very  slight  effects  in  the  manufacture  of  steel.  Nevertheless,  its 
presence  in  the  air  in  so  large  amounts  makes  it  an  important  factor  in 
blast  furnace  practice. 

Phosphorus. 

Occurrence:  Phosphorus,  always  combined  with  other  elements, 
occurs  widely  distributed  in  limited  amounts,  particularly  in  soils.  It  is, 
therefore,  found  in  all  iron  ores.  It  occurs  in  deposits  as  phosphorite  and 
apatite,  and  is  an  important  constituent  of  bone. 

Properties  and  Compounds:  While  phosphorus  belongs  in  the  same 
group  of  elements  as  nitrogen,  it  does  not  much  resemble  it  from  a  physical 
standpoint.  It  is  allotropic  and  exists  in  two  forms,  as  a  pale  yellow  solid 
that  melts  readily  at  the  low  temperature  of  44.1°C,  and  as  a  red  form 
quite  different  in  properties.  While  it  is  a  much  more  active  element,  it 
closely  resembles  nitrogen  chemically.  It  forms  compounds  with  hydrogen 
and  oxygen,  such  as  PHs  and  P2O5,  and  an  acid,  H2O.P2O5  (HPO3),  called 
metaphosphoric  acid.  It  generally  is  found  in  nature  as  salts  of 
orthophosphoric,  3H2O.P2O5  (H3PO4),  and  pyrophosphoric,  2H2O.P2O5 
(H4P2O7),  acids.  With  iron  it  forms  a  phosphide,  FeaP.  It  is  completely 
reduced  in  the  blast  furnace,  hence  all  the  phosphorus  occurring  in  the  raw 
materials  is  found  in  the  pig  iron.  In  steel  it  is  a  very  undesirable  impurity, 
but  fortunately  it  is  oxidized  readily,  when  it  can  be  neutralized  with 
lime  and  easily  removed  as  part  of  a  slag. 

Calcium  and  Magnesium. 

While  these  two  elements  belong  to  different  groups,  they  are  very 
similar  so  far  as  the  manufacture  of  iron  and  steel  are  concerned.  With 
few  exceptions  one  may  be  substituted  for  the  other  without  great 
inconvenience.  Their  oxides  are  the  more  important  bases  of  dry  chemistry. 

Occurrence  and  Chief  Compounds :  Both  elements  occur  as  insoluble 
carbonates;  limestone,  marble,  chalk  and  marl  are  forms  of  calcium  car- 
bonate, CaO.CO2  (CaCO3).  Magnesite  is  magnesium  carbonate,  MgCO3. 
When  heated,  both  these  compounds  decompose  into  the  oxides  and  carbon 
dioxide,  thus: 

CaCO3=CaO-hCO2. 

MgCO3=MgO-hCO2. 
CaO  represents  quick  lime,  and  MgO,  magnesia. 


26  DESCRIPTION  OF  ELEMENTS 

These  elements  also  occur  together  as  a  double  salt  of  carbonic  acid, 
calcium  magnesium  carbonate,  CaMg  (CO8)2,  commonly  called  dolomite, 
which  gives  calcium  magnesium  oxide  CaO- MgO  when  calcined. 
CaMg  (CO8)2=CaO-MgO+2  CO2. 

Uses  of  Lime  and  Magnesia:  Lime,  CaO,  Magnesia,  MgO,  and  the 
double  oxide,  CaOMgO,  are  all  very  refractory.  But  on  account  of  its 
tendency  to  slake  in  air,  CaO  is  not  used  as  such.  Practically,  MgO  is 
the  best  basic  refractory  known,  and  calcined  dolomite  is  the  best  available 
substitute. 

The  oxides  are  reduced  with  difficulty,  and  on  account  of  their  cheapness 
constitute  the  principal  basic  fluxes.  As  MgO  is  the  leading  basic 
refractory,  CaO  is  the  leading  basic  flux.  It  combines  with  both  silica  and 
phosphoric  acid  to  form  readily  fusible  slags,  which  have  a  lower  density 
than  iron  and  consequently  lie  upon  the  surface  of  the  metallic  bath. 

Aluminum. 

Occurrence  and  Properties :  This  element  in  combined  form  is  very 
widely  distributed,  occurring  as  one  of  the  constituents  of  feldspar,  granite, 
mica,  cryolite,  and  all  clays.  It  is  reduced  from  the  oxide,  A12O8,  by  an 
electrolytic  process,  in  which  state  it  is  applied  to  many  uses.  It  has  a 
strong  affinity  for  oxygen,  violently  reducing  iron  oxide,  and  on  this  account 
it  is  added  to  steel  as  a  deoxidizing  agent. 

Compounds:  In  its  compounds  aluminum  displays  decidedly  basic 
properties,  forming  salts  with  all  the  common  acids  except  carbonic  acid. 
It  forms  neither  a  carbonate  nor  a  sulphide.  Aluminum  hydroxide, 
Al  (OH)8,  however,  acts  like  both  an  acid  and  a  base.  When  this  compound 
is  heated,  it  loses  water  and  forms  alumina,  A^Os-  It  is  found  in  varying 
amounts  in  all  the  raw  materials  that  enter  into  the  metallurgy  of  iron. 
In  the  blast  furnace  it  is  never  reduced.  Its  presence,  however,  has  a 
marked  influence  on  the  slag,  affecting  its  fluidity  and  fusion  temperature, 
important  considerations  in  blast  furnace  practice.  In  its  purer  states 
alumina  is  a  good  refractory,  but  its  scarcity  prohibits  its  extensive  use 
as  such. 

Chromium. 

Occurrence:  This  element  is  somewhat  rare.  In  small  deposits  it  is 
found  as  chromite,  Cr2O8-FeO.  This  substance  is  the  best  neutral  refrac- 
tory known.  In  its  purer  states  it  melts  at  about  2175  °C. 

Properties  and  Uses:  Chromium  is  both  acid  and  basic  in  character. 
It  is  very  important  in  the  manufacture  of  alloy,  or  special  steels.  Its 
chief  effect  is  one  of  hardening,  hence  it  is  employed  to  increase  the  hardness 
of  projectiles,  armor  plate,  automobile  steel,  and  tool  steels. 


DESCRIPTION  OF  ELEMENTS  27 

Manganese. 

Occurrence:  This  element  occurs  in  nature  as  MnO2,  its  deposits 
being  somewhat  limited  in  the  United  States.  In  very  small  amounts  it 
is  widely  distributed,  and  is  found  in  nearly  all  raw  materials  of  iron  manu- 
facture. About  75%  of  this  manganese  is  reduced  in  the  blast  furnace,  so 
it  is  a  constituent  of  all  pig  iron.  But  it  is  readily  oxidized  in  the  purifying 
processes,  and  except  for  almost  traces,  that  found  in  steel  is  added  to  it 
in  the  process  of  manufacture.  Its  effect  in  steel  up  to  1.0%  is  good, 
because  it  offsets  the  evil  effects  of  oxygen  and  sulphur.  Higher  per- 
centages, 7%  to  15%,  are  employed  to  produce  the  special  steel  known  as 
manganese  steel. 

Iron. 

Occurrence:  This  most  important  metal  occurs  in  combined  states 
and,  in  slight  amounts,  in  nearly  all  earthy  matter,  as  clays,  soils,  sands, 
etc.  In  deposits,  it  is  found  as  the  sulphide,  FeS2,  as  silicates,  as  a  con- 
stituent of  chromite,  as  the  carbonate,  FeCOs,  and  as  the  oxides,  Fe2Os 
and  FegOv  The  compound  last  named  is  magnetic. 

Properties:  Pure  iron,  almost  unknown,  is  somewhat  unlike  the 
ordinary  commercial  forms.  It  is  grayish-white  in  color  and  relatively  soft 
when  compared  with  steel  of  high  carbon  content.  It  is  malleable,  ductile, 
and  magnetic.  Its  specific  gravity  is  7.78,  and  its  melting  point  in  its  purest 
commercial  form  is  about  1520  °C.  The  presence  of  certain  elements,  notably 
carbon,  silicon,  phosphorus  or  sulphur,  in  the  metal  lowers  the  melting  point 
rapidly. 

Compounds:  Iron  forms  two  series  of  compounds,  the  ferrous  and 
the  ferric.  The  more  important  ferrous  compounds  are  FeO,  Fe  (OH)2, 
FeCl2,  FeSC>4'7H2O;  corresponding  ferric  compounds  are  Fe2O8,  Fe  (OH)8, 
FeCl3,  Fe2  (804)3.  Most  of  these  compounds  are  of  the  highest 
commercial  importance,  and  many  will  receive  much  fuller  treatment  as 
this  course  advances. 


28  REFRACTORIES 


CHAPTER  II. 

i 

REFRACTORIES. 

SECTION   I. 

NATURE   OF   REFRACTORIES. 

Importance:  The  problem  of  obtaining  refractories  suitable  for  each 
particular  operation  is  one  of  supreme  importance  in  the  metallurgical  arts, 
especially  in  the  manufacture  of  steel.  They  form  the  chief  materials  of 
which  all  furnaces  and  retaining  vessels  are  made,  as  well  as  flues  and 
stacks  through  which  hot  gases  are  conducted.  This  equipment  is 
expensive,  and  any  failure  in  the  refractories  results  in  a  great  loss  of 
time,  equipment  and  product,  and,  too  often,  in  loss  of  life  as  well. 

Requirements  of  Refractories:  A  refractory  may  be  denned  as  any 
substance  which  is  infusible  at  the  highest  temperature  it  may  be  required 
to  withstand  in  service.  In  any  particular  application  however,  this  definition 
is  incomplete,  because  the  fact  that  a  substance  is  infusible  does  not  alone 
determine  its  value  as  a  refractory.  An  almost  infusible  brick,  for  example 
may  be  so  fragile  as  to  be  worthless,  since  bricks  are  generally  required  to 
support  a  load  in  addition  to  resisting  the  effects  of  great  heat.  A  perfect 
refractory  would  meet  the  following  requirements  at  any  temperature:  (1) 
it  would  not  fuse  or  soften;  (2),  it  would  not  crumble  or  crack;  (3),  its  contrac- 
tion and  expansion  would  be  the  minimum;  (4),  it  would  not  conduct  heat; 
(5),  it  would  be  impermeable  to  gases  and  liquids;  (6),  it  would  resist  mech- 
anical abrasion;  (7),  it  would  not  react  chemically  with  substances  in  contact 
with  it.  Needless  to  say,  an  absolutely  perfect  refractory  has  never  been 
discovered.  However,  there  are  a  number  of  substances  which  closely 
approach  the  first  six  requirements,  at  temperatures  commonly  employed 
in  metallurgical  work,  and  whether  or  not  they  will  meet  the  seventh 
depends  upon  their  chemical  composition  and  the  nature  of  the  substances 
with  which  they  are  in  contact. 

Classes  of  Refractories:  Refractory  substances,  in  common  with  matter 
in  general,  are  of  three  classes:  namely,  acid,  basic  and  neutral.  Recalling 
the  chemical  action  of  acids  and  bases  toward  each  other,  it  is  at  once 
apparent  that  a  refractory  of  an  acid  character  is  useless  in  contact  with 
a  basic  slag,  and  vice  versa.  In  selecting  a  refractory  for  a  specific  purpose, 
the  first  question  to  be  decided  is  what  class  of  refractory  will  be  required. 
Other  factors  affecting  its  life  and  usefulness  are  the  amount  of  impurities 
it  contains  and  the  uniformity  of  its  composition;  and,  in  the  case  of  brick, 


ACID  REFRACTORIES  29 

to  these  will  be  added  strength,  toughness,  porosity,  or  other  special 
qualities.  In  the  manufacture  of  prepared  refractories  these  factors  are  all 
under  control,  depending  upon  the  selection  of  materials  and  the  method 
of  manufacture. 

SECTION   II. 

ACID    REFRACTORIES. 

Chemical  Composition:  Acid  refractories  owe  their  acid  character 
only  to  silica,  SiO^,  and  are  of  two  kinds,  namely,  those  composed  mainly  of 
silica  and  those  composed  of  aluminum  silicate,  or  clay.  In  the  pure  state 
silica  fuses  at  a  very  high  temperature,  about  1830°  C,  a  temperature  much 
above  that  obtained  in  ordinary  furnaces,  but  when  heated  in  contact  with 
basic  substances  it  forms  silicates,  some  of  which  are  easily  fused.  Hence, 
in  refractories  composed  of  silica  the  presence  of  impurities,  alumina  as  well 
as  the  stronger  bases,  must  be  guarded  against.  As  a  refractory,  silica  is  used 
in  the  natural  forms  of  sand  and  cut  stone  and  in  the  prepared  form  of 
brick.  Sand  (90%to  99.5%  SiC>2)  is  used  to  make  up  the  bottoms  of  acid 
open  hearth  furnaces  and  of  some  types  of  heating  furnaces.  Ganister, 
a  very  superior  material  for  lining  converters,  is  a  highly  silicious  rock.  It 
has  a  silica  content  of  about  98%. 

Silica  Bricks  are  prepared  from  quartzite  rock  found  in  Pennsylvania, 
Wisconsin  and  Alabama.  The  rock  is  first  crushed  fine,  then  intimately 
mixed  with  a  binding  material  which  acts  as  a  cement  to  hold  the  particles  of 
silica  together  and  to  give  the  brick  the  necessary  strength.  For  this  purpose 
either  clay  or  lime,  usually  in  the  form  of  milk  of  lime,  is  used,  the  former 
to  produce  quartzite  brick  and  the  latter,  "silica"  or  ganister  brick.  The 
mixture,  in  a  moist  condition,  is  next  compressed  and  moulded  into  the  shape 
desired  for  the  bricks,  which  are  allowed  to  dry  slowly  and  then  are  burned  at 
high  temperatures, about  1500°  C.,in  large  kilns.  From  seven  to  ten  days 
are  required  to  complete  the  burning.  Silica  brick  expands  slightly  when 
heated. 

Clay  is  a  natural  occurring  earthy  material  which  has  the  property  of 
plasticity  when  wet  but  becomes  hard  when  burned.  The  ordinary  varieties 
are  more  or  less  impure  silicates  of  aluminum,  formed  by  the  decomposition, 
or  weathering,  of  feldspathic  rock,  and  contain  high  percentages  (10%  to  15%) 
of  combined  water.  They  may  be  residual  or  sedimentary.  Fire  clays 
are  of  two  varieties,  known  as  plastic  and  flint  clays;  the  latter  is  very 
hard,  even  when  ground,  but  very  refractory.  The  most  refractory  clays 
are  associated  with  the  coal  measures  of  Pennsylvania. 

The  impurities  in  clays  are  alkalies,  due  to  undecomposed  feldspar; 
sand;  gravel;  iron  oxide,  silicate  or  sulphide;  calcium  and  magnesium 
silicates  or"  carbonates;  titania;  and  organic  matter.  Of  these  impurities, 


30  BASIC   REFRACTORIES 

the  basic  oxides  are  the  most  harmful,  as  they  lower  the  fusion  point 
decidedly.  This  is  due  to  the  fact  that  aluminum  silicate  combines  with 
bases,  forming  double  silicates. 

The  process  of  making  fire  clay  brick  is  similar  to  that  for  silica 
brick.  The  clay,  in  a  finely  crushed  condition,  is  moistened  with  a  definite 
amount  of  water  and  thoroughly  mixed.  When  flint  clay  is  being  used, 
some  plastic  clay  is  used  as  a  binder.  Upon  being  dried,  clay  begins  to 
shrink  and  continues  to  do  so  during  the  burning,  when  the  combined  water 
is  driven  off  and  the  brick  becomes  hard.  Thus,  a  brick,  9  inches  in 
length  after  being  burned,  may  measure  from  9^  to  9^  inches  when 
moulded,  depending  on  the  mixture  used.  Calcined,  or  burnt  clay  is 
employed  in  the  mixtures  to  control  the  shrinkage.  Once  burned,  the  brick 
ceases  to  shrink  and  permanently  loses  the  property  of  plasticity,  which 
latter  fact  would  indicate  that  the  plasticity  is  due  to  combined  water. 
The  refractory  properties  of  a  brick  depend  upon  the  nature  and  amount 
of  impurities  and  the  ratio  of  silica  to  alumina.  Besides  its  use  as  brick, 
clay  is  important  as  a  refractory  mortar  to  be  used  in  laying  bricks  in 
furnaces  and  ladles,  and  as  plaster  where  seamless  linings  are  required. 


SECTION   III. 

BASIC   REFRACTORIES. 

Magnesia,  with  a  melting  point  of  2165 °C  is,  for  practical  purposes, 
the  most  satisfactory  basic  refractory.  It  is  prepared  by  calcining  the 
mineral  magnesite,  a  natural  carbonate  of  magnesium.  Large  deposits  are 
somewhat  rare.  In  this  country  very  pure  deposits  had  long  been  known 
to  exist  in  the  states  of  California  and  Washington,  but  up  to  the  outbreak 
of  the  World  War  the  entire  supply  was  obtained  from  Austria  and  Hungary. 
Now,  however,  the  demand  is  supplied  almost  wholly  from  the  State  of 
Washington.  For  this  reason  it  is  an  expensive  material,  which  fact  accounts 
for  its  not  being  used  except  where  a  basic  substance  of  the  highest 
refractoriness  is  required.  It  makes  an  ideal  brick  for  the  construction  of 
basic  furnaces,  and  is  used  for  the  inner  courses  of  bottoms  and  walls  to 
slightly  above  the  slag  line.  In  a  coarsely  crushed  form,  described  as  pea 
size,  it  is  very  desirable  material  for  making  up  bottoms  in  basic  furnaces, 
as,  mixed  with  a  small  percentage  of  basic  cinder,  it  is  readily  fritted,  forming 
a  solid  mass  that  resists  chemical  and  mechanical  action  of  the  charge  and  the 
buoyant  force  of  the  bath. 

Lime  is  even  more  refractory  than  magnesia,  resisting  the  intense  heat 
of  the  oxyhydrogen  flame,  but  on  account  of  its  slaking  properties  it  is  of 
little  practical  value  as  a  refractory.  Mixed  with  magnesia  it  gives  satis- 
factory results. 


NEUTRAL  REFRACTORIES  31 

Dolomite,  fortunately,  furnishes  such  a  mixture  and  occurs  in  this 
country  in  abundant  quantities.  Upon  calcining  the  mineral,  a  mixture  of 
lime  and  magnesia  in  the  best  proportions  is  obtained.  It  cannot  be  fritted 
on  a  bottom  as  well  as  magnesite,  and  the  lime  content  fastens  upon  it  a 
tendency  to  slake.  In  the  steel  industry  it  is  used  chiefly  for  making  up 
the  banks  of  basic  open  hearth  furnaces. 

Bauxite  is  a  natural  form  of  the  sesquioxide  of  aluminum,  mixed  with 
varying  amounts  of  earthy  matter  and  the  corresponding  oxide  of  iron. 
It  usually  contains  one  per  cent,  or  more  of  titania,  TiO2.  It  is  but  feebly 
basic  and,  when  free  from  silica,  is  highly  refractory.  In  pure  form  alumina 
melts  at  2010  °C.,  but  the  fusion  temperature  of  the  natural  bauxite  will 
seldom  exceed  1820°C.  Recent  trials  indicate  that  it  may  prove  to  be  an  ex- 
cellent lining  material,  but  its  scarcity  precludes  its  general  use. 

SECTION    IV. 

NEUTRAL   REFRACTORIES. 

The  Ideal  Furnace  Lining  is  a  neutral  material,  a  substance  that  will 
permit  of  changing  from  acid  to  basic,  or  basic  to  acid,  processes  on  the  same 
lining.  Two  such  substances  are  well  known,  but  unfortunately  the  con- 
ditions of  natural  deposits  will  not  permit  of  their  use  except  in  restricted 
quantities.  These,  are  graphite  and  chromite. 

Graphite:  This  substance  is  a  natural  product,  though  it  can  be 
prepared  artifically  in  small  quantities.  It  occurs  mixed  with  calcareous  or 
silicious  rocks  in  Ceylon,  Siberia,  Austria,  England,  Brazil  and  New  York. 
It  requires  expensive  purification.  It  is  infusible  even  at  the  temperature  of 
the  electric  arc,  but  burns  rapidly  at  that  temperature,  forming  CO  or  CC>2. 
At  the  temperature  of  the  open  hearth  it  would  be  very  slowly  consumed. 
It  is  used  in  making  special  brick,  crucibles,  etc.  Clay  may  be  used  as  a 
binding  material. 

Chromite  most  nearly  approaches  the  ideal  refractory.  Experience 
proves  it  to  give  equally  satisfactory  results  in  either  an  acid  or  a  basic 
process.  Its  fusion  point,  about  2180 °C.,  is  far  above  the  highest  working 
temperature  of  the  open  hearth  or  blast  furnace.  It  is  difficult  to  set  or 
sinter.  In  a  finely  ground  condition  and  mixed  with  the  proper  proportion 
of  slag  also  finely  ground,  it  is  used  regularly  in  the  open  hearth  to  daub 
ports  and  jambs  and  patch  walls  near  the  slag  line.  In  the  form  of  brick  it 
is  used  as  dividing  courses  to  separate  acid  from  basic  bricks,  and  in  the 
bottoms  of  soaking  pits,  because  it  is  impervious  to  pit  cinder.  The  binding 
material  for  chromite  brick  is  lime,  or  clay  and  lime. 

Protection  for  Refractories:  The  fusion  temperature  of  the  materials 
discussed  is  amply  high  to  withstand  the  temperatures  of  carbon  heated 


32 


REFRACTORIES 


furnaces,  if  resistance  to  heat  were  the  only  requirement.  But  the 
refractory  must  possess  strength,  resistance  to  abrasion  and  corrosion,  etc., 
and  as  these  properties  decrease  rapidly  with  increase  of  temperature,  it 
is  desirable,  in  some  cases  necessary,  to  protect  them  as  much  as  possible 
from  the  heat.  This  end  is  accomplished  by  backing  the  brick  work  with 
hollow  metal  forms  through  which  water  is  kept  constantly  flowing.  These 
forms  are  made  of  cast  iron,  steel,  copper,  or  bronze,  depending  upon  their 
use  and  position  in  the  furnace,  and  may  be  in  the  shape  of  coiled  pipes, 
hollow  boxes,  or  sprayed  jackets.  As  this  course  progresses,  these  devices 
will  be  frequently  met  with  and  their  value  demonstrated. 

For  purposes  of  comparison  typical  analyses  of  the  various  refractories 
will  be  found  in  the  following  table: 


NAME 


Table  3.     Chemical  Analyses  of  Refractories. 

PERCENT  OF 


Silica 
Si02 

Iron    Oxides 

Alum- 
ina 

A1208 

Lime 
CaO 

Mag- 
nesia 

MgO 

Soda. 
Na20 

Potash 
K20 

Water 
H20 

Ti- 
tania 

Ti02 

Chro- 
mic 

Oxide 
Cr203 

Mang- 
anese 
Oxide 
MnO 

Car- 
bon 

C 

Fe203 

FeO 

Canister 
Low  Grade 
Silica  Sand  .  . 
High  Grade 
Silica  Sand.. 
Silica  Brick  .  .  . 
Low  Grade 
Fire  Clay.... 
High  Grade 
Fire  Clay.... 
Low  Grade  Fire 
Clay  Brick... 
High  Grade  Fire 
Clay  Brick... 
Calcined 
Magnesite  .  .  . 
Calcined 
Dolomite  
Bauxite  
Bauxite  Brick  . 
Chromite  
Artificial 
(Coke—  tar) 
Graphite.... 
Natural 
Graphite 
Brick  

98.20 
91.60 

99.25 
96.42 

60.50 
50.35 
61.72 
53.52 
3.96 

1.66 
4.10 
8.82 
9.36 

5.95 
13.04 

.30 
3.48 

.31 

.50 

2.35 
.75 
6.43 
2.00 
5.81 

.94 
3.20 

6.30 

.40 

13.50 
2.15 
.44 

.90 
3.68 

.20 
.75 

24.95 
33.65 
28.70 
41.00 
1.95 

1.24 
60.80 
78.01 
10.60 

3.04 
6.12 

.15 
.10 

Trace 
2.01 

.25 
.10 
.46 
.30 
.40 

55.01 
.04 
.98 
Trace 

.43 

.10 
.05 

Trace 
.08 

.05 
.05 
1.04 
.30 

87.45 

38.26 
.04 
4.41 
21.06 

.20 

Trace 

Trace 

.06 

.15 
.10 
.05 
.90 

.40 
.05 
.20 

10.00 
13.75 

1.40 

.80 
1.60 
1.60 

.10 

30.08 

1.62 
1.16 

43.97 

.80 

88.20 
77.80 

.43 

1.95 



TESTING  REFRACTORIES  33 

SECTION   V. 

TESTING   REFRACTORIES. 

Trial  Tests  and  Laboratory  Tests:  The  best  test  fora  refractory  is 
a  trial  test  in  which  the  material  is  placed  in  actual  service  under  the  most 
trying  conditions  it  will  be  expected  to  stand  up  under.  As  such  tests  can 
seldom  be  made  on  material  for  new  work  and  as  there  may  be  considerable 
variation  in  raw  materials  and  in  methods  of  manufacture,  laboratory  tests 
are  necessary.  Such  tests  are  not  always  conclusive,  owing  to  the  difficulty 
of  obtaining  laboratory  conditions  identical  to  those  in  actual  practice. 
They  are,  however,  very  useful  for  the  purpose  of  comparisons,  and,  if  the 
conditions  of  the  tests  are  sufficiently  severe,  the  more  serious  defects  will 
be  revealed.  These  tests  are  chemical  and  physical.  From  the  chemical 
analysis  the  composition  of  the  material  is  determined  and  its  quality  is 
judged.  As  the  method  of  manufacture  and  the  care  with  which  it  is  carried 
out  affect  the  properties  of  the  refractory,  the  chemical  test  should  be, 
and  usually  is,  supplemented  by  physical  tests.  Chief  among  these  tests 
are  the  fusion  or  softening  point,  crushing  strength,  expansion  and  con- 
traction, slagging,  porosity,  density,  resistance  to  compression,  impact, 
abrasion  and  spalling  tests.  Each  of  these  tests  may  be  made  in  a  compara- 
tively simple  manner,  but  care  and  judgment  are  required  to  see  that  the 
conditions  of  the  tests  conform  closely  with  those  to  which  the  brick  are 
to  be  subjected  in  actual  service.  On  this  account  some  of  the  tests 
usually  employed  will  not  be  applicable  to  the  iron  and  steel  industry, 
while  others  must  be  modified  to  conform  to  its  conditions.  The  tests 
here  described  are  those  particularly  suited  to  this  industry.1 

The  fusion  temperature,  in  ordinary  practice,  is  usually  determined 
by  means  of  Seger  cones.  These  are  small  triangular  pyramids,  6  cm. 
high,  with  a  base  of  2  cm.  They  are  composed  of  aluminum  silicates.  Cone 
number  28  contains  ten  parts  silica  to  one  part  alumina  and  corresponds 
to  a  temperature  of  1630°  C.  The  fusion  temperatures  of  succeeding  cones 
up  to  number  40,  which  corresponds  to  a  temperature  of  1920°  C,  are  increased 
by  decreasing  the  proportion  of  silica  to  alumina.  For  lower  temperatures 
varying  amounts  of  alkali  or  lime  are  added.  By  this  means  the  melting  point 
is  so  controlled,  that  a  series  of  cones  may  be  prepared  with  melting  points 
between  the  limits  of  500°  and  1900°  .  Upon  being  gradually  heated  to  a 
sufficiently  high  temperature,  these  cones  will  soften  and  slowly  bend  until 
their  tops  touch  the  floor,  which  point  is  taken  as  their  fusion  point.  In 
making  a  test,  a  pyramid  of  the  material  to  be  tested,  having  the  same  shape 
and  dimensions  as  the  standards,  is  placed  in  a  furnace  with  two  or  more 
standards  having  melting  points  estimated  to  be  near  that  of  the  material 
to  be  tested.  As  the  temperature  of  the  furnace  is  raised,  the  standard  cone 
that  melts  at  the  same  time  as  the  test  will  register  the  temperature  of  the  f  ur- 

JSee  Practical  Methods  for  Testing  Refractory  Fire  Brick  by  C.  E.  Nesbitt  and 
M.  L.  Bell.  Proceedings  of  the  American  Society  for  Testing  Materials.  Vol. 
jL.  v  IIt  1016. 


34  TESTING  REFRACTORIE^ 

nace  and  the  fusion  point  of  the  test.  The  softening  temperature  is  considered 
to  be  that  at  which  the  specimen  bends,  sags  or  puffs  out  of  shape.  Instead 
of  the  standard  cone,  the  more  accurate  pyrometer  is  coming  into  use  for 
making  this  test. 

Resistance  to  Compression:  The  ability  of  brick  to  withstand 
pressure  at  a  high  temperature  is  a  very  important  property.  This  test 
is  made  on  a  modified  form  of  Brinell  ball  testing  machine.  The  ball  is 
made  of  steel  and  is  2K  inches  in  diameter.  In  making  this  test,  the  brick 
is  uniformly  and  slowly  heated  from  atmosphoric  temperature  to  1350°  and 
held  in  the  furnace  at  this  temperature  for  three  hours  or  longer,  when  it 
is  removed  and  placed  flat  under  the  ball  of  the  machine,  and  a  pressure 
of  850  Ibs.  is  immediately  applied,  which  is  gradually  and  uniformly  increased 
at  such  a  rate  that  a  maximum  load  of  1600  Ibs.  is  attained  at  the  end  of 
five  minutes.  The  depth  of  the  depression  made  by  the  ball  is  taken  as  the 
measurement  of  the  resistance  of  the  brick  to  compression. 

Expansion  and  Contraction :  A  brick  must  be  prepared  for  this  test 
by  grinding  the  ends  so  that  they  will  be  parallel  to  each  other  and  at  right 
angles  to  the  sides.  Its  length  is  then  measured  by  means  of  a  specially 
constructed  micrometer.  The  brick  is  next  heated  to  the  temperature  at 
which  it  is  to  be  used,  removed  from  the  furnace  and  immediately  measured. 
The  expansion  or  contraction  is  expressed  in  inches  per  lineal  foot. 

Slagging  Test :  By  this  test  the  impermeability  of  the  brick  to  molten 
slag  is  determined.  The  brick  is  prepared  by  drilling  two  circular  cavities, 
2^  inches  in  diameter,  each  at  the  intersection  of  the  diagonals  of  the 
rectangles  formed  by  bisecting  transversely  the  unbranded  face  of  the 
brick,  to  such  a  depth  that  the  area  of  the  greatest  cross  section  is  1.7 
inches.  The  brick  is  then  heated  as  in  the  compression  test.  When  the 
temperature  has  reached  1350°,  35  grams  of  a  standard  blast  furnace  slag  is 
placed  in  one  cavity  and  35  grams  of  a  standard  heating  furnace  slag  in  the 
other.  Both  slags  are  pulverized  to  pass  a  40  mesh  sieve.  The  temperature 
of  1350°  is  maintained  for  two  hours  after  the  slag  is  added,  at  the  end  of 
which  time  the  brick  is  removed  from  the  furnace  and,  when  cold,  sawed 
lengthwise  so  as  to  bisect  both  cavities,  thus  exposing  the  part  of  the  brick 
subject  to  slag  penetration.  The  area  penetrated  by  the  slag  is  measured 
with  a  planimeter  and  expressed  in  square  inches. 

Density:  The  density  is  determined  from  the  weight  of  the  brick  in 
air  and  its  dimensions.  This  method  gives  the  apparent  specific  gravity. 
This  test  is  greatly  influenced  by  the  method  of  manufacture,  being  affected 
by  both  the  amount  of  water  used  in  pugging  and  the  pressure  in  moulding. 
While  in  manufacturing  practice  the  amount  of  water  added  is  determined 
by  the  plasticity  of  the  clay,  investigations  have  shown  that  the  moisture 
content  should  be  about  8%  and  the  pressure  about  1500  Ibs.  per  square  inch 
to  secure  the  greatest  density. 


TESTING  REFRACTORIES  35 

The  Impact  Test:  This  test  is  important  in  the  case  of  brick  to  be 
used  in  blast  furnace  tops,  where  they  are  subject  to  much  impact  from 
lumps  of  ore,  stone,  and  coke  in  charging.  The  test  is  greatly  affected 
by  temperature.  A  brick  heated  to  260°C.  was  found  to  be  20%  weaker 
than  one  of  the  same  brand  tested  at  20 °C.,  and  40%  weaker  when  tested 
at  540 °C.  In  carrying  out  the  test,  the  brick  is  first  heated  from 
atmospheric  temperature  to  260 °C.,  the  temperature  being  raised  gradually 
through  a  period  of  one  hour.  The  brick  is  then  placed  end  up  in  a  machine, 
by  means  of  which  a  steel  ball  2l/2  inches  in  diameter  and  weighing  2.34 
Ibs.  is  dropped  upon  the  longest  axis  of  the  brick  from  heights  successively 
increasing  by  two  inches  until  the  brick  breaks.  The  height  in  inches  of  the 
ball  in  the  last  test  is  taken  as  the  measure  of  the  resistance  of  the  brick 
to  impact. 

The  Abrasion  Test :  This  test  aims  to  determine  the  wearing  qualities 
of 'the  brick  at  the  temperature  to  which  it  is  subjected  in  actual  service. 
The  brick  is  heated  to  the  required  temperature,  and  its  end  then  pressed 
against  a  carborundum  wheel  for  a  given  time  and  with  a  fixed  pressure. 
The  brick  must  be  ground  to  uniform  thickness  and  a  preliminary  cut  made, 
so  the  wheel  will  cut  through  the  entire  thickness  from  the  beginning  of 
the  test.  The  depth  of  the  cut  made  on  the  hot  brick  measures  the  abrasion. 
It  is  obvious  that  the  test  will  be  affected  by  the  width  of  the  cutting  wheel, 
the  speed  at  which  it  revolves,  also  the  grade  and  grit  of  the  carborundum, 
all  of  which  must  be  fixed  and  constant. 

Spalling  Test:  Spalling  in  a  brick  is  usually  produced  by  temperature 
changes,  often  accelerated  by  mechanical  pressure.  The  drawbacks  with  this 
test  are  the  fact  that  it  must  be  made  much  more  severe  than  the  conditions 
of  actual  service  and  that  it  concerns  the  brick  only  as  made,  thus  neglecting 
the  effect  of  slag  penetration  and  the  resulting  vitrification  that  often  causes 
brick  to  spall  in  service.  The  test  is  usually  made  on  several  bricks.  The 
bricks  are  dried  at  100°  C.  for  5  hours  or  more,  weighed,  and  then  placed  in 
the  door  of  a  furnace,  heated  to  1350°  C.,  so  that  one  end  only  is  exposed  to  the 
interior  heat  of  the  furnace.  The  remainder  of  the  door  space,  if  any,  is  then 
filled  with  other  brick.  After  heating  for  one  hour  at  this  temperature  the 
bricks  are  removed,  and  each  one  is  immediately  plunged  into  two  gallons 
of  water  at  20°  C.  to  a  depth  of  four  inches  and  held  there  for  three  minutes. 
It  is  then  withdrawn  from  the  water,  allowed  to  dry  three  minutes,  and  returned 
to  the  furnace  as  before.  This  operation  is  repeated  until  the  bricks  have 
been  plunged  ten  times,  when  they  are  dried  at  100°  C.  for  five  hours  or  more 
and  again  weighed.  The  percentage  of  loss  in  weight,  which  is  taken  as  a 
measure  of  the  spalling,  is  claculated  from  the  original  weight. 


36  IRON  ORES 


CHAPTER  III. 

IRON  ORES. 

SECTION   I. 

ORES   AND   THE   IRON   BEARING   MINERALS. 

Minerals  and  Ores:  Any  homogeneous  inorganic  substance  that 
occurs  naturally  in  the  solid  state  is  called  a  mineral.  A  mineral,  therefore, 
may  be  either  an  element  or  a  compound.  While  a  few  elements,  like 
gold  and  platinum,  occur  for  the  most  part  native,  and  others,  like  silver, 
copper,  mercury,  sulphur  and  carbon,  may  be  found  both  native  and  com- 
bined, most  minerals,  of  which  some  800  varieties  have  been  discovered 
and  named,  such  as  quartz,  feldspar,  hematite,  hornblende,  calcite,  mica, 
etc.,  or  their  species,  represent  definite  chemical  compounds.  Owing  to  the 
many  forces  that  are  constantly  at  work  in  nature  and  the  wide  distribution 
of  some  of  the  minerals,  it  is  seldom  a  deposit  consisting  of  but  a  single 
mineral  is  encountered.  It  is  of  such  natural  deposits  that  the  ores  are 
constituted.  In  general,  then,  an  ore  is  defined  as  a  mineral  or  a  mixture 
of  minerals  from  which  one  or  more  elements  may  be  extracted  with  profit. 

The  Iron  Bearing  Minerals:  While  there  is  a  vast  number  of  mineral 
species  that  contain  iron,  there  are  only  a  few  that  are  of  any  importance 
commercially,  because,  in  most  cases,  either  the  iron  content  is  too  low 
to  justify  the  extraction  of  the  metal  or  the  mineral  itself  does  not  occur  in 
sufficient  abundance  to  make  it  available  for  use  as  an  ore.  Grouped 
according  to  their  chemical  composition,  the  iron  bearing  minerals  of  chief 
importance  are  divided  into  four  classes;  namely,  the  iron  oxides,  iron 
carbonates,  iron  silicates,  and  iron  sulphides.  Of  these,  only  the  first 
class  may  be  considered  as  a  factor  in  the  manufacture  of  steel  in  the  United 
States.  These  oxides  go  to  form  a  large  number  of  minerals,  which  have 
been  grouped  and  named  as  shown  in  the  following  table: 

Table  4.     Chief  Iron  Bearing  Minerals. 

Chemical  Name  Mineralogical  Name. 

1.  Ferroso-ferric  Oxide Magnetite 

2.  Anhydrous  Ferric  Oxide Hematite 

3.  Hydrous  Ferric  Oxides Limonite  and  others 

4.  Ferrous  Carbonate Siderite 

5.  Iron  Silicates Chloropal  and  others 

6.  Iron  Sulphides Pyrite  and  others 


MINERALS  37 


Magnetite  Group:  The  only  important  mineral  of  this  group  is 
magnetite,  chemical  formula  Fe3O4,  composed  of  iron,  72.4%,  and  oxygen, 
27.6%.  The  mineral  is  found  in  Arkansas,  Pennsylvania,  New  Jersey,  and 
New  York.  It  varies  in  color  from  gray  to  black,  has  a  specific  gravity 
of  about  5.0,  and  is  magnetic.  This  last  named  property  is  taken  advantage 
of  in  locating  ore  bodies  below  the  surface  of  the  ground  and  in  mechanically 
purifying  ores  of  this  group  by  magnetic  concentration.  It  is  often  found 
closely  associated  with  igneous  rocks,  when  it  is  apt  to  contain  appreciable 
amounts  of  chromium  or  titanium  oxides  which  cannot  be  removed  from  it 
by  magnetic  concentration.  The  remaining  magnetic  ores  of  the  United 
States  are,  for  the  most  part,  of  a  low  grade  and  require  dressing,  but 
the  magnetite  ores  of  Sweden  represent  the  purest  ores  in  the  world  and 
are  of  a  grade  approaching  that  of  the  pure  mineral. 

Hematite  Group:  The  typical  mineral  of  this  group  is  hematite, 
which  contains  the  equivalent  of  70%  metallic  iron,  based  on  the  chemical 
formula  Fe2O3.  It  furnishes  the  base  of  the  world's  most  important  ores. 
Being  associated  with  rocks  of  various  geological  periods,  these  ores  occur 
widely  distributed,  and  in  a  variety  of  forms,  which  differ  greatly  in  their 
iron  content.  Many  of  these  varieties  are  known,  from  their  outstanding 
characteristic,  as  red  hematite,  specular  hematite,  oolitic  hematite,  fossil 
ore,  etc. 

Limonite  or  Brown  Ore  Group:  The  minerals  of  this  group  are  all 
hydrous  ferric  oxides,  and  may  be  represented,  as  a  group,  by  the  general 
formula  mFe2O3-  n  H2O.  There  are  five  of  these  minerals,  and  they  have 
been  named,  in  the  order  of  their  progressive  increase  in  water  content, 
turgite,  2Fe2O3-H2O;  goethite,  Fe2O3-H2O;  limonite,  2  Fe2O3-  3  H2O; 
xanthosidente,  Fe2O3-2  H2O;  and  limnite,  Fe2O3-  3  H2O.  On  a  theoretical 
basis  the  iron  content  of  this  series  will  vary  from  52.31%  to  66.31%. 
These  minerals  are  widely  distributed  throughout  the  United  States.  In 
southern  Virginia  they  make  up  the  greater  part  of  the  available  ores,  all 
of  which  are  low  in  iron  content  and  high  in  silica. 

The  Carbonate  Group:  The  representative  member  of  this  group  is 
the  mineral  known  as  siderite,  or  iron  carbonate,  FeCO3,  which  contains 
43.8%  of  iron.  Owing  to  the  fact  that  carbonic  acid  is  dibasic,  a  part  of 
the  iron  required  to  neutralize  it  may  be  replaced  by  other  metals,  thus 
giving  rise  to  a  series  of  minerals,  such  as  iron-calcium  carbonate,  iron- 
magnesium  carbonate,  etc.  Some  of  the  names  commonly  applied  to  these 
ores  are  spathic  iron  ore,  kidney  ore,  blackband  ore,  etc.  The  ore  deposits 
in  which  this  group  appears  are  of  little  commercial  importance  in  the 
United  States.  In  England  they  make  up  the  ores  of  the  Cleveland  district. 
Usually,  carbonate  ores  are  calcined  before  they  are  charged  into  the  blast 
furnace. 

The  Mineralogical  Make-up  of  Iron  Ores:  As  was  indicated  at  the 
beginning,  an  ore  deposit  at  best  represents  but  a  mixture  of  different 


38  IRON  ORES 


minerals,  only  a  part  of  which  will  contain  the  element  or  elements  sought. 
All  iron  ores,  then,  may  be  looked  upon  as  being  made  up  of  these  two 
parts:  One  part  is  composed  of  the  iron  bearing  minerals,  which  represent 
definite  compounds  of  iron;  the  other  part  includes  all  the  other  substances 
mixed  with  these  compounds,  and  is  known  as  the  gangue  of  the  ore. 
Evidently,  the  richness  of  the  ore,  by  which  term  is  meant  the  proportion 
by  weight  of  iron  to  all  other  elements  in  the  ore,  depends  on  the  composition 
of  the  iron  bearing  minerals  it  contains  and  upon  the  amount  of  gangue 
associated  with  them.  In  working  up  the  ores,  their  physical  condition 
must  also  be  taken  into  consideration.  In  this  respect,  they  are  subject 
to  the  widest  variation,  ranging  from  soft  clay-like  or  earthy  matter  to 
hard  compact  masses.  Both  extremes  tend  to  give  trouble  in  the  blast 
furnace.  Thus,  the  soft  fine  ores  are  so  apt  to  choke  up  a  furnace,  not 
designed  to  use  them,  that  they  were  once  considered  practically  worthless. 
The  successful  smelting  of  these  oreS  represents  one  of  the  great  achieve- 
ments of  American  furnacemen.  One  objection  to  very  fine  ores,  and  one 
that  has  not  yet  been  overcome,  is  that  they  give  rise  to  large  amounts 
of  flue  dust,  which  interferes  seriously  with  the  economical  utilization  of 
the  furnace  gases.  On  the  other  hand,  the  very  hard  and  dense  ores,  which 
enter  the  furnace  in  the  form  of  comparatively  large  lumps,  are  difficult 
to  reduce  and  require  an  excessive  amount  of  fuel. 


SECTION  II. 

VALUATION  OF  ORES. 

Factors  in  the  Valuation  of  Ores:  Omitting  relative  property 
valuations,  prices  of  competitive  ores,  costs  of  transportation,  and  other 
considerations  of  a  purely  business  nature,  the  chief  factors  that  determine 
the  value  of  an  ore  are  its  richness,  its  chemical  composition  and  its  access- 
ibility. The  richness  of  the  ore  will,  of  course,  be  made  the  basis  for  the 
valuation.  For  this  purpose  a  unit  system  is  employed,  a  unit  of  iron 
corresponding  to  one  per  cent.  But  the  prices  of  ores  do  not  rise  and  fall 
parallel  with  the  number  of  units  of  iron  they  contain,  because  the  gangue 
to  be  disposed  of  must  also  be  considered.  For  example,  suppose  two 
hematite  ores  containing  63%  and  42%  iron  are  being  considered.  In  the 
first,  90%  of  the  ore  is  pure  mineral,  leaving  only  10%  as  gangue  to  be 
disposed  of,  but  the  second  represents  only  60%  pure  mineral  with  40%  of 
its  weight  as  gangue  to  be  fluxed  and  transported.  Next  to  richness  comes 
the  consideration  of  the  chemical  composition  of  the  ore  as  a  whole,  for 
certain  impurities,  when  present  in  only  relatively  small  amounts,  may 
make  a  rich  ore  worthless.  Without  taking  the  time  to  consider  all  the 
possibilities  in  this  connection,  the  more  common  impurities  in  ore  may  be 
classed  as  follows: 


IMPURITIES  39 


1.  Those  impurities  that  are  never  reduced  in  the  blast  furnace 

and  so  do  not  affect  the  composition  of  the  iron  are  alumina,  AlgOsj  lime, 
CaO;  magnesia,  MgO;  and  the  alkalies,  soda,  (Na2O),  andpotassia,  (K2O). 
All  these  substances,  it  will  be  observed,  are  strong  bases,  with  the  exception 
of  alumina  which  may  be  either  an  acid  or  a  base.  Therefore,  the  presence 
of  these  substances  in  the  ore  may  not  be  objectionable,  for  the  lime  and 
the  magnesia,  in  particular,  are  valuable  as  fluxes.  Alumina,  also,  up  to 
about  5%,  may  play  a  useful  part  in  regulating  the  blast  furnace.  The 
alkalies  for  the  most  part  are  driven  off  with  the  flue  dust,  and  with 
modern  appliances  they  may  be  recovered,  when  present  in  sufficient 
amount  to  justify  the  installation  of  the  necessary  apparatus,  so  that  they 
may  form  a  valuable  by-product. 

2.  Those  impurities  that  may  be  partially  reduced  in  the  furnace 
and  give  elements  that  enter  the  p'ig  iron  are  silica,   or   the   silicates, 
sulphates  and  manganese  compounds.    Of  these,  the  silica,  which  term 
includes    both    the    free    silica   and    the   silicates,  constitutes    a    large 
part  of  the  gangue  of  most   ores,   and   as  it  requires   an  equal   weight 
of  lime  or  magnesia  to  flux  it,  it  must  be  considered  in  fixing  the  value  of 
an  ore.     Owing  to  the  fact  that  the  amount  reduced  in  the  blast  furnace 
is  subject  to  control  to  a  considerable  extent  and  that  the  element  is  readily 
removed  during  the  process  of  purifying  the  pig  iron,  it  is  not  considered 
of  much  importance  from  the  standpoint  of  its  effect  on  the  steel  produced 
from  the  iron.    This  attitude  toward  silica  is  just  the  opposite  of  that 
displayed  toward  the  sulphur  compounds.    All  these  compounds  are  reduced 
in  the  furnace  to  sulphides,  in  which  form  the  sulphur  enters  either  the 
metal  as  ferrous  or  manganese  sulphides  or  the  slag  as  calcium  sulphide. 
Now,  there  is  a  limit  to  the  quantity  of  sulphur  a  given  slag  can  absorb, 
the  highest  figures  given  being  less  than  5%,  and,  naturally  enough,  the 
nearer  this  limit  is  approached,  the  more  difficult  it  becomes  to  keep  the 
sulphur  out  of  the  metal.      Since  even  comparatively  small   amounts  of 
this   element  exert  an  evil  influence  in  steel,  and  it    can   be   removed 
from  the  metal  only  partially  and  with  much  difficulty,  the  importance 
of   this  element   in  fixing  the   value  of  an  ore   is  evident.    As  to  the 
manganese  compounds,  the  amount  of  this  element  that  enters  the  iron 
varies  with  the    manganese  content  of  the   ore  and  takes  place  to  the 
extent  of  nearly  75%  of  the  manganese  charged.      The  per  cent,  of  this 
element  is,  therefore,  considered  in  its  relation  to  the  iron  content.     An 
ore  is  available  for  the  manufacture  of  the  ordinary  grades  of  pig  iron 
when  the  manganese   content  does  not  exceed  2%  of  the  iron  content; 
between  2%  and  10%,  calculated  on  the  same  basis,  it  is  necessary  to 
mix  the  ore  with  others  containing  little  of  this  element;  but  if  the  manga- 
nese content  is  15%  to  20%  of  the  iron  content,  then  the  ore  becomes 
available  for  the  manufacture  of  spiegel. 


40  IRON  ORES 


3.  The  impurities  always  reduced  in  the  furnace  are  all  the  com- 
pounds of  phosphorus,  which  element  enters  the  pig  iron  only.  While 
this  element  is  easily  removed  from  the  metal  by  basic  processes,  none  at 
all  is  eliminated  by  the  acid  processes,  with  the  result  that  acid  steels 
contain  a  higher  percentage  of  this  element  than  the  average  of  the  charge 
from  which  the  steel  is  produced.  This  element,  therefore,  is  the  basis 
for  the  separation  of  all  ores  into  the  two  great  classes,  known  as  Bessemer 
and  basic.  This  division,  like  that  for  manganese,  is  made  on  the  basis 
of  the  relation  of  the  phosphorus  content  to  iron  content  of  the  ore.  Since 
it  is  desirable  to  produce  Bessemer  steel  that  will  contain  not  more  than 
.100%  of  its  weight  as  phosphorus,  a  true  Bessemer  ore  would  be  one 
whose  phosphorus  content  plus  the  phosphorus  content  of  the  coke  and 
limestone  required  to  smelt  and  flux  it  would  produce  a  pig  iron  with  a 
phosphorus  content  not  exceeding  .090%.  Allowing  10%  for  conversion 
loss,  such  a  pig  iron  would  give  a  steel  containing  less  than  .100%  of  its 
weight  of  phosphorus.  Commercially,  however,  since  commercial  toler- 
ances usually  permit  the  phosphorus  in  the  steel  to  rise  as  high  as  .110%, 
no  allowance  is  made  for  conversion,  and  a  commercial  Bessemer  ore  is 
one  whose  phosphorus  content  plus  some  arbitrary  figure,  usually  about 
.015%,  to  allow  for  the  phosphorus  acquired  from  the  flux  and  fuel,  is 
less  than  one  one-thousandth  of  its  iron  content.  Thus,  the  per  cent,  of 
phosphorus  in  an  ore  containing  60  units  of  iron  must  be  .045,  or  less,  to 
be  classed  as  a  Bessemer  ore,  for  1/1000  of  60=.060  and  .060— .015=. 045. 
Another  method  for  determining  the  grade  of  an  ore  is  explained  by  the 
following  example: 

Question*.  To  what  class  does  an  ore  containing  60%  iron  and  .045% 
phosphorus  belong? 

Solution: 

045-=-.60=.075=per  cent,  phosphorus  in  the  pig  iron,  acquired  from  the  ore. 
.020=Estimated  per  cent.  phos.  in  pig  iron,  acquired  from  coke 

and  stone. 

Ans.     .095=per  cent,  phosphorus  in  the  pig  iron.     Therefore;  the  ore  is 
of  Bessemer  grade. 


Water  or  moisture  is  another  factor  to  be  considered  in  the  valuation 
of  ores,  because  it  adds  to  the  weight  of  ore  to  be  handled  and  transported. 
The  importance  of  this  matter  in  fixing  the  value  of  an  ore  is  seen  at  once 
when  it  is  pointed  out  that  many  of  the  soft  ores  of  the  Lake  Superior  region 
carry  as  much  as  12%  of  their  weight  as  hygroscopic  water,  and  a  few  as 
much  as,  or  more  than,  15%.  This  moisture  content  for  any  particular  ore 
is  much  more  nearly  constant  under  varying  weather  conditions  than  might 
be  expected;  but  in  the  Case  of  different  ores  there  is  a  wide  variation, 
ranging  from  .40%  in  some  of  the  hard  red  hematites  to  16.80%  in  a  few 


IMPURITIES 


41 


of  the  soft  red  ores.  These  points  are  well  illustrated  by  the  table  below, 
the  examples  in  which  have  been  selected  because  they  show  about  the 
same  iron  content  when  dry. 


TABLE  5.    Analyses  of  Ores  Illustrating  Dry  and  Wet  Basis. 


£ 

Ai 

c« 

a 

8    * 

i 

•1 

02 

g 

2 

ORE 

STATE 

| 

8 

& 

1° 

f 

|3 

of 

i 

d    O 

M   M 

rl 

'a  o 

ra  O 

3mw 

$ 

^  JQ 

s 

^ 

a 

5'  ' 

feS 

s  m 

A.   (Marquette  Range)  .  . 

Dry  
Natural.  . 

57.36 
56.82 

.137 
.135 

15.62 
15.47 

.08 
.08 

1.26 
1.25 

.68 
.67 

.33 
.327 

.007 
.007 

.03 
.03 

.944 

B.   (Missabe  Range)  .... 

Dry  
Natural.  . 

57.03 
52.54 

.042 
.039 

12.48 
11.50 

.56 
.52 

1.69 
1.56 

.21 
.19 

.32 
.29 

.010 
.009 

2.80 
2.58 

7.87 

C.   (Missabe  Range)  .... 

Dry  
Natural.  . 

57.06 
47.47 

.081 
.067 

7.33 
6.09 

1.72 
1.43 

1.00 
.83 

.30 
.25 

.40 
.32 

.010 
.008 

2.00 
1.66 

16.80 

The  marketing  of  the  ores  and  all  the  metallurgical  calculations 
involving  them  are  based  on  the  analyses  of  samples  dried  at  100  °C.  It 
will  be  observed  that  drying  at  this  temperature  may  not  drive  off  water  of 
crystallization  and  that  in  the  case  of  the  brown  hematites  a  much  higher 
temperature  than  the  drying  temperature  is  required  to  drive  off  all  the 
combined  water. 


Accessibility;  It  is  evident  that  the  economic  importance  of  an 
ore  deposit  depends  to  a  great  extent  upon  its  size  and  its  location,  both 
geologic  and  geographic.  Thus,  an  ore  that  is  very  desirable  from  the 
standpoint  of  chemical  composition  and  physical  condition,  may  be  so 
located  as  to  be  practically  inaccessible;  or  granting  it  can  be  made  access- 
ible, the  amount  of  ore  in  the  deposit  may  not  justify  the  expense  of  opening 
it  up.  On  the  other  hand,  a  poor  ore  may  be  so  conveniently  located  that 
it  may  be  concentrated  at  a  profit.  A  thorough  discussion  of  this  topic 
cannot  be  undertaken  in  the  brief  space  allotted  to  this  chapter.  Suffice 
it  to  say,  that  the  working  of  any  ore  body  under  modern  conditions  presents 
difficult  engineering  problems  both  in  mining  and  in  transportation. 
Perhaps  the  best  way  to  impart  some  understanding  of  these  problems 
is  through  a  brief  description  of  the  ore  mining  operations  of  the  Steel 
Corporation,  itself.  With  the  exception  of  the  Tennessee  Coal,  Iron  & 
Railroad  Company,  which  obtains  its  ore  from  the  Birmingham  District 
in  Alabama,  all  the  constituent  companies  of  the  Corporation  depend 
upon  the  Lake  Superior  district  for  their  ore  supply. 


42  IRON  ORES 


SECTION   III. 

THE   BIRMINGHAM   DISTRICT. 

Location  and  General  Geology:  The  Birmingham  District  includes 
the  area  from  which  the  furnaces  at  Birmingham,  Ensley,  and  Bessemer 
secure  their  iron  ores,  and  is  co-extensive  with  Birmingham  Valley.  This 
Valley  extends  from  the  City  of  Birmingham  in  both  a  northeast  and  south- 
west direction  for  a  total  length  of  about  75  miles  and  a  width  of  about 
six  miles.  The  ore,  which  is  a  variety  of  red  hematite,  occurs  in  the  Clinton 
formation,  which  consists  of  shale,  sandstone,  iron  ore,  and  a  little  ferru- 
ginous limestone.  Geological  researches  conducted  by  the  government1 
indicate  that  the  ore  was  formed  at  the  same  time  as  the  rocks  with  which 
it  is  associated.  The  valley  lies  within  the  area  originally  covered  by 
this  formation,  which,  therefore,  occurs  on  both  sides  and  dips  away  from 
it  on  each.  But  it  is  only  in  Red  Mountain  that  the  ore  bed  has  been  found 
of  sufficient  thickness  and  purity  to  justify  its  being  worked  on  a  large 
scale,  and  nearly  all  of  the  most  productive  mines  are  located  in  a  section, 
about  62  miles  long,  of  this  mountain  between  Narrow  Gap  and  Sparks  Gap. 

Method  of  Mining:  All  of  the  red  ore  mines  in  the  Birmingham 
district  were  started  as  open  cuts  along  the  outcrop,  and  the  product  of 
these  surface  mines,  having  been  leached,  were  at  first  soft  ore.  At  a 
few  points  these  simple  mining  operations  are  still  carried  on,  but,  owing 
to  the  dip  of  the  ore  beds,  all  mines  from  which  any  large  quantity  of  ore 
has  been  taken  are  now  completely  underground  and  are  operated  by  means 
of  slopes  or  inclines.  At  these  greater  depths  the  ore  is  very  hard  and 
compact.  On  account  of  the  fact  that  the  southern  portion  of  the  ridge 
is  overlaid  by  more  recent  formations,  the  ore  gradually  becomes  more 
and  more  deeply  buried  on  passing  southward,  and  all  the  deepest  slopes 
are  in  the  strip  of  mountains  south-west  of  Birmingham.  The  deepest 
slope  at  this  southern  extremity  of  the  district  extends  downward  on  beds 
whose  average  dip  is  about  22°.  The  co-existance  of  the  ore  with 
limestone  and  the  proximity  of  coal  beds  suitable  for.  making  coke  give 
this  district  an  advantage  over  other  districts  of  the  country.  The  ore 
contains  phosphorus  to  the  extent  of  about  .8%,  which  is  much  higher 
than  other  basic  ores  of  the  country .f  By  employing  the  duplex  or  the 
triplex  processes  in  refining  the  pig  iron,  a  slag  with  a  high  phosphorus 
content  is  produced  that  is  available  as  fertilizer  for  agricultural  use. 

SECTION   IV. 

THE   LAKE   SUPERIOR   DISTRICT. 

Importance,  Location  and  General  Geology:  During  recent  years 
the  Lake  Superior  district  has  provided  approximately  four-fifths  of  the 
entire  iron  ore  output  of  the  United  States,  and  there  is  nothing  to  indicate 
but  that  the  region  will,  for  many  years  to  come,  continue  to  be  the  nation's 

i.  Sec.  Bulletin  U.  S.  Geol.  Survey  No.  315,  1907.  The  Clinton  or  Red  Ores  of 
the  Birmingham  District,  Alabama,  by  E.  P.  Burchard,  also  Bulletin  U.  S.  Geol. 
Survey  No.  340.  Investigations  relating  to  Iron  and  Manganese,  by  E.  F.  Burchard, 
A.  C.  Spencer,  W.  C.  Phalen. 


IRON  ORE  RANGES  43 


most  important  source  of  ore  supply.  This  district,  which  surrounds  Lake 
Superior,  contains  certain  isolated  areas,  or  ranges,  where  bodies  of  iron 
ore  have  been  discovered.  These  ranges  are  scattered  over  the  northern 
part  of  the  states  of  Michigan,  Wisconsin  and  Minnesota  and  also  a  part 
of  the  Canadian  province  of  Ontario.  Investigation  has  proven  that  these 
ore  bodies  occur  at  certain  well  defined  geological  horizons  and  are 
associated  with  certain  rocks.  Geologically,  the  Lake  Superior  deposits 
are  much  older  than  the  Clinton  ores  of  the  Birmingham  district,  being 
associated  with  rocks  of  pre-Cambrian  age.  According  to  the  conclusions 
of  those  who  have  made  a  study  of  the  area,  the  iron  was  originally  deposited 
as  an  integral  part  of  certain  sedimentary  rocks.  Following  their  deposi- 
tion and  solidification,  these  rocks  were  elevated  and  folded,  after  which 
surface  waters,  bearing  different  compounds  in  solution,  percolated  through 
them,  and,  through  chemical  action  and  solution,  concentrated  the  iron 
in  the  troughs  which  had  been  formed  by  the  folding  of  the  formation  or 
by  the  intrusive  dikes  which  had  cut  across  the  strata.  Much  later, 
with  the  retreat  of  the  ice  at  the  end  of  the  glacial  epoch,  these  ore 
bodies  were  left  covered  by  varying  depths  of  glacial  drift.  In  the  order 
in  which  they  were  opened  the  six  chief  areas,  or  ranges,  lying  within  the 
borders  of  the  United  States,  are  Marquette,  Menominee,  Gogebic, 
Vermilion,  Missabe,  and  Cuyuna. 

The  Marquette  Range  lies  near  the  southern  shore  of  the  lake  in  the 
state  of  Michigan,  and  a  short  distance  west  by  south  of  the  lake  city  of 
Marquette,  from  which  it  takes  its  name.  Besides  Marquette,  the  towns 
of  Ishpeming,  Negaunee,  Champion,  Republic  and  Gwinn  are  also  included 
within  the  area.  The  formation  is  narrow  as  compared  with  its  length 
and  very  irregular,  but  its  general  direction  is  from  east  to  west.  The 
original  outcrop  was  very  conspicuous  and  was  responsible  for  the  early 
discovery,  in  1844,  of  the  deposit,  which,  as  indicated  above,  was  the  first 
of  the  great  ranges  to  be  worked.  It  was  opened  in  1854,  and  up  to  1916  about 
119,292,000  long  tons  of  ore  had  been  taken  out  of  it.  The  shipments  for 
that  year  were  5,396,007  tons.  The  ore  is  partly  hematite  of  the  red,  soft 
variety,  but  there  are  smaller  amounts  of  magnetite  and  limonit'e  and  some 
hard  hematite. 

The  Menominee  Range  is  also  in  the  state  of  Michigan.  It  lies  several 
miles  due  south  of  the  Marquette  range  and  is,  hence,  nearer  Lake  Michigan 
than  Lake  Superior.  It  includes  the  towns  of  Iron  Mountain,  Vulcan, 
Norway,  Florence,  Alpha,  Crystal  Falls  and  Iron  River.  The  principal 
belt,  composed  mainly  of  hematite,  extends  in  a  direction  from  east  to 
west.  Only  a  part  of  the  range  is  productive,  but  up  to  1916  more  than 
103,600,000  long  tons  of  ore  had  been  mined  from  it,  and  during  that  year 
6,365,363  tons  were  shipped.  It  was  opened  in  1872. 

The  Qogebic  Range  lies  almost  due  west  of  the  Marquette  range,  and, 
extending  as  a  narrow  belt  in  a  direction  from  a  point  a  little  north  of  east 


14 


IRON  ORES 


IRON  ORES 


MAP 

OF  THE 

LAKE  SUPERIOR  REGION 

SHOWING 

IRON  RANGES 


46  IRON  ORE  RANGES 


to  a  point  a  little  south  of  west  of  its  center,  it  is  located  partly  in  Michigan 
and  partly  in  Wisconsin.  The  area  includes  the  towns  of  Hurley,  Ironwood 
and  Bessemer.  The  original  iron  formation,  which  dips  sharply  toward 
the  north,  rests  on  quartzite,  and  is  cut  by  igneous  dikes  that  extend  at 
almost  right  angles  to  the  original  quartzite.  The  dike  and  the  impervious 
strata  thus  combine  to  form  troughs,  in  which  ore  bodies  have  been  formed 
by  concentration.  The  ores,  which  are  mostly  soft  and  red,  represent 
partially  dehydrated  hematites,  with  subordinate  amounts  of  hard,  blue 
hematite.  The  range  was  opened  in  1884,  and  in  1916  there  had  been 
produced  from  it  more  than  94,812,800  long  tons  of  ore.  The  yearly  ship- 
ments for  1916  were  8,489,685  tons. 

The  Vermilion  Range  was  opened  the  same  year  as  the  Gogebic 
range.  It  lies  in  northeastern  Minnesota,  and  includes  the  towns  of  Tower, 
Soudan,  and  Ely.  The  whole  district  is  one  of  complex  folding,  so  the  ore 
deposits  occur  in  narrow  belts,  which  are  enclosed  on  the  bottom  and  sides 
by  original  greenstones  of  Archean  age  and  on  top  by  the  original  iron 
formation.  As  the  pitch  or  slope  is  very  steep,  the  outcrops  are  very  small. 
The  ores  are  all  hard  and  are  composed  of  red  and  blue  hematite.  This 
range  had  contributed  a  little  more  than  39, 526,800  long  tons  of  ore  by  1916. 
The  shipments  for  that  year  were  1,947,200.  This  range  and  the  three 
previously  mentioned  are  known  as  the  old  range*  to  distinguish  them 
from  the  more  recently  discovered  Missabe  and  Cuyuna  ranges. 

The  Missabe  Range  is  one  to  excite  the  interest  of  every  one  interested 
in  the  manufacture  of  iron  or  steel,  because  from  it  comes  the  greater  part 
of  the  ore  used  for  the  production  of  pig  iron  today.  It  was  opened  in 
1892  and  up  to  1916  about  406,855,200  long  tons  of  ore  had  been  taken  from 
its  mines.  The  shipments  for  the  year  were  42,526,612  tons.  It  lies  in 
Minnesota,  northwest  of  Lake  Superior,  and  extends  in  an  east  and  west 
direction  approximately  100  miles.  The  principal  towns  are  Biwabik, 
Eveleth,  Virginia,  Chisholm,  Hibbing,  Nashwauk,  and  Coleraine.  The 
iron  formation  is  the  Biwabik  in  the  Upper  Huronian.  It  lies  along  the 
southern  slope  of  a  ridge  that  is  known  as  the  Giants,  or  Missabe,  Range, 
and  has  a  gentle  slope  toward  the  south.  The  surface  is  covered  with 
glacial  drift,  and  rock  exposures  are  not  common.  This  surface,  originally 
covered  with  forest,  gave  few  signs  to  indicate  the  presence  of  ore  bodies. 
The  slope  of  the  iron  formation  is  gentle,  so  most  of  the  ore  deposits  are 
flat-lying  and  have  a  large  horizontal  area  compared  with  the  deposits  on 
the  other  ranges.  The  impervious  basement  under  the  ore  deposits  is 
formed  by  layers  of  slate  or  paint  rock,  interbedded  with  the  iron  formation. 
The  ores  are  mostly  soft  and  hydrated  hematites  and  limonite.  They  vary 
in  texture  from  very  fine  dust  to  fairly  coarse,  hard  and  granular  ore. 
Toward  the  western  end  of  the  district,  layers  of  sand  are  often  interbedded 
with  the  ore,  forming  the  so-called  "sandy"  ores,  which  require  concen- 
tration to  form  ore  of  commercial  grade.  The  deposits  are  all  compara- 
tively shallow. 


IRON  ORE  MINING  47 


The  Cuyuna  Range,  which  is  the  last  range  of  any  importance  to  be 
discovered,  was  opened  in  1911.  It  is  located  in  Crow  Wing  County,  Minne- 
sota, about  100  miles  west  of  Duluth.  The  principal  towns  in  the  district 
are  Deerwood,  Crosby,  and  Brainerd.  The  range  has  no  marked  topo- 
graphic features,  the  surface  being  level  and  covered  with  a  heavy  mantle 
of  sand.  Since  there  are  no  surface  indications  to  assist  in  the  exploration 
for  ore,  the  presence  of  lines  of  magnetic  variation  must  be  depended  upon 
almost  entirely.  By  drilling,  these  lines  have  been  found  to  be  associated 
with  belts  of  iron-bearing  formations  which  trend  in  a  northeasterly  and 
southwesterly  direction.  The  formation  is  interfoliated  with  slate  and 
schist,  and  is  usually  steeply  tilted.  At  some  localities  igneous  intrusive 
rocks  occur.  The  ore  deposits  are  usually  lenticular  in  form.  In  certain 
restricted  areas  of  the  range,  particularly  in  the  northern  part,  mangani- 
ferous  iron  ores  have  been  found.  The  deposits  of  these  ores  occur  in 
irregular  pockets  or  lenses,  and  contain  as  high  45%  manganese.  Some 
of  these  bodies  of  ore  are  being  worked  for  their  manganese  content  only. 
In  1916  the  yearly  production  had  reached  1,716,218  tons,  and  the  total 
production,  4,897, 298  tons. 

SECTION   V. 
MINING  THE  LAKE  ORES.1 

Prospecting  and  Exploration:  Since  the  Lake  Superior  ores  occur  in 
pockets  or  distinct  bodies  and  vary  much  as  to  character  and  location, 
the  actual  mining  of  the  ores  is  preceded  by  much  work  of  an  exploratory 
character.  This  work  includes  prospecting  and  exploration. 

Prospecting  is  the  term  generally  applied  to  the  quest  for  surface 
indications  of  ore,  or  the  conditions  which  would  warrant  the  expectation 
of  finding  ore  in  the  vicinity.  It  includes  such  quest  operations  as  geological 
examination,  dip  needle  work,  shallow  test-pitting,  and  trenching.  The 
ore  bodies  of  the  Missabe  Range  are  non-magnetic,  and  dip  needle  prospect- 
ing is  therefore  valueless.  On  the  Cuyuna  Range,  however,  magnetic 
attraction  as  evidenced  b'y  the  dip  needle  has  been  extensively  employed 
as  a  guide  to  the  location  of  ore  deposits;  in  other  localities  it  has  also 
found  limited  application. 

Drill  Exploration:  After  the  presence  of  an  ore  deposit  is  known  or 
suspected,  resort  is  generally  had  to  exploration  by  means  of  diamond  of 
churn  drills.  On  the  old  ranges  geological  conditions  generally  make  this 
manner  of  ascertaining  the  exact  limits  of  an  ore  deposit  impracticable; 
so,  if  two  or  three  adjacent  drill  holes  develop  considerable  depths  of  ore, 
the  sinking  of  a  shaft  for  underground  exploration,  development  and  mining 
is  generally  considered  warranted.  On  the  Missabe  Range,  however,  the 
flat-lying  and  comparatively  shallow  characteristics  of  the  ore  formation 
warrant  much  more  extensive  drill  explorations.  On  this  range,  then,  an 
ore  body  is  almost  invariably  followed  out  with  the  drills,  and  its  limits 

i  For  further  details  concerning  the  mining  of  the  Lake  Ores,  see  Minn.  School  of 
Mines  Experiment  Station  Bulletin  No.  1,  Iron  Mining  in  Minnesota,  by  Charles 
E.  Von  Barneveld,  University  of  Minnesota,  Minneapolis,  Minn. 


48 


IRON  ORES 


PIG.  4.     Open  Pit  Mining 


IRON  ORES 


FIG.  4.    Open  Pit  Mining 


50  IRON  ORE  MINING 


are  determined  to  the  point  where  the  complete  plan  of  development  can 
be  worked  out  in  advance  of  actual  mining  operations. 

Methods  of  Mining:  Both  open  pit  and  underground  methods  of 
mining  are  employed  in  the  mines  of  the  Lake  Superior  District.  On  the 
old  ranges,  where  the  ore  bodies  often  extend  to  great  depths  and  usually 
lie  at  angles  so  steeply  inclined  to  the  horizontal  that  the  surface  exposures, 
or  outcrops,  are  small,  underground  mining  methods  are  employed  almost 
without  exception.  On  the  Missabe  Range  the  ore  bodies  are,  as  a  rule, 
flatlying  with  relatively  large  areas  of  outcrop,  and  open  pit  mining  is, 
therefore,  general.  Of  course,  there  are  many  deposits  on  this  range  that, 
on  account  of  limited  operating  area,  excessive  depth  of  over-burden,  or  for 
other  reasons,  must  be  mined  by  underground  methods,  and  there  are, 
therefore,  a  large  number  of  underground  mines  also.  But  by  far  the 
greater  part  of  the  tonnage  produced  from  the  Missabe  Range  comes  from 
open  pits. 

Open  Pit  Mining:  Before  deciding  whether  an  ore  body  should  be 
mined  by  underground  methods  or  as  an  open  pit,  a  detailed  operating- 
analysis  is  made  of  the  proposition  to  determine  by  which  method  the  ore 
can  be  mined  most  economically.  Estimates  are  made  determining  the 
yardage  of  overburden,  or  "stripping",  that  must  be  removed  to  uncover  the 
ore  body,  the  tonnage  of  ore  which  can  then  be  mined  by  steamshovel,  and 
the  additional  tonnage  which  can  be  "scrammed"  or  "milled"  in  the  pit 
after  the  limits  of  steamshovel  operation  have  been  reached.  Then  the 
cost  of  the  entire  operation,  including  interest-charges  on  the  necessarily 
large  investment  in  stripping  removal,  is  calculated  and  reduced  to  a  final 
cost  per  ton  of  ore  recoverable.  If  this  figure  is  less  than  the  probable  cost 
per  ton  of  underground  mining,  and  if  the  other  operating  conditions  are 
satisfactory,  open  pit  operation  is,  of  course,  deemed  advisable.  The 
laying  out  of  an  open  pit  mine  involves  the  following  engineering  problems: 
first,  outlining  the  area  of  ore  which  it  will  pay  to  strip,!,  e.,  considering  the 
two  factors  of  depth  of  ore  and  thickness  of  overburden;  second,  planning  the 
disposal  of  stripping  which  it  will  be  necessary  to  remove  to  uncover  the  ore 
body,  for  this  material  must  often  be  hauled  considerable  distances  from  the 
pits  to  dump  grounds;  third,  locating  the  track  systems  outside  the  pit 
for  the  transportation  of  stripping  and  the  hauling  of  ore;  fourth,  designing 
the  system  of  railroad  tracks  within  the  pit  that  will  make  available  the 
maximum  quantity  of  ore  accessible  by  steamshovel,  which  designing 
generally  involves  a  series  of  switchbacks  on  limiting  operative  grades  and 
curvature;  fifth,  providing  for  drainings  of  the  pit;  and  sixth,  planning 
in  advance  for  the  mining  of  the  ore  that  cannot  be  mined  by  steam- 
shovel.  The  general  term  open  pit  mining  covers  three  recognized 
methods  of  mining,  i.  e.,  steamshovel,  milling  and  scramming.  Steam- 
shovel  mining,  of  course,  needs  no  description;  it  is  simply  the  loading 
of  ore  directly  into  railroad  cars  by  steamshovel. 


IRON  ORE  MINING 


51 


IRON  ORE  MINING 


Milling  is  a  term  applied  to  a  thoroughly  well  worked  out  system  of 
open  pit  mining,  extensively  prosecuted  in  the  early  days  and  still  applied 
under  suitable  conditions.  It  consists  of  the  following  operations:  first, 
the  removal  of  the  overburden  from  the  ore  body  to  be  mined,  this  being 
done  by  steamshovel;  second,  the  sinking  of  a  hoisting  shaft  or  incline  to 
the  bottom  of  the  ore  and  the  development  of  a  system  of  underground 


IRON  ORE  MINING  53 


tramming  drifts  tributary  to  the  shaft  and  underneath  the  ore  to  be 
mined;  third,  the  putting  up  of  a  number  of  raises  (vertical  openings) 
extending  from  the  underground  drifts  through  the  ore;  fourth,  "milling" 
or  shoveling  the  ore  into  the  raises,  through  which  it  is  drawn  into  tram 
cars  operating  in  haulage  drifts  that  lead  to  the  shaft  or  incline,  where  it  is 
hoisted  to  the  surface.  The  milling  system  of  mining  can  well  be  applied  to 
small  ore  bodies  which  can  be  successfully  stripped,  but  where  the  resultant 
open  pit  areas  are  too  small  to  permit  of  steamshovel  operation;  also,  as  a 
sequel  to  steamshovel  mining  in  larger  pits  where  considerable  depths  of 
ore  remain  after  the  limits  of  steamshovel  work  have  been  reached. 

Scramming  is  a  term  applied  colloquially  on  the  Missabe  Range  to 
the  operation  of  recovering  shallow  pockets  and  hummocks  of  ore  left 
unmined  in  and  around  the  open  pits  following  the  period  of  steamshovel 
mining.  It  is  a  general  term  inclusive  of  hand  work,  scraper  work,  mining 
with  dragline  excavators,  etc.,  and  is  applicable  generally  to  the  operation 
of  "cleaning  up"  a  pit  after  its  period  of  real  production  has  passed. 

Advantages  of  Open  Pit  Mining:  It  is  very  apparent  that  open  pit 
mining,  when  feasible,  offers  decided  advantages  as  compared  with  under- 
ground methods.  Probably  the  most  evident  of  these  is  the  possibility  of 
big  production;  in  1916  the  Hull  Rust  Mine  alone  shipped  7,665,611  tons  of 
ore, — more  than  10%  of  the  total  mined  in  the  United  States  during  that 
year,  which,  according  to  the  U.  S.  Geological  Survey,  amounted  to 
75,167,672  tons.  Where  the  overburden  is  light  in  comparison  with  the 
depth  of  ore,  and  stripping  charges  are  not  heavy,  open  pit  mining  produces 
low  cost  ore.  It  accomplishes  a  great  saving  in  labor;  the  output  per  man 
per  day  from  the  open  pit  mine  is  many  times  that  from  the  average 
underground  mine.  Aside  from  the  skilled  operators  of  the  steamshovels 
and  locomotives,  common  labor  only  is  required  in  open  pit  mining,  while 
in  underground  work  the  miner  is  a  rather  high  class  workman,  and  he 
receives  a  relatively  high  wage.  Owing  to  this  latter  condition,  strikes 
have  never  bsen  able  to  interfere  seriously,  so  far,  with  the  output  of 
Missabe  Range  open  pit  mines. 

Underground  Mining— Slicing:  The  system  of  underground  mining 
most  generally  in  use  in  the  mines  of  the  Missabe  Range,  and  in  the  soft-ore 
mines  of  the  old  ranges,  as  well,  is  known  as  top=slicing  and  caving.  The 
development  of  a  mine  under  this  method  is  as  follows :  First,  a  shaft  is  sunk 
to  the  bottom  of  the  ore  body,  or  to  such  depth  in  the  ore  as  has  been 
determined  as  desirable.  Second,  after  cutting  a  "station,"  pumproom 
and  pocket  at  the  bottom  of  the  shaft,  a  main  haulage  drift,  or  system 
of  haulage  drifts,  is  driven  out  underneath  the  ore  body.  Third,  raises  are 
put  up  from  the  haulage  drifts  at  intervals  of  about  50  feet  along  the  drifts 
through  the  ore  body  to  the  top  of  the  ore.  Fourth,  cross  cuts  are  driven 
from  the  tops  of  the  raises  to  the  limits  of  the  ore  body  or  the  property 
lines,  the  cross  cuts  being  parallel  and  the  same  distance  apart  as  the 


54 


IRON  ORE  MINING 


Fifth,  beginning  at  the  ends  of  the  cross  cuts  farthest  from  the 
raises,  the  ore  is  "sliced"  out  between  cross  cuts,  trammed  to  the  raises, 
dumped  into  the  latter,  drawn  off  thru  chutes  into  cars  operating  on  the 
main  haulage  level,  hauled  to  the  shaft,  dumped  into  the  shaft  pocket  and 
hoisted  to  the  surface,  where  it  is  either  loaded  direct  into  railroad  ore 


FIG.  7.     Underground  Ore  Mining — Square  Set  Timber. 


GRADING  55 


cars,  or  (if  in  the  Winter  time)  stockpiled  for  later  shipment.  A  "slice" 
consists  of  a  room  opened  up  between  crosscuts,  and  may  be  one,  two  or 
more  sets  wide  depending  on  the  tendency  of  the  overburden  to  crush  the 
temporary  timber  supports.  When  the  ore  has  been  removed  from  the  room 
or  slice,  the  supporting  timbers  are  blasted  out  and  the  overburden  allowed 
to  cave  and  fill  it.  Before  blasting  the  timbers,  however,  boards  are  laid 
over  the  floor  of  the  room  to  prevent  admixture  of  the  caved  material 
with  the  ore  below.  While  slicing  and  caving  operations  are  proceeding 
on  the  top  level,  the  cross  cuts  to  develop  the  next  level  immediately  below 
are  being  driven,  and  as  soon  as  considerable  areas  of  cave  have  been 
developed  on  the  first  level,  slicing  under  these  areas  is  started  on  the 
second  level.  Thus,  the  entire  ore  body  is  mined,  slice  by  slice,  and  level 
by  level.  Levels  are  generally  about  eleven  feet  apart,  floor  to  floor. 
Haulage  of  ore  on  main  levels  from  chutes  to  shaft  may  be  by  hand,  mule  or 
electric  motor,  depending  on  the  size  of  the  mine.  On  the  sub-levels  the 
ore  is  hand-trammed  in  small  dump  cars,  or  for  short  hauls,  in  wheelbarrows, 
from  the  slices  to  the  raises. 

Advantages  of  the  Slicing  System  of  Mining:  The  top-slicing-and- 
caving  system  has  many  advantages.  It  gives  a  high  percentage  of  ore 
extraction.  If  desired,  the  ore  from  different  working  places  can  be 
separated,  and  two  or  more  grades  can  be  produced  from  the  same  mine. 
Development  and  mining  operations  are  simple  and  safe,  and  can  be  carried 
out  along  well  defined  plans  worked  out  in  advance.  While  the  consumption 
of  mining  timber  is  high,  cheap  inferior  grades  are  used,  and  under  ordinary 
conditions  this  item  of  cost  is  not  excessive.  In  common  with  most  other 
systems  of  mining,  it  possesses  the  disadvantage  of  a  limited  number  of 
working  places;  considerable  handling  of  the  ore  is  also  necessary. 

The  depth  of  mine  shafts  on  the  Missabe  Range  rarely  exceeds  350 
feet.  The  average  is  probably  between  250  and  300  feet.  On  the  old  ranges, 
where  the  rock  formations  have  been  folded  and  tilted,  mining  operations 
extend  much  deeper.  Here  mine  shafts  500  to  1500  feet  deep  are  common, 
while  in  some  cases  mining  operations  are  still  in  ore  at  depths  well  in 
excess  of  2,000  feet. 

Grading  the  Ores:  In  the  early  days  of  iron  ore  mining,  no  grading 
of  the  ore  from  analysis,  such  as  prevails  today,  was  made,  and  the  ore 
was  known  by  the  name  of  the  mine  that  produced  it.  Then,  the  number 
of  mines  was  small,  and  the  ore  from  any  one  mine  was  fairly  uniform. 
As  the  production  increased,  however,  and  the  field  of  available  ore  was 
broadened  to  include  deposits  previously  regarded  as  unprofitable,  it 
became  necessary,  in  order  to  simplify  shipping,  to  grade  ores  according 
to  their  composition,  and,  further,  to  mix  ores  differing  in  composition  to 
produce  certain  grades.  Finally,  it  became  quite  common  for  one  mine 
to  ship  several  different  grades,  and  for  the  ore  from  several  mines  to 
be  grouped  under  one  name.  These  conditions  brought  about  a  necessity 


56  IRON  ORES 


for  knowing  the  exact  composition  of  the  various  ores,  and  whether  or  not, 
in  the  case  of  mixed  ore,  each  cargo  was  of  the  grade  guaranteed.  This 
grading  is  done  by  sampling  the  ore  in  the  cars  as  fast  as  they  are  loaded 
at  the  mine,  in  lots  not  exceeding  ten,  and  making  a  rapid  but  accurate 
analysis  for  the  determining  elements.  From  this  analysis  the  class  or 
grade  of  the  ore  is  fixed,  and  its  allotment  into  a  certain  group  can  be  made. 
This  is  the  work  of  the  grader,  who,  from  the  analysis  of  the  cars  as  sub- 
mitted to  him,  makes  a  theoretical  shipment  in  which  the  contents  in 
silica,  iron,  phosphorus  and  possibly  manganese,  the  determining  factors 
in  the  value  of  an  ore  for  its  particular  purpose,  must  fall  within  certain 
predetermined  limits. 

Transporting  the  Ores:  The  Lake  ores  now  supply  all  the  furnaces 
in  Western  New  York,  Western  Pennsylvania,  Ohio,  Illinois,  and  Indiana, 
as  well  as  those  in  the  ore  producing  states  of  Michigan,  Wisconsin,  and 
Minnesota.  In  order  to  reach  these  markets,  the  ores  must  be  transported 
for  distances  varying  from  300  to  more  than  1000  miles,  depending  upon 
the  locations  of  both  the  mine  and  the  furnaces.  The  cost  of  transporting 
this  ore  by  rail  alone  would  be  a  serious  handicap  to  some  furnaces,  but 
fortunately  the  chain  of  Great  Lakes  affords  a  cheap  mode  of  transportation 
for  the  greater  part  of  the  long  as  well  as  the  short  distances.  Nearly  all 
the  ore  mined  in  the  ranges,  then,  goes  first  by  rail  to  a  harbor  on  Lake 
Michigan  or  Lake  Superior,  where  it  is  loaded  on  ore  carrying  boats  that 
carry  it  either  down  Lake  Michigan  to  Chicago  or  Gary  or  through  Lake 
Huron  and  Lake  Erie  to  ports  further  south.  For  most  of  the  ore,  even 
these  lower  lake  ports  are  not  ultimate  destinations,  and  another  haul  by 
rail  is  required  to  place  it  at  the  furnaces.  Now,  to  return  to  the  grading 
of  the  ore,  what  was  there  referred  to  as  a  theoretical  shipment  might 
better  have  been  called  a  theoretical  cargo  or  boat  load.  When  the  cars 
containing  this  theoretical  cargo,  which  may  weigh  from  3000  to  13,600 
tons,  depending  upon  the  size  of  the  boat,  reach  the  dock  at  the  shipping 
port,  they  are  unloaded  into  the  dock  pockets,  one  on  top  of  the  other, 
three  to  six  cars  to  a  pocket,  in  such  order  as  to  mix  the  ore  as  much  as 
possible.  The  ore  is  then  allowed  to  flow  from  these  pockets  into  the 
hatches  of  the  steamer,  thus,  again  mixing  the  ore.  Then  the  boat 
proceeds  to  her  destination,  where  the  ore  is  unloaded  by  electrical, 
or  otherwise  operated,  grabs,  which  process  of  unloading  still  further 
tends  to  mix  the  ore  and  make  it  uniform.  All  this  mixing  of  the  ore 
is  not  to  be  thought  of  as  merely  incidental  to  the  operations,  but 
as  a  necessary  course  of  procedure,  for  uniformity  in  the  ore  is  a  very 
important  requirement  in  the  successful  operation  of  the  blast  furnaces.  If 
the  ore  is  unloaded  at  the  works  located  on  the  lakes,  it  is  sampled  for 
analysis  during  the  unloading  by  an  elaborate  system  -and  is  dumped 
upon  its  appropriate  stock  pile;  if  for  inland  works,  such  as  Pittsburgh, 
it  is  placed  in  cars  and  ultimately  reaches  the  works,  where  each  car  is 
sampled,  according  to  printed  instructions  common  to  all  the  works  of 


IRON  ORES  57 


the  Steel  Corporation.  The  cars  are  then  unloaded  upon  a  stock  pile  from 
which  the  ore  can  be  used  as  needed,  or  directly  into  the  furnace  bins, 
if  the  ore  is  needed  for  immediate  use. 

Mining  and  Grading  in  Winter:  In  winter  the  procedure  as  outlined 
above  has  to  be  changed  somewhat.  During  a  part  of  November,  and  all 
of  the  winter  months  of  December,  January,  February  and  March,  the  ore 
cannot  be  transported  over  the  lakes  because  of  the  ice.  On  this  account, 
operations  in  the  open  pit  mines  of  the  Missabe  District  are  suspended  in 
winter;  but  in  all  the  underground  works,  both  of  the  old  ranges  and  the 
Missabe,  mining  is  continuous  throughout  the  year,  and  the  ore  mined 
during  the  non-shipping  season  must  be  stock  piled.  As  this  ore  is  removed 
it  is  carefully  sampled,  and  average  samples  are  analyzed  daily.  These 
analyses,  supplemented  by  those  made  in  the  work  of  exploration  that  is 
constantly  carried  on  in  advance  of  the  mining,  make  it  possible  to  calculate 
the  average  composition  of  each  stock  pile  at  the  beginning  of  the  shipping 
season  in  the  spring.  This  stock,  therefore,  may  be  combined,  if  necessary, 
with  the  ore  direct  from  the  mines  to  make  up  cargoes  of  definite  and  known 
composition. 


58  FUELS 


CHAPTER  IV. 

FUELS. 

SECTION  I. 

SOME   PRE- REQUISITES   TO  THE    STUDY   OF  FUELS. 

'Introductory:  There  are  five  basic  materials  upon  which  the 
metallurgical  arts  depend;  namely,  ore,  fuel,  flux,  air  and  water.  Of 
these  one  is  as  important  as  the  other,  for  all  metallurgical  industry  would 
•cease  with  the  failure  of  any  one.  At  one  time  all  these  were  thought  to 
be  inexhaustible,  but  recently  it  has  been  generally  recognized  that  the 
supply  of  the  higher  grades  of  ore  are  limited,  and  that  the  more  suitable 
fuels,  at  the  present  rate  of  consumption,  must  be  exhausted  in  a  compara- 
tively short  time.  Representing  the  only  source  of  energy  under  man's 
absolute  control,  fuels  are  the  foundation  upon  which  a  nation's  progress 
and  prosperity  depends.  The  subject  is  also  a  very  large  one.  Hence,  in 
this  chapter  it  is  desirable  to  discuss  briefly  a  few  fundamental  topics  of 
general  interest,  and  more  in  detail,  a  few  matters  especially  important  in 
the  iron  and  steel  industry. 

Sensible  and  Specific  Heat:  Provided  no  change  of  state  is  involved, 
the  effect  produced  by  imparting  heat  to  a  body  is  a  rise  in  temperature 
of  the  body,  and  if  the  body  is  made  to  give  up  heat,  its  temperature  falls. 
This  heat,  which  is  easily  detected,  is  often  spoken  of  as  sensible  heat. 
The  quantity  of  heat  required  to  raise  the  temperature  of  a  body  1°C.  is 
called  its  thermal  capacity.  The  amount  of  heat  required  to  raise  the 
temperature  of  equal  masses  of  different  substances  1°C.  varies  greatly, 
and  the  thermal  capacity  of  one  gram  of  any  substance,  in  other  words, 
the  number  of  calories  required  to  raise  the  temperature  of  one  graml°C., 
is  called  its  specific  heat.  Specific  heats  are  determined  by  the  method 
of  mixtures,  which  is  based  on  the  law  of  heat  exchange.  This  law  states 
that  when  bodies  at  different  temperatures  are  brought  into  contact, 
exchange  of  heat  takes  place  until  a  uniform  temperature  for  all  is  reached, 
and  that  the  heat  lost  by  the  hotter  bodies  equals  in  quantity  that  gained 
by  the  colder  ones.  The  specific  heats  of  a  few  common  metals  follow: 
Iron=.109  cal.  Copper=.092  cal.  Zinc=.093  cal.  Mercury=.033  cal. 


HEAT  LAWS  59 


Latent  Heat  and  Change  of  State:     Changes  of  state  are  governed 
by  the  following  laws:1 
Laws  of  Fusion: 

I.  "Every  crystalline  substance  begins  to  melt  at  a  definite  temper- 
ture,  which  is  invariable  for  each  substance  if  the  pressure  is 
constant." 
II.  "The  temperature  of  a  body,  when  slowly  melting,  remains  constant 

till  the  whole  mass  is  melted." 
III.  "Substances  that  expand  on  solidifying  have  their  melting  points 

lowered  by  pressure,  and  vice  versa." 
Laws  of  Evaporation: 

I.  "The  rate  of  evaporation  increases  with  rise  of  temperature." 
II.  "The  rate  of  evaporation  increases  with  the  surface  of  the  liquid 
exposed."  . 

III.  "The  rate  of  evaporation  is  increased  by  a  continual  change  of 

air  in  contact  with  the  liquid." 

IV.  ''The  rate  of  evaporation  is  increased  by  diminishing  the  vapor  pres- 

sure, that  is,  by  applying  suction  to  the  vessel  inclosing  the  liquid" 
Laws  of  Ebullition: 
I.   "A  pure  liquid  has  a  definite  boiling  point,  which  is  invariable 

for  that  liquid  under  the  same  conditions." 

II.  The  temperature  of  the  vapor  given  off  by  a  pure  liquid  near  its 
surface  remains  constant  till  all  the  liquid  is  vaporized  if  the 
pressure  remains  constant. 

III.  "The  boiling  point  of  a  liquid  is  raised  by  salts  and  lowered  by 

gases  dissolved  in  it." 

IV.  "The  boiling  point  of  a  liquid  rises  with  increase  of  pressure  and 

falls  with  decrease  of  pressure." 

It  will  be  noted  from  these  laws  that  when  change  of  state  takes  place, 
there  is  no  change  in  temperature  of  the  body,  notwithstanding  the  constant 
application  or  withdrawal  of  heat.  The  heat  thus  involved  is  sometimes 
spoken  of  as  latent  heat,  though  heat  of  fusion  and  heat  of  vaporization 
would  appear  to  be  the  better  terms  to  employ.  The  heat  of  fusion  for  water 
is  about  80  calories  per  gram,  while  its  heat  of  vaporization  is  535.9  calories 
per  gram  under  standard  pressure. 

Transmission  of  Heat :  Heat  is  transmitted  in  three  ways;  namely,  by 
conduction,  by  convection  and  by  radiation.  Conduction  is  the  transmission 
of  heat  through  a  body  without  visible  motion  of  the  body,  as  through  an 
iron  bar.  When  the  heat  is  transmitted  by  mechanical  motion  of  the 
particles  of  matter,  through  air  or  water  currents  for  example,  it  is  called 
convection.  The  distribution  of  heat  through  a  blast  furnace  makes  use 
of  these  principles.  Radiation  refers  to  the  transmission  of  heat,  independ- 
ently of  matter,  by  means  of  waves  in  the  ether.  This  is  the  means  by 
which  the  heat  of  the  sun  reaches  the  earth.  These  factors  are  important  con- 
siderations  in  the  action  of  furnaces,  stacks,  ventilators  and  heating  plants. 
iSeeHigh  School  Physics  and  University  Physics  by  Henry  S.  Carhart  and  Horatio 
N.  Chute,  published  by  Allyn  and  Bacon,  Boston  and  Chicago. 


60  FUELS 


.Fuels  and  Combustion:  Any  chemical  reaction  by  which  light  and 
heat  are  evolved  is  called  combustion.  In  the  ordinary  cases  of  combustion, 
one  of  the  reacting  substances  is  the  oxygen  of  the  air.  Therefore,  fuels 
are  sometimes  defined  as  substances  which  will  burn  in  air  and  liberate 
heat  with  sufficient  rapidity  to  be  applied  to  practical  purposes.  The  chief 
elements  constituting  fuels  are  carbon  and  hydrogen,  though  in  certain 
processes  silicon,  phosphorus,  sulphur,  manganese  and  the  metals  may 
serve  as  fuel.  In  metallurgy  the  fuel  is  often  required  to  act  as  a  reducing 
agent,  in  which  cases  the  total  heat  produced  will  be  derived  from  two 
sources,  namely,  by  combustion  with  oxygen  of  the  air  and  by  combination 
with  oxygen  of  the  ore. 

Fuels  and  Chemical  Energy:  Fuels  represent  potential  energy, 
which  is  given  off  as  heat  by  chemical  action.  Therefore,  the  relations 
of  the  weights  of  fuel,  weights  of  air,  and  the  amounts  of  heat  evolved  are 
fixed  quantities.  The  following  reaction  furnishes  a  simple  illustration: 

C+O2=CO2+Heat, 

that  is,12  gm.C+32  gm.O2=44gm.CO2 +97200  cal.  (Heat  of  formation  of  CO2) 
orl  gm.C+2.666  gm.O2(11.51  gm.  air)=3.666  gm.CO2+8100  cal.  (Calorific 
power  of  carbon). 

The  heat  liberate  is  referred  to  in  two  ways.  The  chemist  bases  his 
calculations  on  the  total  heat  evolved  to  form  a  molecular  weight  in  grams 
of  a  given  substance,  in  this  case,  44  gms.  CO2,  which  is  called  the  heat 
of  formation  for  that  compound.  But  the  metallurgist  and  engineer 
employ  the  heat  evolved  from  a  unit  weight  of  fuel,  in  this  case,  one  gram 
of  carbon,  and  refer  to  it  as  the  calorific  power  of  tfce  fuel.  It  should  be 
observed  that  these  terms  take  into  consideration  only  the  total  amount 
of  heat  evolved,  irrespective  of  the  time  or  speed  of  the  reaction,  the 
duration  of  which  may  vary  through  wide  limits.  This  point  is  important 
in  the  attainment  of  high  temperatures  and  is  connected  with  the  second 
important  factor  affecting  the  combustion  of  fuels,  namely,  the  temperature 
to  which  the  products  of  combustion  may  be  raised  by  the  heat  evolved. 
This  is  referred  to  as  the  calorific  intensity  of  the  fuels.  Both  the  calorific 
power  and  the  intensity  enter  into  the  valuation  of  fuels. 

Measurement  of  Calorific  Power:  As  has  already  been  noted,  the  two 
practical  heat  units  are  the  large  calorie  and  the  B.  t.  u.  Metallurgists 
express  the  calorific  power  in  large  calories  per  kilogram,  which  is  numer- 
ically the  same  as  small  calories  per  gram  employed  by  chemists,  while 
engineers  use  B.  t.  u.  per  pound  of  fuel  as  the  basis  of  their  calculations. 
The  units  are  readily  converted  from  one  to  the  other;  the  relation  with 
respect  to  the  quantity  of  heat  they  contain  is  expressed  thus: 

B!  t.  u.  per  lb.:  Cal.  per  kilo=l  :  1.8 

Hence,  to  reduce  Cal.  per  kilo,  to  B.  t.  u.  per  pound,  it  is  only  necessary 
to  multiply  by  1.8.  The  factor  for  changing  B.  t.  u.  per  lb.  to  Cal.  per 
kilo  is  .5555. 


CALORIFIC  POWER  61 


The  Calorific  Power  of  some  common  elements  in  simple  oxidation 
reactions  is  as  follows:1 

Table  6.     Calorific  Power  of  Some  Elements. 

Element  Reaction.  Calorific  Power  in  Calories  per  Kilo. 

H  2H2+O2=2H2O  Liquid  34500 

H  2H2+O2=2H2O  Vapor  29030 

C  C+O2=CO2  8100 

C  2C+O2=2CO  2430 

Si  Si+  O2=SiO2  7000 

Al  4A1+3O2=2A12O3  7270 

P  4P+5O2=2P2O5  5895 

S  S+  O2=SO2  2196 

Fe  3Fe+2O2=Fe3O4  1612 

N  N2+  O2=2NO  —1541 

Calculating  Calorific  Power:  Given  the  heats  of  formation  of  the 
reacting  substances  and  of  the  products  of  combustion,  it  is  possible  to 
calculate  the  calorific  power  of  some  fuels  from  their  analyses.  The  calorific 
power  of  a  well  made  coke  can  be  estimated  approximately  from  the  fixed 
carbon,  if  the  moisture  and  volatile  matter  are  low. 

By  analysis,  Fixed  Carbon=87.0% 

Calorific  Power  of  Carbon=8100  Cal.  per  Kilo 

.87 


7047  Cal.  per  kilo.=calorific  power  of  coke 

This  calculation  for  gases  becomes  more  complicated,  because  the 
calorific  power  is  usually  expressed  in  Calories  per  cubic  meter  or  B.  t.  u. 
per  cu.  ft.  This  fact  requires  a  conversion  from  weight  to  volume,  since 
the  calorific  powers  in  the  table  are  based  on  weight.  This  conversion, 
however,  is  a  simple  matter,  since  a  gram  molecular  weight  of  any  gas  has 
a  volume  of  22.32  liters  under  standard  conditions.  To  find  the  heat  evolved 
from  a  gas  in  calories  per  liter,  it  is  only  necessary  tocdivide  the  heat  of 
formation  by  22.32.  In  the  case  of  a  blast  furnace  gas  composed  of  CH4, 
.2%;  CO,  25%;  H2,  3%;  CO2,  12%;  N2,  59.8%;  the  calorific  power  may  be 
found  as  follows:  The  reactions  that  may  occur  in  complete  combustion 
are 

Reaction  (1)  CH4+2O2=2H2O+CO2 

Heats  of  formation,  21700  cal. +0=2x58060  cal.  +97200  cal. 

Reaction  (2)  2CO+O2=2  CO2 

Heats  of  formation,  2x29160  cal. +0=2x97200  cal. 

Reaction  (3)  2H2+O2=2H2O 
Heats    of     formation,  2x58060  cal. 

iSee    Metallurgical  Calculations  by  Joseph  W.  Richards,  One  Volume  Edition 
published  by  McGraw-Hill  Book  Company,  New  York. 


62  FUELS 


From  reaction  (1)  the  total  heat  available  from  CH4= 

per  litel, 


22.32 

From  (2)  available  heat  from  CO= 

972^0—  29160==3048+calories  per  liter> 
22.32 

From  (3)  available  heat  from  H2= 

H5?15_=2605.+calories  per  liter. 
2x22.32 

Total  heat  of  gas  available  is, 
for  CH4  .2%  of  8585=  17.17 
CO    25%  of  3048=762.00 
H2    3%  of  2605=  78.16 


857.33  calories  per  liter  at  0°C.  and760m.m. 
pressure= (857.33 x.l  1236)  =96.33— B.  t.  u.  per  cu.  ft. 

Practical  Tests :  All  calculated  results,  however,  are  usually  higher 
than  can  be  obtained  in  actual  practice.  Furthermore,  with  complex  fuels, 
like  coals,  the  composition  of  which  can  only  be  guessed  at,  it  is  impossible 
to  make  accurate  calculations  from  the  analysis,  because  no  account  is 
taken  of  the  heat  required  to  decompose  the  fuel  and  gasify  the  products. 
Many  fuel  chemists,  however,  have  evolved  formulas  by  which  they  are 
able  to  determine  very  closely  from  the  analysis  the  calorific  value  of  a 
coal  as  obtained  by  laboratory  experiment.  Nevertheless,  experimental 
methods  are  relied  upon  almost  wholly  to  determine  the  heating  power 
of  fuels.  These  tests  may  be  practical,  in  which  large  quantities  of  the 
fuel  are  consumed  under  conditions  approximating  closely  those  of  the 
process  for  which  the  fuel  is  to  be  used;  or  they  may  be  laboratory  tests, 
in  which  small .  quantities  of  fuel  are  burned,  and  the  heat  evolved  is 
measured.  Practical  tests  may  be  made  in  specially  constructed  apparatus 
or  under  boilers  in  actual  service.  These  specially  constructed  apparatus 
are  in  the  form  of  large  heaters  through  which  water  circulates  and  in  which 
the  fuel  may  be  completely  consumed.  From  the  amount  of  fuel  consumed, 
the  weight  of  water  heated,  the  rise  in  temperature  of  the  water,  the 
difference  in  temperature  between  the  in-going  air  and  the  products  of 
combustion,  the  calorific  power  may  be  accurately  determined. 

Laboratory  Tests :  For  determining  the  maximum  amount  of  heat  a 
given  fuel  is  capable  of  generating,  laboratory  tests  are  more  exact  than 
practical  tests.  Such  tests  are  carried  out  in  specially  designed  apparatus 
called  calorimeters.  There  are  several  makes  of  these  instruments,  but 


CONSERVATION  OF  HEAT.  63 

the  fundamental  principles  of  all  are  the  same.  The  process  consists  in 
completely  oxidizing  the  fuel  in  a  space  enclosed  by  a  metal  jacket  (the 
bomb)  so  submerged  that  the  heat  evolved  is  absorbed  by  a  weighed 
portion  of  water  contained  in  a  perfectly  insulated  vessel.  From  the  rise 
in  temperature  of  the  water,  the  heat  liberated  by  one  gram  of  the  fuel  is 
calculated.  The  best  types  of  calorimeters  are  those  called  oxygen  bomb 
calorimeters,  in  which  the  fuel  is  burned  in  the  presence  of  compressed 
oxygen. 

Calorific  Intensity:  The  calorific  intensity  is  more  precisely  defined 
as  the  degree  of  heat  evolved  by  a  given  weight  of  fuel  in  perfect  combustion 
in  air  at  0°C.  and  760  m.  m.  pressure.  The  theoretical  maximum  temper- 
ature depends  on  the  calorific  power,  and  the  density  and  specific  heats  of  the 
products  of  combustion,  and  is  inversely  proportional  to  the  time  required 
in  producing  it.  In  practice  the  temperature  is  also  affected  by  the  initial 
temperature  of  the  fuel  and  air,  the  amount  of  air  used,  amount  of  water 
in  fuel  and  air,  and  by  radiation,  conduction  and  convection  of  materials 
of  the  furnace.  As  the  attainment  of  high  temperatures  is  necessary  to 
many  metallurgical  processes,  all  these  factors  are  important,  and  special 
devices  have  been  invented  to  prevent  waste,  preheat  air'  and  gas,  and 
eliminate  moisture. 

Methods  of  Conserving  Heat:  Owing  to  the  high  temperature  at 
which  the  products  of  combustion  escape  from  furnaces  and  the  large  volume 
of  air  necessary  for  the  combustion  of  the  great  quantities  of  fuel  used, 
much  of  the  heat  generated  in  the  furnace  is  carried  away  by  the  outgoing 
gases  and  wasted,  unless  special  methods  are  employed  to  recover  this  waste. 
This  can  be  done  in  several  ways.  The  hot  gases  may  be  passed  through 
boilers  and  made  to  generate  steam,  conducted  into  other  furnaces  requiring 
lower  temperatures,  or  used  to  preheat  the  air  and  fuel  and  thus  increase 
the  intensity  of  the  heat  in  the  furnace.  Since  high  temperatures  are 
required  in  most  metallurgical  processes,  the  third  option  is  generally 
selected.  The  methods  by  which  this  preheating  is  accomplished  depends 
upon  two  principles,  called  the  regenerative  and  the  recuperative.  In 
the  regenerative  method  the  hot  gases  from  the  furnace  are  conducted 
through  expanded  portions  of  the  horizontal  flues,  almost  filled  with  open 
brick  work,  called  the  "checkers"  from  the  manner  of  laying  the  bricks. 
When  the  checkers  have  absorbed  heat  sufficient  to  raise  their  temperature 
to  nearly  that  of  the  gases,  their  connection  with  the  stack  is  closed,  and 
the  air,  or  air  and  fuel,  if  the  latter  can  be  preheated,  is  made  to  pass  through 
the  checkers  on  its  way  into  the  furnace,  thus  taking  on  the  stored  up  heat  in 
the  checkers.  With  two  such  sets  of  checkers  to  a  furnace  this  process  is 
made  practically  continuous  by  reversing  the  direction  of  the  gases  at  short 
intervals.  In  the  recuperative  method  the  checkers  are  replaced  by  a 


64  FUELS 


system  of  pipes  through  which  the  out-going  gases  must  pass.  The  in-going 
air,  being  at  the  same  time  drawn  in  through  the  space  around  the  pipes, 
is  heated  in  proportion  as  the  waste  gas  is  cooled. 

Pyrometers:  The  measurement  of  high  temperatures  requires  special 
instruments  called  pyrometers,  many  of  which  are  made  self  recording  so  as  to 
measure  continuously  the  temperature  of  a  furnace  through  long  periods  of 
time.  There  are  many  types  of  these  instruments,  and  only  the  principles 
upon  which  some  of  the  more  important  types  are  based  will  be  briefly 
described. 

Specific  Heat,  or  Water,  Pyrometer :  This  is  an  old  type  of  instrument, 
and  one  that  is  still  extensively  used.  The  operation  of  the  instrument  is 
carried  out  as  follows:  A  weighed  amount  of  metal  of  known  specific  heat 
is  placed  in  a  furnace,  and  when  it  has  attained  the  temperature  of  the 
furnace,  it  is  withdrawn  and  quickly  dropped  into  an  insulated  vessel,  con- 
taining a  definite  amount  of  water  and  provided  with  a  thermometer  for 
reading  the  temperature  of  the  water.  The  rise  in  temperature  of  the 
water  is  proportional  to  the  weight  of  the  ball,  its  specific  heat,  and  the 
temperature  of  the  furnace.  The  first  two  factors  being  known,  the 
temperature  of  the  furnace  can  be  readily  calculated. 

Electric  Resistance  Pyrometers :  Instruments  of  this  type  depend  on 
the  fact  that  the  electrical  resistance  of  metals  increases  with  rise  in  their 
temperatures.  In  practice  the  metal  will  be  platinum  in  the  form  of  wire, 
which  will  be  inserted  in  one  arm  of  a  wheatstone  bridge  for  measuring 
resistance.  A  battery  and  a  galvanometer  for  detecting  difference  in 
potential,  both  being  attached  to  the  bridge,  completes  the  apparatus.  In 
operating  the  instrument,  the  slide  on  the  bridge  is  adjusted  so  that  the 
resistance  of  the  two  arms  of  the  bridge  are  the  same  and  the  galvanometer 
reading  is  zero.  The  "bulb"  of  platinum  wire  is  now  inserted  in  the  furnace, 
when,  the  resistance  of  the  platinum  wire  being  increased  by  the  rise  in 
temperature,  it  is  necessary  to  insert  resistance  in  the  other  arm  of  the 
bridge  to  keep  the  galvanometer  reading  at  zero.  The  amount  of  the 
resistance  inserted  measures  the  increase  in  resistance  of  the  wire,  which 
can  be  interpreted  in  degrees  of  temperature. 

Thermo-Electric  Pyrometers:  These  instruments  are  both  con- 
venient and  accurate,  being  very  simple  in  construction.  They  depend 
upon  the  fact  that  if  two  metals  are  in  contact  at  a  given  point,  any  change 
in  temperature  at  that  point  causes  an  electric  current,  the  intensity  of 
which  is  proportional  to  the  change  in  temperature,  to  flow  around  a  circuit 
connecting  their  free  ends.  This  current  can  be  measured  by  inserting  a 
millevolt  meter  in  the  circuit.  In  practice  the  metals  employed  for  high 
temperatures  are  platinum  in  conjunction  with  an  alloy  of  platinum  and  10% 


PYROMETERS  65 


rhodium  or  iridium  in  the  form  of  wires,  which  are  insulated  from  each  other 
by  means  of  hollow  tubes  of  refractory  materials.  For  low  temperatures  the 
baser  metals  may  be  used,  such  as  iron  and  nickel-copper  alloys. 


Hot 


Platinum 


Junction  /"  Voltmeter 

Pt.  +  10%  Iridium 

FIG.  8.     Diagram  of  Wiring  for  Thermo-Electric  Pyrometers 


Radiation  Pyrometers  are  based  on  the  law  of  heat  radiation  which 
is  briefly  stated  thus:  The  energy  emitted  by  a  highly  heated  black  body 
is  proportional  to  the  fourth  power  of  its  absolute  temperature.  Such 
instruments  consist  of  a  millevoltmeter  and  a  telescope  which  contains  a 
concave  mirror  reflector  and  a  delicate  thermo  electric  couple.  By  pointing 
the  telescope,  from  a  certain  distance,  toward  a  highly  heated  surface,  a 
portion  of  the  radiant  heat  is  made  to  fall  upon  the  mirror,  which  con- 
centrates the  rays  upon  the  couple,  causing  it  to  generate  a  current  that 
can  be  measured  by  the  millevolt  meter. 

Optical  Pyrometers  depend  upon  the  relation  of  the  intensity  of  light 
emitted  by  an  incandescent  body  and  its  temperature.  In  them  the 
intensity  of  the  light  from  the  hot  body  is  compared  with  that  of  an  incan- 
descent lamp.  The  simplest  form  consists  of  a  telescope  containing  the 
lamp  and  a  battery  to  supply  the  current.  In  making  a  determination, 
the  telescope  is  pointed  at  the  heated  body,  and  the  current  is  adjusted 
so  that  the  intensity  of  light  from  the  filament  of  the  lamp  matches  that 
from  the  body.  From  the  adjustment  necessary  the  temperature  of  the 
body  is  determined.  In  improved  forms  of  this  instrument,  a  circular  plate 
of  colored  glass  is  inserted  in  the  telescope  between  the  lamp  and  the  eye 
in  such  a  manner  that  the  light  from  the  lamp  falls  on  one-half  of  this  plate 
and  light  from  the  body  falls  on  the  other.  The  two  lights  are  matched 
by  varying  the  intensity  of  the  light  from  the  body  with  a  diaphragm.  A 
second  improvement  is  made  by  providing  a  special  rotating  prism  by  means 
of  which  the  lights  from  both  the  body  and  the  lamp  are  varied  in  intensity. 
The  amount  and  direction  of  rotation  necessary  to  match  the  lights  measures 
the  temperature. 

All  modern  pyrometers  are  constructed  with  graduated  scales  to  read 
in  degrees,  so  that  no  calculations  for  converting  the  various  relations  into 
temperatures  are  required. 


66 


FUELS 


SECTION   II. 

CLASSIFICATION  OF   FUELS. 


Of  the  many  ways  of  classifying  fuels,  that  shown  below  in  Table  7 
is  a  very  logical  and  simple  one  and  most  convenient  for  the  purposes  of 
this  chanter.  It  requires  no  explanation. 


Table  7.     Classification  of  Fuels. 

,  (Hard. 
Wood 


Carbon- 
Hydrogen 
Fuels 


Natural 


Peat 


Soft. 

New. 


lOld. 


Lignite 


New. 


Liquid 


I-PJ.,       .         /Coking. 
^     ,    Bituminous  <  ... 
CoaH  \Non-coking. 

[Anthracite. 


f  Briquettes. 
Prepared  <{  Pulverized  Coal,    f  Charcoal. 

[  Carbonized  Fuel  {  ~  .    /Beehive. 
v_yOke\  -p.  , 

\  (By-product. 

Natural — Petroleum . 


Prepared 


Gaseous 


Distilled  Oils. 
Coal  Tar. 


Natural— Natural  Gas. 

(Producer  Gas. 
Blast  Furnace  Gas. 
Coke  Oven  Gas. 
[Coal  Gas. 


Incidental 
Fuels 


Bessemer  Converter 


Silicon. 
Phosphorus. 

Sulphur  Works<f^°astinS- 
Smelting. 


Iron. 

Manganese. 
Carbon. 


LIQUID  FUELS  67 


Plan  of  Study:  In  discussing  the  different  fuels  it  does  not  seem 
desirable  to  follow  the  order  of  the  outline  above.  Some,  like  blast  furnace 
and  coke  oven  gases,  are  best  taken  up  in  connection  with  the  processes 
that  produce  them,  while  others,  like  the  distilled  oils,  are  of  so  little 
importance  from  a  metallurgical  standpoint  that  they  cannot  be  more  than 
mentioned  here.  Concerning  the  others,  which  play  more  or  less  prominent 
parts  in  metallurgical  processes,  it  is  the  intention  to  dispose  very  briefly 
of  the  less  important  first,  so  that  the  attention  may  be  concentrated  upon 
the  more  important  ones,  which  will  be  taken  up  at  the  last. 


SECTION   III. 

INCIDENTAL  AND    LIQUID   FUELS. 

Incidental  Fuels:  Under  this  heading  is  included  all  substances 
which  incidentally  act  as  fuels  in  certain  processes.  In  the  acid  Bessemer 
converter,  for  example,  the  oxidation  of  the  impurities,  silicon,  manganese 
and  carbon,  to  which  is  added  phosphorus  and  sulphur  in  the  basic  converter, 
furnish  heat  necessary  to  keep  the  metal  in  a  molten  state  during  the  blow, 
and  so  perform  the  function  of  fuels.  In  the  roasting  and  smelting  of  pyritic 
ores  the  burning  of  a  portion  of  the  sulphur  furnishes  a  great  part  of  the 
heat  necessary  for  those  processes. 

Tar:  The  use  of  tar  as  a  fuel  is  of  recent  origin,  and  offers  a  means 
for  the  disposal  of  the  excess  quantities  produced  above  that  required  by 
the  tar  refiners.  Having  a  low  ash  and  sulphur  content,  it  is  well  suited 
chemically  for  use  as  open  hearth  and  heating-furnace  fuel.  It  is  a  viscous 
fluid  at  ordinary  temperatures.  Hence,  it  must  be  kept  at  a  relatively 
high  temperature  both  in  the  storage  tanks  and  feed  lines.  This  heating 
is  accomplished  by  means  of  steam  pipes  immersed  in  the  tar.  Special 
burners,  one  type  of  which  is  shown  in  the  accompanying  figure,  of  the 
steam  or  air  injector  type  are  required  to  burn  tar  properly.  Tar  carries 
in  suspension  a  great  many  small  carbonaceous  bodies,  and  on  standing, 
especially  at  the  lower  temperatures  prevailing  in  storage  tanks,  these 
grow  into  pitch-like  bodies  of  considerable  size,  which  clog  up  the  burners 
and  the  small  pipe  lines  of  the  system.  Its  calorific  power  is  between  that 
of  coal  and  oil,  16000—18000  B.  t.  u.  per  pound.  This  fact,  coupled  with 
its  low  cost  due  to  the  increased  production,  tends  to  stimulate  efforts  to 
use  it  wherever  possible. 


68  FUELS 


Tar/ 
ijl 

Air 

FIG.  9.    One  Type  of  Tar  Burner. 

Petroleum:  The  only  natural  liquid  fuel,  and  a  material  of  the  highest 
commercial  importance,  is  petroleum,  a  product  obtained  from  reservoirs 
deep  in  the  earth.  Its  heating  power  is  much  greater  than  that  of  coal, 
(The  calorific  power  of  crude  petroleum=21000  B.  t.  u.  per  pound,  Coal= 
9000  to  15000  B.  t.  u.  per  pound)  and  it  is  obtained  in  immense  quantities. 
On  distilling,  it  yields  a  high  percentage  of  very  valuable  oils.  On  this 
account  it  is  used  as  a  metallurgical  fuel  only  where  coal  is  scarce  and 
high  in  price.  In  using  the  oil  special  burners  are  required,  as  it  must  be 
vaporized  or  atomized  and  properly  mixed  with  air  to  insure  complete 
combustion. 

Composition  of  Petroleum:  Petroleum  is  a  very  complex  mixture 
of  organic  compounds.  In  small  amounts  it  contains  compounds  of  oxygen, 
sulphur,  and  nitrogen,  but  principally  it  is  composed  of  compounds  of  car- 
bon and  hydrogen.  Its  content  of  the  former  element  varies  from  84  to 
87%,  and  of  the  latter,  from  11  to  13%,  depending  upon  the  locality  from 
which  it  is  obtained. 

Hydrocarbons — Generalized,  Empirical  and  Structural  Formulas: 

These  compounds  of  carbon  and  hydrogen  found  in  petroleum  are  called 
hydrocarbons.  They  are  numbered  by  the  hundred,  and  a  study  of  their 
composition  has  shown  that  they  fall  into  a  number  of  homologous  series 
which  may  be  represented  by  generalized  formulas  as  shown  in  Table  8. 
In  representing  these  compounds,  the  empirical,  or  simplest,  formulas  are 
often  found  inadequate,  because  it  frequently  happens  that  two  different 
compounds  will  have  the  same  empirical  formula,  and  that  in  many  com- 
pounds the  valence  of  carbon  is  apparently  not  a  whole  number.  To 
overcome  this  defect,  the  structural  formula,  which  aims  to  show  how  the 
molecules  are  built  up,  was  invented.  In  these  formulas  the  valence  of 
carbon,  which  is  represented  by  — 's,  called  valence  bonds,  is  assumed  to 
be  four  in  all  cases,  and  it  is  also  assumed  that  the  atoms  of  carbon  have 
the  power  of  uniting  with  each  other  to  form  nuclei  to  which  other 
elements  may  attach  themselves.  These  formulas  are  also  illustrated  in 
the  following  table: 


PETROLEUM 


69 


Table  8.    The  Different  Homologous  Series  of  Hydrocarbons. 


Generalized 
Formula  of 
Series 

Names  Applied 
To  Series 

Names  of  First 
Compound  of  Series 

Empiri- 
cal 
Formula 

Structural 
Formula 

Formula  of 
Second 
Member 

CnH2n+2  ..  . 

Methane,  Paraffin, 
or  Chain  Series. 

(  Methane 
•{  Marsh  Gas 
(Fire  Damp 

CH4 

H 
H-C-H 

A 

H    H 
H-C—  C-H 
H     h 

CnH  2n  

Oleflne,    Ethylene, 
Unsaturated  Open 
Chain  Series. 

Ethylene. 

C2H4 

H    H 

TT      TT 

H    H 
C=C 
H     CH8 

CnH2n-2.... 

Acetylene  Series. 

Acetylene. 

C2H2 

H-CsC-^H 

H-C=C-CH8 

CnH2n-4  

First  member  unk 

nown. 

CnH2n-6  

Benzene,  - 
Aromatic  or 
Closed  Ring  Series. 

Benzene. 

CeH6 

H 

6 

H—  C     C—  H 
H-C     C-H 

V 

H 

6 
/    \ 
H-C      C-H 

H-C      C-CH 

* 

CnH2n-8  

Not  many  membe 

rs  discovered. 

CnH2n-io..  . 

Not  many  membe 

rs  discovered. 

So  on  to  

CnH2n-ss... 

Not  many  membe 

rs  discovered. 

Hydrocarbons  of  the  series  CnHten+a  make  up  the  greater  portion  of 
the  paraffine  base  of  petroleums,  as  is  indicated  in  Table  9.  Members  of 
the  series  CnH  an  are  also  constituents  of  many  petroleums,  while  only  a 
few  of  the  higher  members  of  the  series  CnHan — 2  and  CnH2n — 4,  have 
been  found  in  oils  west  of  Pennsylvania.  The  aromatic  series,  CnH2n — e, 
occur  in  small  amounts  in  nearly  all  petroleums.  Occurrence  of  members  of 
the  other  series  is  somewhat  rare  in  petroleums,  and  are  in  small  amounts 
when  found  at  all. 

Fuel  Oil  and  Other  Products  of  Petroleum :  The  increasing  demand 
for  gasoline  and  other  petroleum  products  makes  it  very  undesirable  that 
crude  petroleum  as  obtained  from  the  wells  be  used  for  fuel.  Besides,  gaso- 
line in  a  fuel  oil  is  dangerous  on  account  of  the  increased  danger  of  explosions 
its  presence  entails.  Fuel  oil,  then,  is  a  very  indefinite  term  that  is  applied 
to  any  product  of  petroleum  used  for  the  production  of  heat  or  power. 
There  are  no  fixed  specifications  for  it,  and  consumers  order  it  to  suit  their 
requirements.  The  usual  grades  have  a  calorific  value  of  about  135000  B.  t. 
u.  per  gallon.  The  products  from  many  of  the  oil  refineries  west  of  the 
Mississippi  River  are  gasoline,  naphtha,  kerosene  and  fuel  oil,  while  Eastern 
refineries  usually  carry  the  fractionation  of  the  oil  much  farther,  their  output 
being  such  products  as  gasoline,  benzine,  naphtha,  kerosene,  light  machine 
oil,  automobile  oils,  cylinder  oils,  paraffin  wax  and  tar,  pitch,  or  coke. 


70 


FUELS 


SECTION   IV. 

GASEOUS  FUELS. 

Advantages  of  Gaseous  Fuels:  The  many  advantages  possessed  by 
gaseous  fuels  make  them  ideal  for  many  purposes.  Owing  to  their  gaseous 
state,  they  require  no  labor  in  handling,  and  their  freedom  from  foreign 
matter  eliminates  ash  and  danger  of  contamination.  As  the  temperature 
is  easily  controlled,  and  the  flame  can  be  directed  wherever  desired,  the 
working  conditions  of  a  furnace  may  be  kept  very  uniform.  The  kindling 
temperature  of  gases  is  between  650  C  and  700 °C,  and  the  speed  of  com- 
bustion is  practically  instantaneous  at  that  point,  which  fact  makes  it  easy 
to  attain  very  high  temperatures. 

Table  9.    The  Paraffin  Series  of  Hydrocarbons,  the  Members  of 

which  are  found  in  Natural  Gas  and  Petroleum  of  the 

Western  Pennsylvania  District. 

STATE  AT  EMPIRICAL        MELTING5 

ORDINARY  NAME  FORMULA 

TEMP. 


BOILING* 

POINT  POINT 

Deg.  C.  Deg.  C. 

,.  [Methane CH4                —184.0  —165.0 

|   Ethane C2H6              —171.4  —93.0 

. J    Propane C3H8              —195  —  45.0 

[Butane C4H10            —135  +       .1 

'Pentane C5H12            —130.8  36.3 

Hexane C6H14            —94.0  69.0 

Heptane C7H16            —97.1  98.4 

Octane C8H18            —56.5  125.5 

Nonane C9H20            —  51.0  150.0 

3   pecane C10H22           —31.0  173.0 

Undecane CnH24l          —  26.0  195.0 

Dodecane C12H26          —12.0  214.0 

Tridecane C13H28              -    6.0  234.0 

Tetradecane C14H80           + .  5.0  252.0 

Pentadecane . .    C15H32                10  270.0 

Hexadecane C16H34                18.0  287.0 

Octadecane C18Hs8                28.0  317.0 

Eicosane C20H42                37.0  

Tricosane C23H48  48.0 

Tetracosane C24H5o                51.0  

Pentacosane C25H52          53-54.0  

Hexacosane C26H54          55-56.0 

Octocosane C28H58                60.0  

Nonocosane C29H60           62-63.0  

Hentriacontane C8iH64  68.0 

Dotriacontane C82H66                70.0  

Tetratriacontane C84H7o          71-72.0 

Pentatriacontane C85H72 75.0 

See  American  Petroleum  Industry  by  Raymond  F.  Bacon  and  William  A.  Hamor, 
Published  by  McGraw-Hill  Book  Company,  New  York.  Also  Organic  Chemistry  by 
A.  F.  Holleman,  Fourth  English  Edition,  published  by  John  Wiley  &  Sons  Inc  ,  N  Y. 


GASES 


71 


Natural  Gas  is  the  most  remarkable  fuel  of  all.  Found  in  the  earth 
under  high  pressure  and  free  from  non-combustible  gases,  it  represents  a 
perfect  fuel.  Upon  being  regenerated  it  undergoes  partial  decomposition 
and  is,  therefore,  never  preheated,  but  with  it  the  highest  temperatures 
that  are  practical  are  easily  obtained  by  proper  manipulation.  The  sup- 
ply of  this  gas,  formerly  thought  to  be  inexhaustible,  is  now  declining  rapid- 
ly, and  this  fact,  combined  with  its  demand  for  domestic  purposes,  is  forcing 
its  use  in  the  metallurgical  and  other  industrial  arts  to  be  abandoned- 
Geologically,  natural  gas  is  closely  associated  with  petroleum  and  undoubt- 
edly is  of  similar  origin.  It  is  composed  of  the  lower  gaseous  hydro- 
carbons of  the  paraffin  series,  mainly  methane. 

Artificial  Gases  are  manufactured  from  coal.  The  method  of  manu- 
facture depends  on  the  end  sought.  Thus  in  retort  gases — coal  gas  and 
coke  oven  gas — only  the  volatile  products  of  the  coal  are  utilized  for 
gas,  while  in  the  gas  producer  the  whole  combustible  substance  of  the  coal 
is  converted  into  gas.  Of  these,  coal  gas  and  by-product  gas  most  nearly 
approach  natural  gas  in  calorific  power  and  efficiency.  Producer  gases 
always  contain  a  high  percentage  of  non-combustibles.  The  advantages 
in  favor  of  the  producer  are  that  an  otherwise  poor  fuel  may  be  converted 
into  a  desirable  one,  and  that  all  of  the  fuel  is  gasified.  As  to  blast  furnace 
gases,  their  utilization  under  boilers,  in  gas  engines,  and  in  blast  furnace 
stoves  represents  a  saving  that  amounts  to  millions  in  a  single  year.  A 
detailed  account  of  this  fuel  will  be  taken  up  later.  Table  10  below  shows 
useful  data  in  comparing  the  various  gaseous  fuels. 

Table  10.     Composition  of  Gaseous  Fuels. 

Representative  Analyses 
Percent  by  Volume 


Natural  Gas 

Coke 

Bench 

Carbu- 

Water 

Producer  Gas 

Blasb 

#1 

#2 

Oven 
Gas 

Coal 
Gas 

Water 
Gas 

Blue 
Gas 

#1 

#2 

nace 
Gas 

Carbon  Dioxide,  CO2 

.2 

.2 

1.7 

2.0 

3.0 

3.8 

5.0 

10.6 

12.9 

Illuminants  (asC2H4) 

.4 

.5 

3.0 

3.7 

10.0 

0 

.2 

.4 

o 

Oxygen,  O2  
CarbonMonoxide.CO 

0 
0 

.3 
.5 

.1 
3.5 

.8 
7.5 

.5 
34.0 

.5 
43.1 

0 

2'5.6 

0 
17.6 

0 

26.3T 

Hydrogen,  H2  
Methane,  CH4  

0 

77.7 

0 
94.5 

53.9 
34.6 

48.5 
33.0 

35.5 
12.0 

47.5 
.8 

10.2 
3.8 

11.8 
4.4 

3.7 

o 

Ethane,  C2H6  

19.4 

0 

not  det'd 

not  det'd 

not  det'd 

0 

0 

0 

o 

Nitrogen,  N2  

23 

4.0 

3.2 

4.5 

5.0 

4.3 

55.2 

55.2 

57.1 

*Net  B.t.u.  per  cu.ft. 

1027 

868 

518 

512 

465 

277 

148 

135 

94.8 

Gross     "       "      "  " 

1134 

963 

583 

573 

505 

301 

157 

146 

96  7 

Sulphur  per  lOOOcu.ft 

0 

0 

.8  Ibs. 

not  det'd 

not  det'd 

0 

.1  Ibs. 

.15  Ibs. 

0 

*Does  not  include  the  latent  heat  of  the  water  formed  in  combustion. 

Principle  of  the  Gas  Producer :  While  there  are  many  different  types 
of  gas  producer,  the  apparatus  is  essentially  a  vertical  cylindrical  shaft, 
lined  with  fire  brick,  partially  filled  with  coal  when  in  use,  through  which 
air,  or  steam  and  air,  are  forced  at  the  bottom  where  combustion  of  the 
non  volatile  part  of  the  coal  is  continuous.  In  its  upward  passage  the 
carbonic  acid  gas  formed  by  the  combustion  of  the  carbon  of  the  coal  is 
reduced,  in  part,  by  the  incandescent  fuel,  forming  carbon  monoxide. 
Part  of  the  water,  if  steam  is  used,  is  also  acted  upon  by  the  hot  coke, 
forming  carbon  monoxide  and  free  hydrogen,  and  some  methane  is 


72 


FUELS 


obtained  from  the  distillation  which  the  coal  undergoes  at  first. 

steam  is  used  with  the  air  the  producer  gives  a  gas  which  may 

composition  about  as  follows: 

Carbonic  Acid CO2—  5  to    9% 

Carbon  Monoxide CO  —18  to  27% 

Methane CH4—  2  to   4% 

Hydrogen H2— 10  to  18% 

Nitrogen N2— 48  to  55% 


In  case 
vary  in 


FIG.  10.    Sketch.    Section  Through  Gas  Producer. 


THE  GAS  PRODUCER  73 


Factors  Affecting  the  Efficiency  of  the  Producer:  The  greatest 
efficiency  of  the  gas  producer  is  attained  when  all  the  oxygen  of  the  injected 
air  is  caused  to  combine  with  carbon  to  form  only  carbon  monoxide,  provided 
the  excess  heat  thus  generated  is  also  made  available.  In  practice  these 
results  are  never  accomplished  entirely,  but  efforts  to  attain  them  have 
revealed  the  fact  that  they  can  be  most  nearly  approached  by  carefully 
regulating  the  temperature,  by  maintaining  perfect  uniformity  of  the 
working  conditions,  and  by  injecting  steam  with  the  air.  All  these  objects 
are  accomplished  in  fairly  efficient  degree  in  the  Hughes  mechanically 
poked  producer,  a  brief  description  of  which  follows: 

The  Hughes  Producer  as  an  Example  of  Mechanically  Poked  Pro- 
ducer: This  producer,  a  vertical  section  of  which  is  illustrated  in  the 
accompanying  sketch,  is  a  cylindrical  steel  shell,  j^g"  thick,  lined  with 
9  inches  of  first  quality  fire  brick,  and  closed  at  the  ends  with  water  sealed 
tops  and  bottoms.  When  ready  for  use  it  sets  with  its  base  resting  on  five 
wheels  which  are  mounted  on  a  frame  carried  on  a  concrete  foundation. 
By  means  of  gears  connected  to  a  driving  mechanism,  it  is  rotated  over 
these  wheels,  the  speed  of  rotation  when  in  use  being  1/10  r.  p.  m.  The 
top  plate  is  a  steel  casting  riveted  to  the  charging  floor,  under  which  the 
producer  itself  revolves.  It  contains  the  openings  for  the  gas  outlet,  the 
hoppers,  the  poker  and  the  observation  holes.  There  are  two  hoppers, 
through  which  coal  is  fed  to  the  producer,  one  on  each  side  of  the  outlet, 
but  they  are  at  different  distances  from  the  center  of  the  producer  to 
help  provide  even  distribution  of  the  coal.  A  bell  valve  closes  the 
base  of  the  hopper,  and  when  this  bell  is  dropped  to  dump  the 
coal  into  the  producer,  the  hopper  may  be  closed  by  sliding  a  circular 
plate  over  its  top.  There  are  several  holes  three  inches  in  diameter  at 
various  points  in  the  top  seal  for  observing  the  condition  of  the 
fire,  and  for  poking  out  clinkers;  these  holes  are  closed  with  water 
sealed  caps.  The  poker  is  a  round  hollow  steel  casting  with  a  forged 
steel  tip.  It  is  six  feet  in  length  and  tapers  from  eight  inches  in  diameter 
at  the  top  to  five  inches  at  the  tip.  The  poker  and  its  trunnions  are  water 
cooled,  the  water  being  admitted  through  the  trunnions,  then  passing 
through  the  poker  to  the  top  plate  which  is  covered  with  the  water  to  a 
depth  of  five  inches.  From  the  top  plate  the  water  flows  to  the  top  seal,  or 
trough,  around  the  top  plate,  then  through  a  drain  pipe  to  the  water  seal 
in  the  ash  pan.  The  top  of  the  poker  is  enclosed  in  a  gas  tight  mounting, 
and  is  so  mounted  that  the  poker  is  swung  back  and  forth  through  an  arc 
of  about  35°  by  means  of  eccentric  connections  from  the  producer  rotating 
mechanism.  A  full  stroke  of  the  poker  carries  its  tip  from  the  center  to 
the  side  wall  of  the  producer,  and  is  timed  to  occupy  3.21  minutes,  thus 
allowing  3.1  strokes  in  one  revolution  of  the  producer.  The  result  of  the 
rotating  motion  of  the  producer  and  the  backward  and  forward  action  of 
the  poker  is  to  produce  a  series  of  semi-ellipses,  so  that  the  poker  covers, 
in  a  period  of  70.72  minutes,  or  22  strokes,  practically  the  entire  area  of  the 


74  FUELS 


shell.  The  bottom  of  the  vessel  serves  as  an  ash  pan,  which  must  also 
be  water  sealed.  To  form  this  seal  the  bottom  is  made  in  the  form  of  a 
circular  trough,  which  is  attached  to  the  main  shell  of  the  vessel  so  that 
its  outer  rim,  or  lip,  extends  several  inches  beyond  this  circumference  of 
the  shell.  Into  this  trough  the  sealing  shell  of  the  producer  projects  to 
within  five  inches  of  the  bottom.  Since  this  construction  leaves  the  central 
portion  of  the  bottom  within  the  producer  somewhat  cone  shaped,  the 
ashes  are  deflected  toward  this  five-inch  opening  at  the  bottom  of  the  trough, 
where  they  may  be  removed  through  the  water  which  flows  from  the  top 
and  fills  the  trough  to  prevent  the  escape  of  gases.  The  steam  blower  is 
inserted  through  the  center  of  the  bottom  and  extends  some  twenty  inches  into 
the  producer,  where  it  is  capped  by  a  conical  hood  to  prevent  it  from  becom- 
ing choked  with  the  ashes.  The  mixture  of  steam  and  air  is  admitted  just 
beneath  this  hood  through  three  rows  of  small  openings  to  provide  for 
equal  distribution  of  the  blast.  The  ratio  of  steam  and  air  is  controlled 
by  the  openings  at  the  bottom  of  the  blower,  but  the  quantity  of  the  mixture 
admitted  to  the  producer  is  regulated  by  the  steam  pressure,  which  may 
be  changed  at  will  by  the  operator  from  the  charging  floor. 


Conditions  and  Reactions:  An  understanding  of  the  principle  and 
the  operation  of  the  producer  is  much  clarified  by  a  study  of  the  reactions 
and  conditions  prevailing  in  it  while  it  is  in  use.  A  study  of  the  conditions 
show  that  there  are  three  zones  or  belts  of  action  in  the  producer,  known 
as  the  distillation  or  top  zone,  the  reaction,  or  middle,  zone,  and  the 
combustion,  or  bottom,  zone.  Then,  below  these  zones  is  the  inactive,  or 
ash,  zone.  Thus,  upon  being  charged  into  the  producer,  the  raw  coal  is 
first  subjected  to  a  distillation  very  much  as  in  the  process  of  coking.  In 
this  top  zone  the  volatile  products  are  driven  off,  and  the  coal  is  converted 
into  a  kind  of  coke,  which  will  have  then  reached  the  reaction  zone.  Some 
of  this  coke,  passing  through  the  reaction  zone  unchanged,  reaches  the 
region  just  over  and  around  the  hood  of  the  blower.  Here  it  meets  the 
incoming  air,  and  having  been  heated  to  above  the  kindling  temperature, 
combustion  takes  place,  whereby  all  the  remaining  carbon  is  consumed 
according  to  this  simple  reaction,  C+O2=CO2+heat.  The  carbon  dioxide 
gas  thus  generated,  together  with  the  undecomposed  steam  and  other  gases. 
rises  at  once  into  the  reaction  zone.  Here  the  coke,  having  been  heated 
to  a  high  temperature  from  the  heat  liberated  by  the  above  reaction,  acts 
as  a  reducing  agent  toward  both  carbon  dioxide  and  water,  thus,  CO2+C+ 
heat=2  CO  and  H2O+C+heat=H2+CO.  It  will  be  noted  that  both 
these  reactions  absorb  heat,  but  that  only  the  second  is  under  control  and, 
hence,  available  for  lowering  the  temperature  in  the  producer.  The 
reduction  of  all  the  CO2  formed  in  the  combustion  zone  has  never  been 
brought  about,  so  that  a  small  quantity  is  always  present  in  producer  gas. 
The  relative  amounts  of  CO,  H2  and  CO2  in  the  final  gas  depends  to  a 
great  extent  upon  the  manipulation  of  the  producer.  As  to  the  other  com- 


SOLID  NATURAL  FUELS  75 

ponents  of  this  gas,  the  nitrogen,  being  introduced  with  the  oxygen  as  air, 
cannot  be  controlled,  while  the  hydrocarbons  such  as  CH4  and  C2H4  repre- 
sent products  of  the  distillation. 

Operation  of  the  Hughes  Producer :  The  ideal  conditions  in  a  Hughes 
producer  are  realized  when  the  combustion  zone  extends  to  about  a  foot 
above  the  top  of  the  blower  hood;  when  the  reaction  zone  is  from  one  and 
one-half  to  two  feet  thick;  when  the  distillation  zone  is  from  one-half  to 
one  foot  thick;  when  the .  conditions  are  such  that  the  ash,  the  coke 
and  the  coal  occur  in  level  zones;  and  when  the  amount  of  air  and  steam 
are  so  adjusted  that  the  fuel  is  properly -burned  without  excess  of  any  of 
the  undesirable  components  in  the  final  gas.  The  necessary  air  is  injected 
into  the  producer  by  a  steam  jet.  Thus  the  steam  serves  the  two-fold 
purpose  of  injecting  the  air  and  of  controlling  the  temperature  in  the  pro- 
ducer by  absorbing  heat,  during  its  decomposition,  which  later  appears  as 
potential  energy  in  the  gas.  This  lowering  of  the  temperature,  combined 
with  the  disintegrating  effect  of  the  steam  upon  the  ash,  tends  to  prevent 
clinkering.  If  too  much  steam  be  used,  the  temperature  in  the  reaction 
zone  will  drop  below  normal,  the  CO  will  be  low  and  the  percentage  of 
hydrogen  will  be  high.  This  condition  causes  the  gas  to  burn  with  a  short, 
intense  non-luminous  flame  that  has  a  detrimental  effect  upon  the  brick 
work  of  the  furnace  in  which  it  is  used,  especially  upon  the  ports  and  roof 
of  the  open  hearth  furnace.  But  the  judicious  use  of  steam  may  increase 
the  efficiency  of  the  producer  to  80  or  85%  of  the  heating  power  of  the  fuel. 
The  experienced  operator  judges  the  quality  of  the  gas  by  its  appearance, 
striving  for  a  dense  yellowish  blue  gas.  The  greatest  trouble  in  operating 
arises  from  the  accumulation  of  unburned  carbon  and  fine  ash  in  the  mains, 
which  must  be  cleaned  out  at  regular  intervals.  The  mains  are  brick 
lined  and  are  fitted  with  numerous  dust  catchers,  or  man  holes,  to  afford 
access  for  cleaning. 


SECTION   V. 

THE    SOLID   NATURAL  FUELS.  » 

Analysis  of  Solid  Natural  Fuels:  Upon  examination  all  the  solid 
natural  fuels  are  found  to  consist  of  combustible  and  non-combustible 
materials.  The  combustible  portion  is  composed  mainly  of  carbon  and 
hydrogen,  and  the  constituents  of  the  non-combustibles  are  water  and  a 
mixture  of  mineral  substances  called  ash.  By  the  gradual  application  of 
heat  without  access  of  air,  the  water  is  first  expelled,  which  is  followed 
closely  by  the  combustible  volatile  matter,  and  there  remains  a  non-volatile 
mass  composed  of  carbon,  called  fixed  carbon,  and  ash.  Upon  admitting 
air,  the  fixed  carbon  burns  readily,  leaving  only  the  ash.  A  similar  process 
carried  out  so  as  to  determine  the  amounts  of  these  four  classes  of  materials 
is  called  a  proximate  analysis.  There  are  two  general  methods  for  making 
a  proximate  analysis,  depending  upon  whether  or  not  it  is  desired  to  separate 


76 


FUELS 


the  volatile  matter  into  its  constituents.  These  are  often  referred  to  as 
the  American  and  the  European  methods,  the  latter  being  also  called  the 
progressive  distillation  method.  The  determination  of  the  percentages  of 
the  various  elements  present  in  the  fuel  constitutes  an  ultimate  analysis. 
The  following  analysis  of  a  coal  by  each  of  these  three  methods  will  illus- 
trate all  the  points  mentioned,  and  help  to  show  the  importance  of  the 
chemical  analysis. 


Table  11.     Analysis  of  a  Solid  Fuel,  Coal,  by  the  Three  Different 

Methods. 


fAsh  

.  .  .7.16%    Proximate 

/Ash....     7.160% 
*6\  Carbon    59.980 
Tar  •  5.420 

Fixed  Carbon  .  .  . 
Proximate   Volatile  Matter.. 
Analysis, 
American            Total  

.  59.98         Analysis, 
.  32.86      Progressive  • 

Distillation 
.100.00%    A/r  .->     , 

Free  NH3  285 
Comb.   NH8.       .041 
Moist  4.765 

/-\                                                                                    -|       f\  A  /» 

Method      Total  Sulphur.. 
Phosphorus  .... 

Method 
.     1.02% 
.     .005% 

Oxygen  1.046 
Volatile  Sulphur     .313 
Crude  Benzol...  1.353 

Total...  100.003% 


Ultimate  Analysis 


Ash  
C  

H  
N  

..     7.16% 
.  ..  79.41 
.  ..     5.14 
.  .  .     1.46 

O  

s... 

.  .  .     6.03 
1.02 

100.22% 


Wood:  This  very  interesting  substance  is  composed  mainly  of 
cellulose,  CoH10O5,  a  compound  formed  in  the  tree  or  plant  from  water 
taken  up  from  the  soil  and  carbon  dioxide  from  the  air.  The  change  is 
wrought  mainly  in  the  leaves  of  plants  through  the  agency  of  sunlight. 
Wood,  then,  represents  potential  energy,  the  original  source  of  which  is 
the  heat  from  the  sun,  and  it,  in  turn,  is  the  source  of  all  the  natural  solid 
fuels.  It  was  the  first  fuel  used  by  man,  and  for  centuries  was  the  principal 
one.  In  metallurgy  it  has  been  supplanted  by  coal,  though  for  some  purposes 
it  is  still  used,  mainly  in  the  form  of  charcoal  obtained  by  the  destructive 
distillation  of  wood.  The  calorific  power  of  dry  wood  is  about  half  that 
of  good  coal. 


PEAT,  WOOD,  COAL  77 


Peat  is  of  little  value  as  a  metallurgical  fuel.  It  finds  extensive  use 
in  Europe  as  a  domestic  fuel,  and  the  better  grades  may  be  successfully 
employed  in  gas  producers.  Its  chief  interest  lies  in  the  fact  that  it  is  the 
first  step  in  the  formation  of  coal.  Peat  results  from  the  decomposition 
of  wood  substance  out  of  contact  with  air.  It  is  formed  in  swamps  and 
marshes  from  water  plants  of  all  kinds  such  as  algae,  mosses,  sedges,  rushes, 
reeds,  shrubs,  like  willows,  and  even  trees.  A  species  of  moss  called 
sphagnum  is  especially  important  in  the  formation  of  peat.  It  grows  on 
the  surface  of  still  and  shallow  waters  with  only  a  small  portion  in  air, 
and  as  it  grows  the  submerged  portion  extends  farther  and  farther  beneath 
the  surface  until  the  bottom  is  reached.  Starting  growth  near  the  shore 
of  shallow  lakes,  it  gradually  extends  into  a  lake  until  the  whole  basin 
is  filled  with  soft  carbonaceous  matter,  and  a  bog  results.  This  growth  is 
followed  by  larger  growths,  until  the  former  lake  is  packed  with  carbonaceous 
matter.  The  accumulation  being  submerged,  the  carbon  compounds  of  the 
plants  are  slowly  decomposed,  by  which  process  the  carbon  is  isolated, 
though  a  part  escapes  with  hydrogen  and  oxygen  as  marsh  gas  and  carbon 
dioxide.  The  reaction  is  represented  thus: 

6C6H10O5        =    7CO2    +    3  CH4    + 14  H2O   +    C26H20O2 

Cellulose  or  Carbon         Marsh        Water        Peat  Substance 

Wood  Substance        Dioxide        Gas 

In  certain  geological  periods,  particularly  the  carboniferous,  the 
conditions  being  more  favorable  for  plant  growth  of  this  kind,  the  processes 
described  proceeded  more  rapidly  than  at  present,  with  the  result  that 
marshes  of  great  depth  and  area  were  filled  with  vegetable  growths.  These 
carbonaceous  deposits  were  subsequently  submerged  through  vertical 
movements  of  the  earth's  crust,  in  which  position  they  became  covered  by 
deposits  of  sedimentary  rocks.  Later  movements  of  the  earth's  crust 
raised  many  of  these  deposits  up  out  of  the  sea.  In  the  meantime  the  peat 
had  been  changed  into  coal. 

Lignite  and  Brown  Coal,  geologically  and  chemically,  occupy  positions 
intermediate  between  peat  and  coal.  They  were  formed  between  the 
Quaternary  and  Jurassic  periods  and  are  widely  distributed.  They  have 
low  calorific  power,  and  some  kinds  contain  as  much  as  15%  of  water. 
They  are  sharply  distinguishable  from  peat,  but  grade  into  coal  so  gradually 
that  no  one  has  attempted  to  distinguish  between  the  oldest  lignite  and 
the  youngest  coal.  The  relation  between  vegetable  and  mineral  fuels  are 
more  clearly  shown  by  the  accompanying  table  (12)  and  diagram  (Fig.  11). 


78 


FUELS 


Table  12.     Approximate  Analyses  of  the  Different  Solid  Fuels. 


Air  Dried 
Wood 

Air  Dried 
Peat 

Lignite 

Bituminous 
Coal 

Anthracite 
Coal 

c/ 

c/ 

o/ 

c/ 

c/ 

7o 

/o 

/o 

/o 

/o 

Vol.  M  

42-40 

30-60 

30-45 

20-45 

.5-6 

Fixed  C  

39-41 

11-40 

45-50 

40-85 

85-92 

Ash  

.15-2 

3-75 

4-15 

4-20 

2-15 

Moisture  or 

Water  

20-25 

6-20 

10-15 

1-6 

.5-4 

C.  P.  (Cals. 

per  Kilo). 

4600-5000 

2000-5000 

3000-6000 

7000-9000 

9000-9500 

90 
80 

70 
•60 


3* 


30 

201 
10 1 


-tVate 


Ash 


Wood 


Peat 


Lignite 


Bituminous 
Coal 


Anthracite 
Coal 


Graphit 


FIG.  11.     Graphic  Representation  of  Transformation  of  Fuels. 


PEAT,  WOOD,  COAL 


79 


Periods 

and 
Chief  Events 


Order 
of 

Strata 


Deposits 

of 
Valuable  Minerals 


Quaternary 

Glaciers  in  N.  E. 


Peat  in  East 
Lignite  in  West 
Petroleum  in  Tex.  and  Lou. 


Tertiary 
Rocky  Mountains 


Lignite  in  West 

Gold  and  Silver  in  West 

Oil  and  Gas  in  Wyo.  and  Cal. 


Cretaceous 

Rapid  Erosion,  W 


Lignite  in  West 
Chalk  in  So.  W. 


Petroleum  in  Cal. 
Colo,  and  La. 


Wyo.,  Tex., 


Mountains  West 

Jurassic 
Warping  of  Surface  E\^ , 


Potomac  Carbon  Rock 
Petroleum  in  Wyo. 

Limestone— Wyo.  and  Utah 


Triassic 


Coal  in  Va. 
Petroleum  in  Wyo. 


Slow  Folding  East 

Surface    Alternately 
Rises  and  Sinks 


Carboniferous 


Sea  Advances 


JVOCK  rtaii  01  i  exas 

Petroleum  both  East  and  Wcs1 

Coal 

Coal 

Coal 

Coal 

Coal 

Coal 

Coal 

Coal 

Gypsum 

Limestone  in  Middle  West 


Pennsylvania  District 


Sea  Retreats 


Devonian 

Sea  Advances 


Oil,  Gas— Pa.,W.Va.,0.,N.Y.Ind 
Limestone,  East 

Limestone,  East 
i  Sand  Stone 


Sea  Retreats 


Silurian 
Land  Submerged 


Clinton  Iron  Ores,  Ala. 
Oil-Gas  in  N.  Y.,  0..  Ind.,  111. 
and  Ky. 

Rock  Salt  in  N.  Y. 

Limestone 

Zinc  and  Lead 


Sand  Stone 
Limestone 


Cambrian 

Land  Submerged 


Huronian 


Laurentian 


Limestone 

Lake  Superior  Iron  Ores 
N/  |  Graphite 
Igneous  Rock 


Carboniferous  Period 
Coal  Beds 

of 
Western  Penna.  District 


Name 


Waynesburg 


Sewickley 
Redstone 
Pittsburgh 


Upper  Frteport 
Lower        " 


Upper Kittanning  4  ft. 


Middle 


_  Lower 


Clarion 
Brookville 


Thickness 


Max 


10ft 


6ft. 


6ft. 


9ft. 


8ft. 


5ft. 


3ft. 
8ft. 

2ft. 
5ft. 


Min. 


6  in. 


3ft. 


3ft. 


5ft. 


3  in. 


FIG.  12.    Diagram  Depicting  Geologic  Periods  in  which  Gas,  Oil  and  the 
Valuable  Minerals  are  Found  in  the  United  States. 


80  FUELS 


Coal :  This  mineral,  on  account  of  its  availability,  adaptability,  and 
high  calorific  power,  has  become  the  chief  source  of  energy  at  the  command 
of  man.  Used  both  in  its  natural  state  and  in  prepared  forms,  it  constitutes 
the  chief  metallurgical  fuel;  and  the  high  state  of  development  of  certain 
processes,  like  that  of  the  blast  furnace,  for  example,  have  been  possible 
only  through  the  peculiar  properties  of  this  remarkable  substance.  Its 
origin  and  history  is  as  remarkable  as  its  properties,  and  though  these 
subjects  belong  to  geology,  they  are  of  interest  to  the  metallurgist  because 
they  emphasize  the  need  of  conserving  the  fuel.  While  it  has  been  deposited 
in  immense  amounts,  the  supply  is  exhaustible  and  practically  fixed,  since 
the  rate  of  consumption  is  many  times  the  rate  at  which  it  is  being  formed. 
In  this  connection  a  study  of  Fig.  12  will  be  found  interesting. 

Bituminous  Coal:  All  coal  in  the  natural  state  may  be  looked  upon 
as  being  composed  of  coal  substance,  ash,  and  hydroscopic  water. 
Bituminous  coals,  on  account  of  their  peculiar  properties,  are  the  chief 
source  of  metallurgical  fuels.  The  coal  substance  of  these  coals  is  decom- 
posed by  distillation  into  carbon  and  a  mixture  of  volatile  compounds. 
During  this  process  some  kinds  fuse  into  a  pasty  mass,  leaving  at  the  end, 
when  all  volatile  matter  has  been  expelled,  a  strong  but  porous  mass  called 
coke.  It  is  not  known  what  the  coking  properties  of  coals  depend  upon. 
Coals  very  much  alike  in  physical  appearance  and  chemical  composition 
may  show  widely  differing  coking  qualities,  while  others  differing  in  both 
these  respects  produce  cokes  of  equal  quality.  During  the  coking  process, 
some  coals  expand  while  others  contract.  This  point  is  an  important  one 
in  by-product  practice,  because  expansion  wedges  the  coke  in  the  oven, 
making  it  difficult  to  remove,  and  causing  damage  to  the  oven  walls. 

Ash  in  Coal:  The  ash  in  coals  is  also  an  important  factor  in  their 
valuation.  Aside  from  decreasing  the  calorific  power,  it  affects  the  coal  in 
other  ways.  In  steam  coals  the  composition  of  the  ash  may  be  such  that 
it  fuses  at  a  low  temperature,  thereby  forming  large  clinkers;  or  it  may  be 
practically  infusible,  resulting  in  no  clinker,  with  the  result  that  a  suitable 
bed  of  coals  cannot  be  kept  on  the  grate,  due  to  the  fineness  of  the  ash. 
To  cite  a  concrete  example,  a  certain  coal  in  the  Pittsburgh  District  pro- 
duced ash  of  approximately  the  following  composition:  SiO2,  45%;  Al2Os, 
24%;  Fe2O8,  21%;  CaO,  7%;  MgO,  2%;  P2O5,  .6%.  Such  an  ash  is  moder- 
ately fusible,  and  so  is  most  desirable.  In  the  ash  is  found  the  phosphorus, 
which  determines  whether  coke  made  from  a  certain  coal  shall  be  used  for 
making  Bessemer  or  basic  iron.  The  sulphur  is  also  important.  In  the 
coal  it  is  present  mostly  as  FeS2,  which,  on  being  coked,  is  decomposed 
into  FeS  or  Fe-ySg  and  S,  and  on  burning,  it  is  completely  changed,  the 
iron  being  oxidized  to  Fe2O3,  or  Fe3O4  and  the  sulphur  to  SO2.  Often  a 
seam  of  good  quality  coal  is  divided  or  cut  horizontally  by  deposits  of  slaty 
material  known  as  bone  coal,  binder,  horse  back,  etc.,  all  of  which  must  be 
mined  with  the  coal.  Where  these  conditions  exist,  it  is  necessary  to  clean 


PULVERIZED  COAL  81 


the  coal  by  picking,  jigging,  or  washing.  As  a  rule  the  purest  coal  is  in 
the  middle  of  the  seam.  Phosphorus  in  particular  occurs  mainly  at  the 
top.  The  top  and  bottom  will  always  contain  the  highest  percentages  of 
ash  and  sulphur. 


SECTION    VI. 

PREPARED    SOLID   FUELS. 

Powdered  Coal :  It  has  long  been  known  that  the  combustion  of  finely 
pulverized  coal  presents  features  similar  to  those  encountered  in  burning 
gases.  When  mixed  with  air  and  ignited,  it  explodes;  and  when  it  is  blown 
into  a  heated  chamber  with  sufficient  quantity  of  air,,  complete  and  rapid 
combustion  approximating  that  of  the  fuel  gases  ensues.  These  facts  led 
to=  the  idea  of  using  pulverized  coal  as  a  substitute  for  gaseous  fuels.  Though 
first  attempted  about  100  years  ago,  no  progress  was  made  in  its  use  until 
recently,  owing  to  the  difficulties  of  securing  the  proper  conditions,  and  also 
to  the  abundance  of  other  desirable  fuels.  Although  still  in  the  experimental 
stage,  it  is  now  used  very  successfully  and  gives  promise  of  replacing  gaseous 
fuels  for  metallurgical  and  many  other  uses. 

Requirements:  The  use  of  powdered  coal  necessitates  meeting  the 
following  requirements: 

1.  With  the  apparatus  now  in  use,  only  high  volatile  coals  (volatile 

matter  over  30%)  may  be  used. 

2.  The  coal  must  be  very  finely  pulverized.     Approximately,  70% 

should  pass  a  300  mesh  sieve,  80%  a  200  mesh,  and  95%  a  100 
mesh. 

3.  The  dust  must  be  injected  into  the  furnace  in  such  a  manner  that 

each  particle  enters  the  combustion  chamber  surrounded  with 
air. 

4.  If  the  coal  is  to  be  used  in  regenerative  furnaces,  special  checker 

work  that  will  permit  of  easy  cleaning  is  required.  A  high 
percentage  of  ash  is  drawn  out  with  the  gases,  which  quickly 
clogs  ordinary  checkers. 

5.  Careful  regulation  of  draft  to  give  a  low  velocity  of  the  air  and  gases 

is  necessary  to  secure  complete  combustion,  since  the  dust  burns 
more  slowly  than  gases.  This  precaution  also  prevents  rapid 
clogging  of  checkers  when  the  fuel  is  used  in  regenerative  furnaces. 

The  pulverizing  of  coal  makes  it  necessary  to  dry  it  thoroughly,  and 
necessitates  the  installation  of  special  appliances  for  handling  the  dust, 
which  can  be  done  only  through  pipes  and  tightly  closed  bins.  Two  general 


82  FUELS 


methods  of  handling  are  available,  namely,  the  worm  screw  and  the 
pneumatic.  The  third  requirement  calls  for  special  burners,  so  constructed 
as  to  permit  of  the  regulation  of  the  amounts  of  both  air  and  dust  and  the 
adjustment  of  the  direction  of  the  flame.  The  equipment  will  consist,  then, 
of  a  dryer,  a  pulverizer,  separator,  conveyors,  bins,  burners,  and  air  com- 
pressors, with  the  necessary  motors  or  engines.  Added  to  these,  in  many 
cases,  will  be  the  special  regenerators  previously  mentioned. 

t 

Advantages  of  Powdered  Coal:  It  is  adaptable  for  use  wherever  large 
amounts  of  fuel  are  consumed,  and  many  claims  as  to  its  advantages  are 
made.  As  compared  with  producer  gas  to  fire  open  hearth  furnaces,  for 
example,  it  is  said  to  be  as  efficient  and  convenient  as  the  gas  and  to  give 
a  more  regular  supply  of  heat.  It  is  cheaper  to  prepare  than  producer  gas, 
increases  the  production  of  steel  10%  or  more,  and  reduces  the  loss  by 
oxidation — all  without  contamination  of  the  steel  from  impurities  in  the 
ash,  if  proper  conditions  prevail. 

The  Sharon  Plant :  The  appliances  for  preparing  and  burning  the  coal 
vary  in  form  and  method.  A  brief  description  of  the  installation  at  the 
Sharon  Works  of  the  Carnegie  Steel  Company,  which  is  equipped  to  supply 
three  40-ton  basic  open  hearth  furnaces,  may  serve  as  an  example  of  one  of  the 
methods  employed  in  its  use.  This  plant  was  the  first  of  the  Carnegie 
Company's  to  use  this  fuel  in  the  open  hearth.  The  installation  is  that 
of  the  Raymond  Bros,  of  Chicago,  who  employ  an  impact  pulverizer  with 
an  air-separating  system. 

Description  of  Pulverizing  Plant:  The  building  in  which  the  pulver- 
izing is  done  is  separated  from  the  open  hearth  building  by  about  75  yards. 
Outside  this  building,  is  a  small  trestle  storage  bin  to  which  the  coal, 
crushed  to  pass  a  one  inch  ring,  is  delivered  from  the  cars.  From  this  bin 
the  coal  is  Delivered  by  a  motor  driven  belt  conveyor  to  the  elevated  end 
of  a  revolving  cylindrical  dryer,  about  30  ft.  long  and  5  ft.  in  diameter, 
inclined  at  an  angle  of  about  10°.  By  revolving  this  dryer,  the  coal  is 
caused  to  pass  slowly  toward  the  lower  end,  and  in  so  doing  it  is  stirred 
and  scattered  in  the  cylinder,  so  as  to  be  thoroughly  dried  by  a  forced 
circulation  of  an  atmosphere  of  hot  gases  from  a  small  brick  furnace  located 
at  the  elevated  end  of  the  furnace.  These  gases  are  conducted  from  the 
furnace  to  the  lower  end  of  the  dryer  by  a  stationary  flue,  about  18  inches 
in  diameter  and  concentric  with  the  external  cylinder.  Upon  reaching  the 
lower  end  of  the  dryer,  the  coal  is  discharged  into  a  hopper  bin  from  which 
it  is  elevated  vertically  a  distance  of  about  20  ft.,  by  means  of  belt  buckets, 
to  a  25-ton  storage  bin.  From  this  bin  it  is  fed  by  gravity  to  the  pulverizer, 
through  the  opening  of  which  it  is  mechanically  fed  at  a  rate  adjusted  to 
the  speed  of  the  pulverizer,  which  has  a  capacity  of  5  tons  per  hour. 
Through  a  pipe,  about  16  inches  in  diameter,  leading  from  the  top  of  the 
pulverizer,  the  finest  dust  is  pneumatically  elevated  to  a  cone  shaped  cyclone 


POWDERED  COAL  83 


separator,  about  6  ft.  in  diameter  and  some  70  ft.  above  the  pulverizer. 
The  mixture  of  air  and  dust  enters  at  the  top  of  the  separator  on  a  tangent, 
and  is,  therefore,  given  "a  swirling  motion  at  the  same  time  that  its  velocity 
is  reduced.  The  air,  carrying  very  little  dust,  is  forced  out  through  a  pipe, 
about  24  inches  in  diameter,  inserted  in  the  center  of  the  top  of  the  separator. 
Through  this  pipe  the  air  is  returned  to  the  pulverizer,  completing  the 
circuit.  By  this  arrangement  the  dust  in  the  air,  on  entering  the  separator, 
is  subject  to  the  double  effect  produced  by  the  whirling  motion  and  the 
reduction  in  speed — namely,  centrifugal  force  and  gravity — with  the  result 
that  it  is  precipitated  upon  the  inclined  wall  of  the  separator  and  falls  out 
at  the  bottom  through  a  rectangular  chute  (about  6"x8")  leading  vertically 
down  to  a  12-inch  screw  conveyor,  which  carries  the  dust  to  the  distributing 
conveyor  located  above  the  open  hearth  furnaces.  This  conveyor,  extending 
at  right  angles  to  the  12-inch  one,  distributes  the  dust  to  six  9-ton  bins,  one  of 
which  is  located  above  and  at  each  end  of  each  furnace.  The  bottoms  of 
these  bins  are  connected  to  small  4-inch  screw  conveyors,  driven  by  variable 
speed  motors,  which  feed  the  dust  to  the  burners  at  any  speed  desired. 
Falling  vertically  through  a  4-inch  pipe,  the  dust  passes  through  a  1-inch 
opening  into  a  2-inch  horizontal  pipe  where  it  is  met  at  right  angles  by  a 
jet  of  compressed  air.  This  jet  blows  the  dust  through  the  2-inch  pipe  a 
distance  of  about  8  inches  into  a  5-inch  nozzle,  some  16  inches  long,  where 
it  is  mixed  with  a  larger  volume  of  air  under  the  low  pressure  of  16  inches 
of  water.  The  velocity  of  this  air  is  sufficient  to  carry  the  dust  into  the 
furnace  through  a  water  cooled  opening,  where  it  comes  in  contact  with 
regenerated  air  and  is  completely  burned.  The  air  blown  in  through  the 
burner  is  about  25%  of  the  total  required  for  combustion. 

Clairton  and  Homestead  Plants:  More  recent  and  much  larger 
installations  for  powdered  coal  have  been  made  at  Clairton  and  Homestead. 
The  plant  at  Clairton  id  equipped  to  supply  5  of  the  16  sixty-ton  open  hearth 
furnaces,  while  the  one  at  Homestead  is  designed  to  furnish  fuel  for  the 
whole  of  the  No.  3  open  hearth  plant,  which  consists  of  twenty-four  60-ton 
furnaces.  At  both  these  plants  the  drying,  pulverizing  and  conveying 
equipment  is  practically  the  same  in  kind  as  that  used  at  Sharon,  but  a 
different  type  of  burner  is  used.  While  the  burners  at  Sharon  are 
mechanically  fed,  at  Clairton  and  Homestead  they  are  wholly  pneumatic. 
The  principle  of  the  pneumatically  fed  burners  is  easily  understood  from  a 
description  of  the  apparatus.  The  arrangement  of  the  burner  is  shown  in  the 
accompanying  drawing,  Fig.  14.  It  consists  of  a  delivery  pipe,  1^4,  inches  in 
diameter  by  2  feet  3  inches  long,  a  compressed  air  nozzle,  and  a '  'cross, ' '  which 
is  a  small  casting  containing  a  3-inch  cubical  cavity.  The  nozzle,  Y%  inches  in 
diameter  inside,  passes  through  one  side  of  the  cross,  then  across  the  cavity 
and  enters  the  delivery  pipe  inserted  in  the  opposite  side,  so  as  to  give  an 
injector  effect  that  draws  the  dust  through  the  one  inch  opening  shown  by  the 
dotted  lines  of  the  drawing.  This  opening  is  connected  by  a  suitable  pipe 
to  a  cast  iron  feeder  box  attached  to  the  bottom  of  the  storage  bin,  located 


84 


FUELS 


some  ten  feet  away.  This  box,  about  twelve  by  fourteen  inches  in  cross 
section,  is  in  the  form  of  an  elbow.  One  end  is  bolted  to  the  bottom  opening 
of  the  bin,  while  the  other  is  closed  with  a  steel  plate.  The  pipe  leading 
to  the  burner  is  inserted  in  an  opening  on  the  top  of  the  horizontal  portion 


of  the  box.  With  all  connections  between  burner  and  feeder  box  tight,  the 
operation  of  the  burner  is  very  simple.  By  means  of  a  valre,  not  shown 
in  the  drawing,  compressed  air  delivered  under  a  pressure  of  about  eighty 
pounds  may  be  admitted  through  the  nozzle,  when  the  suction  draws  the 


COKE  85 


coal  dust  from  the  feeder  box  and  blows  it  through  the  delivery  pipe  into 
the  furnace.  It  will  be  observed  that  the  design  of  this  burner  is  based 
upon  the  principle  that  the  quantity  of  fuel  dust  injected  into  the  furnace 
is  controlled  by  the  quantity  of  air  passing  through  the  injector.  The 
threaded  hole  in  the  top  of  the  cross  provides  a  means  of  attaching  the 
burner  to  its  supports. 

Coke.  Coke  is  the  residue  that  remains  after  certain  bituminous  coals 
have  been  subjected  to  destructive  distillation.  Owing  to  its  peculiar  struc- 
ture and  physical,  or  mechanical,  properties,  it  has  become  the  chief  metal- 
lurgical fuel.  All  coke  possesses  a  cellular  structure,  but  there  is  a  wide 
variation  in  the  degree  of  porosity  for  different  cokes.  Likewise  the  hardness, 
brittleness  and  strength  of  coke  is  subject  to  wide  variations.  Coke  for 
blast  furnace  consumption  should  be  of  a  porous  character  to  admit  of  ready 
combustion,  and  it  must  at  all  times  be  sufficiently  strong  to  resist  pressure 
due  to  the  heavy  burden  without  crushing.  In  chemical  composition,  the 
different  cokes  show  a  similar  wide  variation,  though  for  metallurgical 
purposes  the  fixed  carbon,  which  is  the  only  constituent  sought,  will  con- 
stitute 85  to  90%  of  the  coke.  The  other  constituents,  roughly  stated  as 
ash,  sulphur  and  phosphorus,  are  impurities.  The  per  cent,  of  phosphorus 
in  the  coke  determines  whether  the  coke  is  suitable  for  making  Bessemer 
or  basic  iron.  For  the  former  grade,  modern  practice  requires  that  the 
phosphorus  content  of  the  coke  must  not  exceed  .018%.  The  sulphur  content 
ranges  from  .60%  to  1.50%,  though  it  is  evident  that  both  the  sulphur  and 
ash  should  be  kept  as  low  as  possible. 

Methods  of  Manufacturing  Coke:  There  are  two  methods  for  the 
manufacture  of  coke,  known  as  the  beehive  and  the  by-product,  or  retort, 
process.  In  the  beehive  process,  air  is  admitted  to  the  coking  chamber 
for  the  purpose  of  burning  therein  all  of  the  volatile  products  of  the  coal 
to  generate  heat  for  further  distillation.  Incidentally,  some  of  the  fixed 
carbon  of  the  coal  is  also  consumed.  In  the  other  method,  the  coking 
chambers  are  air  tight,  and  the  necessary  heat  for  distillation  is  supplied 
from  external  combustion  of  the  volatile  products  of  the  coal;  and  with 
modern  ovens,  properly  operated,  only  about  half  of  the  gaseous  matter 
from  the  coal  is  used  in  carrying  on  the  coking  process.  While  the  beehive 
process  was,  until  recently,  the  leading  method  for  the  manufacture  of  coke, 
it  is  fast  being  replaced  by  the  by-product  process.  The  processes  of  manu- 
facture have  very  little  effect  on  the  quality  of  the  coke,  but  if  there  is  any 
difference,  the  latter  process  has  the  advantage.  There  is,  however,  a 
difference  in  appearance,  due  mainly  to  the  difference  in  the  coking  temper- 
ature of  the  two  processes,  that  of  the  by-product  being  much  lower  than 
the  beehive.  In  general,  beehive  coke  is  silvery  gray  in  appearance,  while 
by-product  coke  is  of  a  much  darker  color.  As  examples  of  these  two 
methods  of  coking,  the  following  brief  descriptions  of  plants  are  to  be  taken 
as  typical  of  the  best  modern  practice  for  each  process. 


86  FUELS 


SECTION    VII. 

THE   BEEHIVE    PROCESS   FOR  THE    MANUFACTURE   OF   COKE. 

The  Continental  No.  1  Plant  of  the  H.  C.  Frick  Coke  Company 

may  be  cited  as  an  example  of  beehive  coke  practice.  It  is  located  near 
Uniontown,  Pa.,  in  the  southeastern  part  of  the  famous  Connellsville  coke 
region.  It  consists  of  a  coal  mine  and  a  coking  plant  of  400  beehive  ovens. 

The  Mine:  Since  the  coal  bed  here  lies  about  330  feet  below  the 
surface,  the  coal  is  mined  through  a  shaft.  Although  some  gas  is  given 
off  as  the  coal  is  mined,  it  is  prevented  from  collecting  and  thus  becoming 
dangerous  by  a  very  efficient  system  of  ventilation,  which  permits  the 
installation  of  electrical  appliances  for  lighting  and  the  use  of  both  pick 
and  machine  methods  of  mining.  The  coal  seam  in  this  mine  varies  from 
seven  to  nine  feet  in  thickness,  but  in  mining  the  coal,  about  four  inches 
at  the  bottom  and  from  four  to  eight  inches  at  the  top,  being  high  in  ash, 
sulphur  and  phosphorus,  is  allowed  to  remain  in  order  to  improve  the  quality 
of  the  coke.  Incidentally,  this  top  discard  also  helps  to  support  the  gob, 
an  easily  dislodged  and  treacherous  slate-like  formation  lying  between  the 
coal  and  the  hard  overlying  rock  deposit  and  forming  the  roof  of  the  mine. 
The  average  output  of  the  mine  is  twelve  hundred  net  tons  per  day.  POT 
transporting  this  coal  through  the  mine  underground,  a  combination  system 
of  electric  and  rope  haulage  is  employed  from  certain  points,  while  horses 
are  used  to  distribute  empty  cars  to  and  assemble  loaded  cars  from  the 
various  working  places.  From  these  assembling  points  the  loaded  cars 
are  moved  by  electric  locomotives  in  trains  of  thirty  cars  each  to  a  sub- 
station, where  they  are  attached  to  the  rope  haulage  which  pulls  them  to 
the  foot  of  the  shaft.  Here  they  are  hoisted,  one  at  a  time,  to  the  tipple 
and  automatically  dumped  into  bins.  From  these  bins  the  coal  is  loaded 
by  chutes  into  electric  larries  which  convey  it  to  the  ovens  some  hundred 
yards  away.  Each  larry  holds  sufficient  coal  to  charge  one  oven,  and  it 
will  be  noted  that  run-of-mine  coal  is  used  for  coking,  no  crushing  nor 
preparation  of  any  kind  being  necessary. 

Construction  and  Arrangement  of  the  Ovens:  As  to  the  essential 
features  of  construction,  the  name  beehive  is  literally  descriptive  of  the 
form  of  the  beehive  oven.  The  dome-like  chamber,  built  on  a  suitable 
foundation,  is  constructed  of  highly  refractory  brick,  has  a  flat  but 
slightly  sloping  bottom,  an  opening  in  the  top,  the  "trunnel  head,"  through 
which  the  coal  is  charged  and  the  products  of  distillation  and  combustion 
escape,  and  an  arched  opening  at  the  bottom,  called  the  door,  through 
which  air  is  admitted  for  combustion  and  the  coke  is  watered  and  drawn. 
In  general,  the  dimensions  of  different  ovens  vary  a  great  deal.  The  ovens 
at  this  plant  are  each  12  feet  3  inches  in  diameter  and  8  feet  high  from  the 
bottom  to  the  top  of  the  dome,  inside  dimensions.  Of  this  height,  the  side 
wall,  built  of  fire  brick,  rises  vertically  a  distance  of  27  inches,  and  is  capped 


BEEHIVE  COKE  87 


by  the  crown  which  is  built  of  silica  brick.  Except  in  the  case  of  the  special 
brick  used  about  the  openings,  the  brick  in  these  walls  are  of  standard 
size  and  are  laid  ends  in  and  out,  thus  making  both  the  side  wall  and  the 
crown  wall  approximately  9  inches  thick.  Finally,  this  brick  structure  is 
covered  on  the  outside  and  up  to  the  level  of  the  "trunnel  head,"  which  is 
14  inches  in  diameter,  with  loam  or  rough  clay  which  acts  as  an  insulator  of 
and  a  store  house  for  heat.  For  retaining  this  loam  covering,  there  are  in 
general  three  different  arrangements  of  ovens  as  follows:  (1)  the  bank 
system,  in  which  the  ovens  are  built  in  single  rows  against  a  bank  of  earth, 
natural  or  artificial,  thus  making  it  necessary  to  build  but  one  retaining  wall 
along  the  front  of  the  ovens;  (2)  the  single  block  system,  which  consists 
of  a  single  row  of  ovens  with  retaining  walls  at  both  the  front  and  back; 
and  (3)  the  double  block  system,  in  which  the  ovens,  in  a  double  row,  are 
built  back  to  back  or  staggered  with  a  retaining  wall  extending  along  the 
front  of  each  row.  At  this  plant  there  are  four  double  block  batteries  and 
two  batteries  of  banked  ovens. 

Waste  Heat  System :  One  battery  of  the  banked  ovens,  forty  in  number, 
is  arranged  for  utilizing  the  waste  heat  from  the  products  of  combustion 
to  generate  steam.  For  this  purpose  a  large  tunnel  is  constructed  in  the 
bank  some  10  feet  back  of  the  ovens  and  parallel  to  the  battery.  This 
tunnel  is  connected  to  each  oven  by  means  of  a  small  flue,  which  conducts 
the  hot  gases  out  of  the  oven  from  an  opening  sufficiently  above  the  side  wall 
to  prevent  its  being  closed  by  the  largest  charge  of  coal  used.  Each  flue 
is  provided  with  a  damper  for  closing  off  the  draft  during  the  period  the 
oven  is  being  watered,  drawn  and  charged.  From  the  battery,  the  tunnel 
passes  to  the  boiler  house,  where  branches  conduct  the  hot  gases  through 
the  fire  boxes  and  flues  of  the  boilers  which  are  connected  to  a  common 
stack,  about  100  feet  in  height  to  cause  the  proper  draft.  During  the  coking 
period,  the  "trunnel  head"  is  necessarily  kept  tightly  closed.  Owing  to  the 
increased  draft,  these  ovens  are  inclined  to  run  up  a  little  higher  temper- 
ature than  the  ordinary  oven,  so  that  the  temperature  in  the  tunnel  is 
high,  sometimes  reaching  1500°C.  A  maximum  of  about  800  horsepower 
is  generated  from  the  waste  heat  from  this  battery  of  forty  ovens. 

Charging  the  Ovens:  The  ovens  are  charged  as  soon  as  practicable 
after  drawing,  so  that  the  stored  up  heat  from  the  previous  charge  will  be 
sufficient  to  start  the  coking  process.  In  the  case  of  new  work,  the  ovens 
must  be  heated  up  gradually  to  a  coking  temperature  by  means  of  wood 
and  coal  fires,  after  which  period  small  charges  of  coal  for  coking  are  used 
until  the  ovens  reach  normal  working  conditions.  With  the  oven  in 
readiness  for  charging,  the  door  is  bricked  up  to  within  about  one  and  one 
half  inches  of  the  top;  and  the  charge,  which  consists  of  six  and  one  half 
tons  of  coal  for  48-hour  coke  and  eight  tons  for  72-hour  coke,  the  latter 
being  made  over  the  week-ends,  is  dropped  through  the  "trunnel  head"  from 
the  larry  above,  leaving  the  coal  in  a  cone  shaped  pile  in  the  oven.  In 


88  FUELS 


order  to  secure  uniformity  in  the  coking  of  the  coal,  this  pile  must  be 
levelled  so  that  the  coal  wi'l  lie  in  a  bed  of  uniform  depth  over  the  entire 
bottom  of  the  oven.  This  result  is  attained  by  means  of  an  electrically 
operated  leveling  machine,  which  is  moved  from  oven  to  oven  on  the 
same  tracks  that  the  charging  larry  uses.  The  essential  part  of  this 
machine  consists  of  a  vertical  rod  and  sleeve,  on  the  lower  end,  or  head, 
of  which  is  mounted  two  collapsible  leveling  arms.  By  means  of  suitable 
gear  connections  with  an  electric  motor,  this  apparatus,  with  the  head 
closed,  may  be  mechanically  lowered  through  the  "trunnel  head"  upon  the 
apex  of  the  pile  of  coal,  when  the  rod  and  sleeve  are  made  to  revolve  and 
the  leveling  arms  are  at  the  same  time  slowly  extended.  These  motions, 
combined  with  the  continued  lowering  of  the  head,  distribute  the  coal  to  a 
uniform  depth  in  a  very  few  minutes.  In  works  not  equipped  with  this 
machine,  the  leveling  is  accomplished  by  means  of  a  large  long-handled 
scraper,  operated,  by  a  laborer,  through  the  door  of  the  oven,  which  is 
purposely  bricked  up  to  about  only  two-thirds  of  its  height  at  the  time  of 
charging. 

The  Coking  Process  begins  very  soon  after  the  levelling  is  completed, 
as  the  ovens  retain  enough  heat  in  the  brick  of  the  walls  and  the  loam  backing 
to  start  the  distillation  of  the  volatile  matter  of  the  coal.  As  more  and  more 
heat  is  conducted  through  the  walls  from  the  hot  loam  backing,  the  tem- 
perature of  the  interior  of  the  oven  soon  reaches  the  kindling  point  for  these 
volatile  gases,  which,  in  the  presence  of  the  air  admitted  to  the  oven,  ignite 
with  a  slight  explosion  at  first,  then  continue  to  burn  quietly  in  the  crown 
of  the  oven,  or,  as  small  candle-like  flames  at  the  surface  of  the  coking 
mass,  thus  supplying  heat  to  continue  the  process.  The  coking  proceeds 
from  the  top  of  the  coal  downward,  so  that  the  coking  time  depends  mainly 
upon  the  depth  of  the  coal.  The  volume  of  volatile  matter  thus  rapidly 
approaches  a  maximum,  which  is  maintained  for  a  period,  then  declines  to 
practically  nothing,  hence  the  burning  of  this  volatile  matter  must  be 
regulated  by  gradually  closing  up  the  opening  at  the  top  of  the  door  for  the 
admission  of  air.  This  regulation  is  very  necessary  to  maintain  the 
temperature  at  a  maximum,  and  conserve  coke,  as  an  excess  of  air  at  the 
beginning  of  the  coking  period  tends  to  cool  the  oven,  and  later  con- 
sumes the  carbon  of  the  coke.  The  yield  is  also  reduced  by  improper 
leveling.  If  the  coal  is  not  of  uniform  depth  to  begin  with,  the  thin  portions 
coke  through  before  the  thick,  and  some  of  the  coke  in  the  thin  sections 
is  consumed  while  the  coking  of  the  thick  portions  is  being  completed. 
On  the  other  hand,  if  the  process  be  stopped  when  the  thin  areas  have 
coked  through,  there  will  be  a  loss  due  to  green  butts  on  the  thick  areas. 
It  will  be  recalled  that  the  coal  assumes  a  semif  used,  or  pasty,  state  during 
the  coking  process.  The  result  to  be  expected  from  such  behavior  is  that 
the  coke  would  be  found  in  a  continuous  mass,  or  cake,  at  the  end  of  the 
process;  but,  due  to  expansions  and  contractions  of  the  mass  in  coking  and 
on  cooling,  the  cake  is  ramified  by  a  great  number  of  irregular  vertical 


BEEHIVE  COKE 


89 


fissures,  thus  giving  it  a  long  columnar  structure,  in  which  the  very  irregular 
columns  extend  from  the  top  to  the  bottom  of  the  cake.  This  structure 
affords  a  second  means  by  which  beehive  coke  can  be  distinguished  from 
by-product. 


Fia.  15.     Ideal  Section  of  Beehive  Coke  Oven  Showing  Watering  Machine 
in  Use  and  Structure  of  Coke. 


Watering  and  Drawing  the  Coke:  As  soon  as  the  volatile  matter 
has  ceased  to  be  evolved,  as  indicated  by  a  subsidence  of  the  smoke  at 
the  "trunnel  head"  and  a  decided  shortening  of  the  candle  flames  on  the 
surface  of  the  coke,  the  coke  should  be  drawn.  In  good  practice,  the  charge 
will  be  so  regulated  that  this  point  is  reached  near  the  coking  time  assigned, 
and  the  ovens  will  be  drawn  on  a  schedule.  If  any  circumstances  delay 
the  drawing,  the  doors  of  the  ovens  are  sealed  tight  with  clay,  and  the  draft 
at  the  "trunnel  head"  is  reduced.  However,  it  is  very  important  that  the 
ovens  be  drawn  on  schedule,  as  a  delay  results  in  burning  some  coke  and 
in  cooling  the  oven,  so  that  it  will  not  coke  the  next  charge  in  the  period 
assigned.  At  the  end  of  the  coking  time,  then,  the  brick  work  closing  the 
door  is  torn  out,  and  the  coke  is  watered  out.  At  Continental  this  watering 
is  accomplished  by  a  self  propelled  spraying  device.  It  consists  of  a  tube 
or  pipe  a  few  inches  shorter  than  the  diameter  of  the  oven,  pivoted  at  the 
center  to  a  feed  pipe  and  perforated  by  two  rows  of  holes  on  opposite  sides, 
starting  from  the  center.  The  holes  are  arranged  to  throw  jets  of  water 
horizontally,  which  causes  the  pipe  to  revolve.  Where  this  device  is  not 


90  FUELS 


provided,  the  ovens  are  watered  by  spraying  with  a  pipe  on  the  end  of  a 
hose  in  the  hands  of  a  laborer,  who  directs  a  stream  of  water  through  the 
door  of  the  oven.  For  drawing  the  coke,  a  Covington  coke  drawing  machine 
is  employed  at  this  plant.  It  is  provided  with  a  long  arm  fitted  with  a 
head,  flat  on  the  bottom,  but  inclined  on  the  top,  and  a  pair  of  hinged  ears, 
or  drawing  lugs.  Upon  being  pushed  by  motor  into  the  oven,  the  head 
moves  in  advance  of  the  drawing  lugs,  which  lie  flat,  and  raises  the  coke 
from  the  bottom  of  the  oven.  Upon  the  return,  the  lugs  engage  this  loosened 
coke  and  force  it  through  the  door  in  advance  of  the  head.  Here  the  coke 
falls  upon  a  belt  conveyor  running  parallel  to  the  ovens,  and  is  carried  to 
the  loading  conveyor,  which  is  inclined  and  extends  at  right  angles  to  the 
row  of  ovens.  At  the  top  of  the  loading  conveyor  the  coke  falls  upon  a 
stationary  screen,  to  separate  the  breeze,  then  slides  down  a  chute  into 
a  railroad  car,  and  is  ready  for  shipment.  It  is  impossible  to  remove  all 
the  coke  with  the  machine,  and  what  remains  must  be  drawn  by  hand,  so 
while  the  machine  moves  forward  to  the  next  oven,  a  laborer  cleans  out 
the  oven  with  a  long  handled  scraper,  drawing  the  coke  out  upon  the  con- 
veyor of  the  machine,  which  is  more  than  long  enough  to  span  the  distance 
between  the  doors  of  two  adjacent  ovens.  In  straight  hand  drawing,  the 
coke  is  drawn  out  into  the  yard  and  forked  into  barrows,  which  are  used 
to  wheel  the  coke  into  railroad  cars. 

Longitudinal  Ovens:  In  order  to  adapt  better  the  beehive  oven  to 
the  use  of  mechanical  devices  and  effect  a  saving  in  labor,  there  appeared 
in  1906  a  modified  form  of  the  old  Belgian  oven,  known  as  the  Mitchell 
oven.  The  essential  features  of  this  type  of  oven  are  a  long  narrow  chamber, 
rectangular  in  shape,  with  a  flat  tile  bottom,  an  arched  roof  sloping  towards 
the  ends,  a  "trunnel  head"  in  the  center  of  the  roof,  and  two  doors,  one  at 
each  end,  which  extend  over  the  entire  width  and  height  of  the  oven  ends. 
These  ovens  are  built  side  by  side  in  blocks  or  batteries,  and  are  charged, 
controlled  and  watered  like  beehive  ovens.  The  coke  is  pushed  out  of  the 
oven  by  a  mechanical  pusher  upon  a  loading  conveyor  which  is  made  to 
screen  the  coke  and  drop  it  directly  into  railroad  cars. 

SECTION   VIII. 

THE  BY-PRODUCT  PROCESS  FOR  MANUFACTURING  COKE. 

General  Features  of  the  Process:  The  by-product  process,  being  a 
true  disfillation  process,  involves  the  use  of  retort  ovens.  While  there 
are  many  modifications,  these  ovens  may  be  said  to  consist  essentially  of 
three  main  parts,  namely,  the  coking  chambers,  the  heating  chambers,  and 
the  regenerative  chambers — all  constructed  of  brick.  The  retorts  are 
rectangular  in  shape,  varying  in  general  from  30  to  42  feet  in  length,  from 
6  to  10  feet  in  height,  and  from  17  to  22  inches  in  width,  and  are  built  in 
batteries,  of  from  40  to  90  ovens,  in  which  the  coking  chambers  alternate 
with  the  heating  chambers.  The  coal  is  charged  through  openings  in  the 
top  of  the  oven,  and  the  coke  is  pushed  out  one  end  by  means  of  a  power 
driven  pusher  acting  through  the  other  end.  All  watering  is  done  outside 


BY-PRODUCT  COKE  91 


of  the  oven.  During  the  coking  period,  the  ends  of  the  oven  are  closed 
by  brick  lined  doors,  while  an  opening  in  the  top,  connected  with  suitable 
pipes,  provides  a  means  for  the  escape  of  the  volatile  products  of  the  coal, 
which  must  undergo  several  different  treatments  in  order  to  separate  the 
many  valuable  products.  As  to  the  combustion  chambers,  these  consist 
of  a  great  number  of  flues,  in  order  to  secure  a  uniform  temperature  through- 
out the  entire  length  of  the  oven,  and  may  be  either  of  the  horizontal  flue 
or  of  the  vertical  flue  type.  While  some  of  the  older  ovens  employed  the 
recuperative  principle  for  pre-heating  the  air  for  combustion,  modern 
practice  demands  the  use  of  regenerative  chambers,  because  the  heat  is 
better  conserved  and  less  gas  is  required  thereby  to  operate  the  oven. 
In  the  arrangement  of  these  regenerators,  two  plans  have  been  employed 
with  about  equally  good  results.  By  the  first  plan  the  regenerative 
chambers,  two  in  number,  are  placed  longitudinally  beneath  a  whole  battery 
of  ovens,  but  in  the  second  plan  a  small  regenerator  is  placed  under  each 
end  of  each  oven.  The  latter  has  been  employed  in  the  most  up-to-date 
plants,  because  each  oven  is  thus  made  more  nearly  an  independent  unit, 
and  the  operation  of  the  whole  battery  is  not  liable  to  be  influenced  by  one 
or  two  ovens  that  may  be  shut  down  for  repairs  or  other  reasons. 

Advantages  of  the  By-product  Process:  From  the  brief  description 
given  above,  it  will  be  surmised  that  the  initial  cost  of  a  by-product 
installation  is  very  great.  Nevertheless,  owing  to  its  many  advantages, 
the  method  is  rapidly  becoming  the  leading  process  for  the  production  of 
coke  in  this  country.  These  advantages  as  stated  by  Mr.  Carl  A.  Meissner 
are  as  follows: 

1.  "The  by-product  coke  plant  can  be  constructed  at  or  near  the  blast 

furnaces  which  are  to  consume  its  coke,  and  thus  be  under  the 
same  management. 

2.  It  is  practicable  to  ship  to  it  coking  coals  from  any  section  within 

a  radius  of  a  favorable  freight  rate. 

3.  Many  coals  not  suitable  for   coking  in   beehive   ovens   become 

available  for  by-product  ovens  by  mixing  with  other  coals  and 
are  so  used  to  make  a  first-class  blast  furnace  coke. 

4.  Coking  coals  in  by-product  ovens  permit  of  the  full  recovery  and 

use  of  the  very  valuable  by-products  and  the  gas. 

5.  The  cost  of  making  by-product  coke  at  the  iron  and  steel  works 

is  considerably  less  than  the  cost  of  making  beehive  coke  at  the 
coal  mines  and  transporting  the  coke  to  blast  furnaces,  especially 
when  located  some  distance  away  from  the  beehive  district. 

6.  The  profits  thus  obtained  give  a  substantial  return  on  the  invest- 

ment in  by-product  coke  plants,  large  though  such  investment 
may  at  first  appear." 

The  Plant  of  the  Clairton  By-product  Coke  Company  is  located 
at  Clairton,  Pa.,  in  close  proximity  to  the  Clairton  Steel  Works  and  Fur- 
naces. This  plant  is  the  largest  of  its  kind  in  the  world.  It  consists 


92 


FUELS 


tf 


BY-PRODUCT  COKE  93 


of  two  units,  the  first  of  which  was  completed  in  the  Spring  of  1918.  Each 
unit  consists  of  768  ovens.  The  ovens  are  constructed  in  groups,  or 
batteries,  of  64  ovens  each,  and  in  each  unit  they  are  arranged  in  two 
parallel  rows  of  six  batteries  each.  As  each  oven  has  a  capacity  of  13.3 
net  tons  of  coal,  more  than  25000  tons  of  coal  per  day  are  required  to 
supply  these  two  units  when  coking  on  a  19-hour  schedule.  From 
this  coal  there  are  produced  in  the  neighborhood  of  16,700  net  tons  of  fur- 
nace coke;  500  net  tons  of  domestic  coke;  1,500  net  tons  of  breeze  and 
dust,  which  is  used  to  generate  steam  for  the  plant;  275,000,000  cubic  feet 
of  gas  (average  thermal  value  565  B.  t.  u.),  57  per  cent,  of  which  is  sur- 
plus not  needed  for  heating  the  coke  ovens  at  the  plant  and  therefore 
available  as  fuel  gas  for  the  mills;  285,000  gallons  of  tar;  650,000  pounds 
of  ammonium  sulphate;  68,000  gallons  of  motor  benzol,  or  50,000  gallons 
C.  P.  benzol,  11,500  gallons  C.  P.  toluol  and  10,500  gallons  refined  solvent 
naphthas;  and  10,000  pounds  of  crude  naphthalene.  The  coal  for  the  works 
is  obtained  from  the  mines  of  the  H.  C.  Frick  Coke  Company  in  the  lower 
Connellsville  Field,  and  is  known  commercially  as  Klondike  coal.  These 
mines  are  located  near  the  Monongahela  River,  and  the  coal  is  transported 
from  the  mines  to  the  coke  works  by  water,  for  which  purpose  more  than  180 
barges  of  1,000  tons  capacity  each  and  ten  steamers  are  employed. 

Construction  of  the  Ovens:  The  ovens  of  this  plant  are  known  as 
the  Koppers  500  cubic  feet  by-product  oven.  All  parts  of  these  ovens  are 
constructed  almost  entirely  of  the  best  grade  of  silica  brick.  To  give  the 
coking  chamber  a  volume  of  500  cubic  feet,  each  oven  inside  has  a  length 
of  37  feet  from  face  to  face  of  the  doors,  a  height  of  9  feet  10  inches  from  floor 
to  roof,  and  a  width  that  tapers  from  17  inches  at  the  pusher  end  to  19J£ 
inches  at  the  discharge  end.  Four  "trunnel  heads'*  in  the  top  provide 
means  for  admitting  the  charge,  while  a  separate  opening  at  one  end  provides 
an  outlet  for  volatile  matter.  The  oven  is  of  the  vertical  flue  type  with 
individual  regenerative  chambers.  The  heating  chamber  is  composed  of 
a  total  of  thirty  vertical  flues,  which  rise  from  the  bottom  of  the  chamber, 
where  they  are  provided  with  openings  to  the  regenerative  chambers  and 
to  the  gas  mains,  to  a  large  horizontal  cross-over  flue  on  a  level  a  little  below 
the  top  of  the  coking  chamber.  A  dividing  wall  near  the  middle  of  the  oven 
separates  this  chamber,  except  the  cross-over  flue,  into  two  parts  with 
sixteen  vertical  flues  on  the  narrower  end  of  the  oven  and  fourteen  on  the 
wider  end.  Each  end,  approximately  each  half,  of  the  oven  may  thus  be  heated 
alternately,  and  in  practice  the  reversals  are  made,  automatically  every  half 
hour  for  each  battery  of  sixty-four  ovens,  by  means  of  a  re  versing  motor  con- 
trolled by  an  electrical  clock  attachment.  Two  large  underground  flues, 
one  on  each  side,  extending  along  in  front  of  and  parallel  to  the  battery  and 
connected  to  the  checker  chambers  by  means  of  cast  iron  goose  necks,  furnish 
means  for  the  escape  of  the  products  of  combustion.  These  flues  lead  to 
a  stack,  which  is  located  at  one  end  of  the  battery  and  is  200  feet  high  in 
order  to  furnish  the  draft  necessary  to  draw  the  gases  through  their  tortuous 
course.  An  idea  of  the  magnitude  of  the  structure  may  be  gained  from  the 


94 


FUELS 


fact  that  a  single  battery  of  these  ovens  contains  the  equivalent  of  about 
2,500,000  nine  inch  brick. 


BY-PRODUCT  COKE 


95 


Heating  the  Ovens:     This  construction  may  be  further  explained  by 
tracing  the  course  of  the  gases  when  the  ovens  are  in  operation.      The  air 


-2 

is 

55 


II 


96  -  FUELS 


for  combustion  is  admitted  to  the  checker  chamber  through  a  capped 
opening  on  the  goose  neck  leading  to  the  stack  flue.  From  the  top  of  the 
regenerators  it  is  delivered  through  individual  openings  into  each  of  the 
fourteen  or  sixteen  vertical  flues  on  the  side  of  the  oven  where  the  combustion 
is  to  occur.  Likewise,  the  gas  for  combustion,  which  is  conducted  from  the 
gas  main  into  a  fire  brick  gas  duct  located  below  the  vertical  flues,  is  admitted 
through  individual  fire  brick  nozzles  to  each  of  the  vertical  flues,  about 
10  inches  below  the  air  openings.  Thus,  the  gas  and  air  meet  in  the  flues, 
combustion  occurs,  and  the  hot  waste  gases  are  carried  over  to  the  opposite 
side  of  the  battery  by  the  horizontal  flues,  then  down  the  vertical  flues, 
through  the  checker  work,  out  through  the  goose  neck  and  into  the  large 
flue  that  leads  to  the  stack.  In  order  to  secure  uniform  heating  of  the 
oven  at  all  times,  individual  regulation  of  the  draft  in  each  vertical  flue 
is  provided  by  means  of  a  brick  that  may  be  pushed  out  over  the  top  of 
the  flue  to  reduce  the  size  of  the  opening.  In  the  top  of  the  oven  an  opening, 
which  is  closed  by  a  plug  except  as  occasion  demands  it  to  be  opened,  pro- 
vides access  to  the  sliding  brick  and  also  to  the  gas  nozzle  in  case  it  is 
desired  to  change  the  amount  of  gas  admitted.  The  total  amount  of  air 
admitted  to  each  oven  is  controlled  by  an  adjustable  valve  at  an  opening 
in  the  goose  neck. 

Drying  and  Heating  New  Ovens:  Great  care  is  required  in  preparing 
new  ovens  for  their  first  charge.  This  preparation  is  carried  out  in  two 
stages,  namely,  a  drying  and  a  heating  period,  in  both  of  which  the  tem- 
perature of  the  ovens  must  be  raised  very  slowly  and  uniformly,  in  order 
to  avoid  uneven  expansion  and  consequent  cracking  of  the  brick  work. 
Both  operations  are  carried  out  by  building  fires  in  the  coking  chambers, 
which  are  temporarily  provided  at  each  end  and  near  the  tops  with  a  number 
of  small  holes,  less  than  two  inches  in  diameter,  that  open  into  the  combustion 
chambers  and  thus  furnish  a  passage  for  the  products  of  combustion  through 
the  flues  and  checkers  to  the  stack.  The  drying  operation  is  effected  with 
wood  fires  and  occupies  a  period  of  two  weeks  or  longer,  during  which  time 
the  temperature  of  the  ovens  is  raised  to  250  °F.  Coal  fires  are  then 
substituted  for  the  wood,  and  the  heating  period  is  begun.  About  four 
weeks  are  required  for  this  heating,  during  which  time  the  temperature 
of  the  ovens  is  raised  at  the  rate  of  about  25 °F.  each  day.  The  ovens 
are  then  heated  rapidly  up  to  the  coking  temperature  of  1700°  F  or  more. 
When  available,  gas  may  be  substituted  for  the  wood  and  coal  for  heating 
the  ovens. 

Operation  of  the  Ovens :  Upon  reaching  the  docks  at  the  coke  plant, 
of  which  there  are  two  to  a  unit,  the  coal  is  unloaded  from  the  barges  by 
means  of  grab  buckets  (5  ton)  which  drop  it  into  the  hoppers  of  crushers. 
These  hoppers  are  provided  with  2^-inch  cataract  screens,  so  that  only  that 
portion  of  the  coal  that  is  too  coarse  for  coking  passes  to  the  crushers. 
Here  this  coarse  coal  is  crushed  to  lumps  2J/£  inches,  or  smaller,  in  size,  and 
falls,  together  with  that  from  the  cataract  screen,  upon  a  conveyor  belt 
and  is  carried  to  the  eight  bunkers,  each  of  which  is  located  above  and 


BY-PRODUCT  COKE 


97 


between  two  batteries  of  ovens.     These  bunkers  have  a  capacity  of  4,000 
tons  each,  so  that  four  bunkers  contain,  when  filled,  enough  coal  to  supply 
j  . .  .  .  .  .  .  .  -.  one  unit  for  24  hours.     From  the  bunkers 

*ke  coa^  *s  c^arSe<i  mto  the  ovens  by 
means  of  larry  cars  that  travel  length- 
wise of  the  batteries  and  on  top  of  the 
ovens.  Each  larry  holds  a  single  oven 
charge  of  13.3  tons,  and  is  so  constructed 
that  the  coal  is  measured  both  by  vol- 
ume and  by  weight.  From  the  larry, 
which  has  the  form  of  four  large  funnels, 
the  charge  is  dropped  into  the  oven 
through  the  four  "trunnel  heads,"  the 
doors  of  the  oven  having  been  previously 
set  in  place  and  luted  with  a  mixture  of 
loam  or  clay  and  coke  dust.  A  recipro- 
cating levelling  bar,  carried  on  the  pushing 
machine,  is  then  inserted  through  a  small 
opening  at  the  top  of  the  door  on  the 
narrower  end  of  the  oven,  and  the  peaks 
of  coal  are  levelled  to  a  uniform  depth 
of  9  feet,  thus  filling  the  oven  to  within  10 
inches  of  the  top.  Finally,  all  openings 
to  the  oven  are  closed  and  sealed,  the 
valve  or  damper  to  the  gas  collecting 
main  is  opened,  and  the  coking  process, 
which  lasts  for  a  period  of  19  hours  or 
less,  begins.  The  heat  for  coking  being 
supplied  from  the  heating  chamber  by 
conduction  through  the  walls  of  the  oven, 
coking  proceeds  from  both  sides  of  the 
oven  toward  the  middle,  with  the  result 
that  a  marked  plane  of  cleavage  is 
produced  vertically  down  the  center  of 
the  whole  charge.  This  fact  gives  to 
the  coke  a  short,  block-like  structure 
that  distinguishes  it  from  beehive  coke, 
which,  as  previously  noted,  has  a  long 
columnar  structure.  At  the  end  of  the 
coking  period  the  doors  of  the  ovea  are 
moved  to  one  side  by  mechanical  devices 


Fia.  19.  Ideal  Section  of  the 
By-product  Coke  Oven  Showing 
Structure  of  Coke. 


for  the  purpose,  and  the  coke  is  pushed  out  of  the  oven  from  the  narrower  end 
by  means  of  a  ram  mounted  upon  the  pusher  previously  mentioned.  The 
coke  falls  into  a  side-dump  hopper  car,  is  carried  therein  to  a  quenching,  or 
watering  house,  of  which  there  is  one  at  each  end  of  a  row  of  batteries, 
is  there  watered  by  an  overhead  spray  until  well  blackened,  but  still  hot 


FUELS 


enough  to  dry  itself,  and  is  then  discharged  into  an  inclined  dock  or  bin. 
Here  it  is  allowed  to  become  dry  and  to  cool  somewhat,  after  which  period 
it  is  permitted  to  fall  upon  a  large  belt  conveyor  and  is  carried  up  an  incline 
to  the  screening  house.  The  coke  then  falls  upon  an  incline  screen,  known 
as  the  adjustable  Grizzley  bar  screen.  The  bars  usually  being  adjusted  to 
give  a  1A  inch  opening  at  the  top  and  a  M  inch  opening  at  the  bottom,  the 
furnace  coke  is  separated  from  the  breeze  and  dust  and  drops  into  a  railroad 
car  placed  ready  to  receive  it.  The  material  that  passes  this  screen  may 
be  further  divided  by  rotary  screens  into  dust  and  domestic  coke,  which  is 
also  loaded  directly  into  cars.  At  this  plant  all  the  dust  is  used  under 
boilers  to  generate  steam  for  use  at  the  plant.  The  volatile  products  from 
the  coal  pass  out  of  the  oven  and  are  conducted  through  pipes  to  the  by- 
product plants,  of  which  there  are  two,  one  for  each  unit. 


SECTION   IX. 

THE   BY-PRODUCT  PLANT. 

The  Volatile  Matter  of  Coal  is  a  very  complex  mixture.  It  may  be 
roughly  divided  into  three  classes  of  substances,  based  on  their  state  at 
ordinary  temperatures;  namely,  the  fixed  gases,  or  those  substances  that 
are  gases  at  ordinary  temperatures,  the  liquids,  and  the  solids.  The  fixed 
gases  are  hydrogen,  Ha;  methane,  CH4,  also  known  as  marsh  gas;  ethane, 
C2H6;  propane,  C8H8;  butane,  C4Hi0;  ethylene,  C2H4;  small  amounts  of 
propylene,  C3H6;  butylene,  C4H8;  acetylene,  C2H2;  carbon  dioxide,  CO2; 
carbon  monoxide,  CO;  hydrogen  sulphide,  H2S;  nitrogen,  N2;  oxygen,  O2; 
and  ammonia,  NHs.  The  vapors  that  are  liquid  at  ordinary  temperatures 
are  benzene,  C6H6;  toluene,  C6H5CH3;  xylene,  C6H4  (CH3)2;  carbon  disul- 
phide  CS2;  and  aqueous  vapors.  Among  the  vapors  that  are  solid  at  ordinary 
temperatures,  are  naphthalene,  CioH8;  phenol,  also  known  as  carbolic  acid, 
C6H5OH;  anthracene,  Ci4Hi0;  and  many  others,  all  of  which,  together  with 
heavy  pitch-like  substances,  soot  carbon,  and  small  amounts  of  many  of  the 
more  volatile  liquid  compounds  cited  above,  enter  into  and  make  up  the  tar. 

Gas  Mains  and  Coolers:  All  these  substances  pass  out  of  the  ovens 
through  up-takes  at  their  narrower  ends  and  into  the  U-shaped  gas  collecting 
main  that  extends  above  and  parallel  to  a  battery.  The  gases  and  vapors 
enter  this  collecting  main  at  a  temperature  of  about  400  °C,  and  under 
a  uniform  suction  of  about  .078  inch  (2  mm.)  of  water,  which  is  kept 
constant  by  means  of  a  Northwestern  gage  governor  and  valve.  From 
the  collecting  main  the  gas  is  conducted  by  two  pipes  to  a  large  main, 
known  as  the  suction  main,  which  serves  as  a  common  main  for  one  half  of 
a  row  of  six  batteries.  This  suction  main  leads  to  the  primary  coolers.  In 
passing  through  these  mains,  the  temperature  of  the  gases  drops  to  about 
75 °C,  at  the  inlet  to  the  primary  coolers.  This  reduction  in  temperature 
causes  much  of  the  heavy  tar  vapors  to  condense  in  the  mains,  and  it  is 
found  necessary  to  maintain  a  heavy  stream  of  new  flushing  tar  (composed 


TAR  AND  AMMONIA  99 

of  tar,  50%,  and  ammonia  liquor,  50%),  flowing  through  the  collecting 
mains  to  keep  them  clear  of  pitch  and  carbon  stoppages.  The  require- 
ments for  this  flushing  tar  amount  to  approximately  450  gallons  of  tar  and 
weak  liquor  to  be  circulated  through  the  gas  mains  for  each  ton  of  coal 
carbonized  in  the  ovens.  The  primary  coolers  are  large  rectangular  tanks 
provided  with  tubes  through  wjiich  water  circulates,  while  the  gas,  in  its 
passage  through  the  cooling  chamber,  is  brought  into  intimate  contact 
with  these  pipes.  The  gas  leaves  these  coolers  at  a  temperature  of  about 
32  °C.  The  cooling  of  the  gas  in  its  travel  from  the  ovens  through  the  gas 
mains  and  primary  coolers  results  in  the  condensation  of  about  95  per  cent 
of  all  the  tar  and  water  vapor.  The  condensation  takes  place  about  as 
follows:  50  per  cent  in  the  collecting  mains  and  cross-over  mains,  35  per 
cent  in  the  suction  main,  and  10  per  cent  in  the  primary  coolers.  The  con- 
densing vapors  carry  with  them  all  of  the  fixed  ammonia  in  the  gas  which 
amounts  to  about  15  per  cent,  of  the  total  ammonia. 

Separation  of  the  Tar  and  Ammonia  Liquor:  These  condensed 
liquids,  composed  of  about  70%  tar  and  30%  ammonia  liquor,  are  conducted 
through  pipes  to  two  large  tanks  known  as  the  hot  drain  tanks,  or  tar  wells, 
whence  a  small  portion  is  pumped  back  into  the  gas  mains  as  flushing  tar 
and  the  remainder  to  two  separating  tanks.  In  these  tanks  the  tar  and 
liquor,  the  former  of  which  has  a  specific  gravity  varying  from  1.15  to 
1.17  at  15  °C  while  the  latter  is  little,  if  any,  heavier  than  water,  are  allowed 
to  separate  by  gravity,  when  the  liquor  is  drained  off  into  storage 
tanks  and  the  tar  is  pumped  also  into  storage  tanks.  From  these 
storage  tanks  the  tar,  which  is  composed  of  water,  2%,  pitch,  65%, 
and  heavy  oil,  33%,  and  has  a  heating  value  of  about  16,500  B.  t.  u. 
per  lb.,  is  withdrawn  to  a  small  loading  tank  from  which  it  is  loaded  by 
gravity  into  tank  cars  as  it  is  required  for  shipment;  but  since  the  semi- 
direct  process  for  the  recovery  of  ammonia  is  employed,  the  ammonia 
liquor,  containing  about  1.1%  of  ammonia,  is  pumped  to  ammonia  stills. 
Here,  the  liquor  is  brought  into  contact  with  steam  heated  lime  water, 
which  liberates  the  ammonia.  This  ammonia  gas  is  then  conducted  through 
cast  iron  pipes  back  to  certain  points  in  the  gas  mains,  where  it  is  disposed 
of  in  a  manner  to  be  described  later.  If  desired,  this  ammonia  gas  may  be 
conducted  into  water  to  produce  concentrated  ammonia  liquor.  For  oper- 
ating these  stills  exhaust  steam  from  various  engines  in  the  plant  is  used. 

Compressors  and  Tar  Extractors:  After  the  gas  leaves  the  primary 
coolers,  it  enters  a  number  of  positive  exhausters  (Connersville  Exhausters) 
which  produce  a  suction  of  15  inches  of  water  on  the  entering  side  and 
compress  the  gas  to  a  pressure  equivalent  to  50  inches  of  water  on  the 
discharge  side.  This  pressure  is  required  in  order  to  force  the  gas  through 
the  apparatus  succeeding,  the  first  of  which  are  the  P.  and  A.  (Pelouze 
and  Audouin)  tar  extractors.  In  each  of  these  extractors  the  gas  stream, 
by  means  of  a  perforated  plate,  is  broken  up  into  innumerable  small  jets 
which  impinge  upon  the  cold  surface  of  a  plate  immediately  behind  the 


100  FUELS 


perforated  plate.  The  impact  causes  the  very  fine  particles  of  tar  to  collect 
on  the  impact  plate,  and  the  tar,  thus  accumulating,  runs  off  the  plate  and 
out  of  the  apparatus  through  a  sealed  overflow  at  the  bottom.  In  these 
apparatus  it  is  necessary  to  maintain  a  constant  differential  pressure  of 
about  8  inches  of  water,  and  since  the  holes  in  the  perforated  plate  tend 
to  become  closed  by  the  more  viscous  of  the  tarry  substances,  thus  causing 
an  increase  of  the  pressure,  special  means  must  be  employed  to  overcome 
this  tendency.  At  this  plant  the  desired  result  is  accomplished  by  lower- 
ing the  tar  level  in  the  bottom  of  the  apparatus,  thus  exposing  more  holes 
as  those  in  use  become  clogged.  The  tar  level  is  controlled  by  means  of 
a  pressure  gauge  and  automatic  regulator  attached  to  the  gate  valve 
through  which  the  tar  passes  in  flowing  out  of  the  apparatus.  The  tar 
extracted  by  this  machine  amounts  to  about  5%  of  the  total  tar  originally 
carried  by  the  gas. 

Recovery  of  Ammonia:  The  temperature  of  the  gas,  now  about  38°C., 
having  been  raised  about  6°C.  by  compression  in  the  exhausters,  is  brought 
to  about  66 °C.  by  being  forced  through  preheaters,  which  are  cylindrical 
steel  tanks  containing  steam  coils.  This  preheating  is  necessary  to 
prevent  the  accumulation  of  water  in  the  saturators  and  to  accelerate  the 
reaction,  between  the  ammonia  and  the  dilute  sulphuric  acid,  that  occurs 
in  them.  These  saturators,  of  which  there  are  ten  to  a  unit,  are  large 
lead  lined  steel  pots  containing  a  5%  solution  of  sulphuric  acid,  through 
which  the  gas  is  forced  in  tiny  bubbles.  This  gas,  it  is  to  be  noted, 
contains  all  the  ammonia  recovered  from  the  coal,  for  that  which 
was  liberated  in  the  ammonia  liquor  stills,  previously  described,  has 
been  introduced  into  the  gas  mains  just  after  the  latter  leaves  the 
preheaters.  In  this  way  all  the  ammonia  given  off  by  the  coal  in  coking 
is  brought  into  direct  contact  with  the  dilute  acid,  with  which  it  immedi- 
ately reacts  to  form  ammonium  sulphate,  (NH4)2  SO4.  This  salt  dissolves 
in  the  water  with  which  the  acid  was  diluted,  but,  when  the  baths  become 
saturated,  it  is  precipitated  and  settles  to  the  bottom,  where  it  is  forced 
through  syphon  ejectors  by  means  of  compressed  air  to  elevated  draining 
tables,  also  lead  lined.  From  the  draining  tables,  the  salt  is  periodically 
removed,  placed  in  centrifugal  dryers,  and  whizzed  for  fifteen  minutes, 
which  process  removes  nearly  all  the  water,  the  salt  retaining  about 
2.0%  of  its  own  weight  of  moisture.  The  mother  liquor  derived  from  the 
drying  operations,  as  well  as  the  wash  water  used  to  free  the  crystals  of  the 
slightly  acid  mother  liquor,  flows  back  into  the  saturators,  while  the  salt 
is  scraped  off  the  copper  screen  plates  of  the  centrifugal  machines  with 
wooden  paddles  and  delivered  through  a  chute  to  a  belt  conveyor,  which 
carries  it  to  a  final  dryer,  where  the  moisture  content,  by  means  of  hot 
gases,  may  be  reduced  to  .25%  or  less.  The  final  drying  prevents  caking, 
so  that  the  salt  will  remain  in  a  finely  divided  state  for  indefinite  periods. 
From  the  final  dryer  the  salt  falls  into  a  pit,  from  which  it  is  removed  with 
grab  buckets  to  a  storage  pile,  to  be  shipped  later  as  required. 


BENZOI'  PLANT  101 


Debenzolating  the  Gas:  In  bubbling  through  the  liquid  in  the 
saturator,  the  gas  tends  to  carry  a  little  of  the  acid  along  with  it.  Hence, 
from  the  saturator  the  gas  passes  into  an  acid  separator.  Its  temperature 
here  is  about  54  °C.  which  is  much  too  high  for  the  complete  separation 
of  the  benzene  and  its  homologues.  Therefore,  the  gas  is  put  through  final 
coolers  where  its  temperature  is  lowered  to  30 °C.  These  coolers  are  tall 
steel  towers,  about  100  feet  in  height.  In  them  the  gas  is  brought  into 
direct  contact  with  cold  water,  which  is  introduced  at  the  top,  while  the 
gas  enters  at  the  bottom  and  leaves  at  the  top.  From  these  coolers  the 
gas  is  forced  through  three  benzol,  or  oil,  scrubbers  in  series.  Like  the 
coolers,  these  scrubbers  are  large  steel  towers,  in  which  the  principle  of 
counter  currents  is  employed  throughout.  They  are  filled  with  a  kind  of 
checker  work  of  wooden  slats.  A  product  from  the  refining  of  petroleum,  (or  of 
tar),  known  as  straw  oil  or  wash  oil,  with  a  distilling  temperature  ranging  from 
270  to  370 °C.,  is  sprayed  into  the  top  of  the  washers,  where  it  trickles  down 
over  the  wooden  checker  work  and  is  thus  brought  into  intimate  contact 
with  the  ascending  current  of  gases.  The  oil  absorbs  the  benzene,  toluene, 
xylene,  naphtha  and  naphthalene,  becoming  saturated  to  the  extent  of 
about  3%,  and  removing  92%  or  more  of  the  total  amount  of  these  products 
in  the  gas.  The  entire  removal  of  the  naphthalene  at  this  point  is  of  great 
importance,  because,  if  any  remains  in  the  gas,  it  crystallizes  out  and  clogs 
the  gas  lines.  From  the  scrubbers,  the  oil  carrying  the  benzene,  toluene, 
etc.,  is  pumped  to  the  benzol  plant,  which  serves  both  units  of  the  plant, 
while  the  gas,  now  freed  from  all  except  its  fixed  gases,  is  divided,  half 
being  sent  to  the  fuel  lines  to  heat  up  the  ovens  and  half  to  the  booster 
station,  where  it  is  compressed  by  steam  turbo-blowers  and  delivered  to 
the  mills  as  surplus  gas.  The  loss  in  heating  power  of  the  gas  from  a  given 
quantity  of  coal,  due  to  the  removal  of  the  by-products,  amounts  to  about 

5.8%. 

SECTION   X. 

THE  BENZOL  PLANT. 

Light  Oil:  At  the  benzol  plant  the  wash  oil,  carrying  in  solution  the 
benzene,  naphthalene,  and  their  homologues,  is  first  delivered  to  the  wash 
oil,  or  separating,  stills.  In  order  to  conserve  as  much  heat  as  possible, 
the  inflowing  wash  oil  is  made  to  serve  as  a  condensing  liquid  for  the 
vapors  from  the  still.  After  leaving  the  condensers,  or  heat  exchangers, 
the  oil  passes  to  preheaters,  or  superheaters,  in  which  its  temperature  is 
raised  to  about  145°C.  and  much  of  the  benzol  is  vaporized.  The  oil  then 
passes  to  the  stills,  where  it  comes  into  direct  contact  with  steam  which 
drives  off  the  higher  boiling  oils  and  naphthalene.  Since  the  wash  oil  has 
a  much  higher  boiling  point  than  the  hydrocarbons  it  is  desired  to  recover, 
only  a  small  portion  of  it  escapes  from  the  stills.  The  vapors  from  the 
stills,  passing  into  the  condensers,  or  heat  exchangers,  are  cooled  and  con- 
dense to  form  a  liquid,  known  as  "light  oil,"  which  flows  from  the  bottom 
of  the  condensers  into  storage  tanks.  The  wash  oil,  which  is  not  vapor- 
ized, flows  from  the  bottom  of  the  stills  and  is  conducted  to  heat  exchang- 


102  t  •:•>:.«. FUELS 


ers,  and  then  to  water  coolers  where  its  temperature  is  lowered  to  30°C. 
From  these  coolers  it  is  pumped  back  to  the  oil  scrubbers,  and  can  be  used 
repeatedly.  However,  there  is  a  daily  loss  of  approximately  2%. 

Composition  of  the  Light  Oil:  The  light  oil  is  pumped  from  the 
storage  tank  to  the  crude  still.  The  composition  of  a  light  oil  is  approx- 
imately as  follows: 

Light  Runnings  (benzol  and  carbon  bisulphide).   1.00% 

Pure  Benzol 57.00% 

Pure  Toluol 14.50% 

No.  1  Refined  Solvent  Naphtha 4.50% 

No.  2  Crude  Heavy  Solvent  Naphtha 1.50% 

Crude  Naphthalene 40%  by  weight. 

Wash  Oil 12.00% 

Construction  and  Principles  of  the  Still :  The  crude  still  consists 
of  three  sections.  The  lowest  section  is  a  horizontal  cylinder  provided 
with  steam  coils,  and  has  a  capacity  of  20,000  gallons;  the  second  part, 
called  the  fractionating  column,  is  a  vertical  column  mounted  upon  this 
cylinder  and  composed  of  thirty-one  bell  sections  for  scrubbing  the  vapors 
as  they  pass  upward;  the  third  part,  mounted  on  top  of  the  column  and 
called  the  dephlegmator,  is  a  short  horizontal  cylinder,  that  contains  a 
number  of  water  cooled  pipes  and  acts  as  a  partial  condenser.  The  separa- 
tion of  light  oil  into  its  component  oils  is  effected  by  taking  advantage  of  their 
different  boiling  points.  As  the  temperature  of  the  light  oil  is  raised  and  ap- 
proaches the  boiling  point  of  the  first  runnings,  this  liquid  is  vaporized  and 
passes  up  through  the  columns;  a  portion  of  the  other  oils  with  higher  boiling 
points  is  also  vaporized,  but  is  condensed  before  reaching  the  top  of  the  col- 
umn. There  are  thus  two  movements  in  the  fractionating  column  and  de- 
phlegmator, the  vapors  going  upward  and  the  condensed  oils  flowing  down- 
ward into  the  still.  The  vapors  are  thus  forced  to  pass  through  the  return 
oils  which  aid  in  condensing  the  vaporized  oils  of  higher  boiling  points  and 
permit  only  the  lighter  vaporized  oils  to  reach  the  top  of  the  dephlegmator, 
where  they  are  condensed  and  flow  from  the  still  through  a  manifold  into 
the  storage  tanks.  As  the  temperature  of  the  still  is  further  raised,  the 
benzol,  toluol,  etc.,  is  successively  vaporized  and  condensed,  and  flows  from 
the  still.  However,  it  is  impossible  to  separate  absolutely,  the  benzol  from 
the  toluol,  since,  before  the  benzol  is  completely  driven  over,  some  toluol  will 
be  carried  along  with  it.  It  is  likewise  impossible  to  separate  absolutely  one 
from  another  the  other  constituent  oils.  Hence,  it  is  only  aimed  to  separate 
roughly  the  light  oil  into  what  are  termed  fractions.  These  fractions,  desig- 
nated in  the  order  in  which  they  are  made,  are  as  follows:  Light  Runnings, 
Crude  90%  Benzol,  Crude  90%  Toluol,  Crude  Light  Solvent  Naphtha,  Crude 
Heavy  Solvent  Naphtha  and  Still  Residue.  Each  fraction  is  stored  in  a 
separate  tank. 

Operation  of  the  Crude  Still:  The  details  of  the  operation  of  the 
crude  still  are  as  follows:  20,000  gallons  of  light  oil  are  charged.  The 


BENZOL  PLANT  103 


temperature  is  gradually  raised,  and  approximately  1,600  gallons  of  oil  are 
vaporized  and  condensed.  This  product,  known  as  the  light  runnings  and 
consisting  of  benzol  containing  approximately  3%  carbon  bisulphide,  is 
conducted  into  the  light  runnings  storage  tank.  The  next  product  is  the 
90%  benzol.  The  still  is  continued  on  this  fraction  until  a  test  shows 
30%  by  volume  will  distill  over  at  100°C.  Ninety  per  cent,  toluol  is  then 
collected  until  a  test  shows  that  10%  will  distill  over  at  130°C.  The  next 
product  is  the  light  solvent  naphtha  which  is  collected  until  the  flow  of 
oil  is  very  small,  at  which  point,  and  continuing  throughout  the  operation, 
the  still  is  maintained  under  partial  vacuum.  The  oil  in  this  fraction  is 
collected  until  10%  will  distill  over  at  160°C.,  when  heavy  solvent  naphtha 
is  produced  until  a  test  shows  that  90%  will  distill  over  at  205  °C.  The 
residue  in  the  still,  consisting  of  wash  oil  and  naphthalene,  is  drained  into 
the  naphthalene  pans,  where,  upon  cooling,  the  naphthalene  separates 
as  a  solid.  The  wash  oil  is  removed  by  a  centrifugal  machine,  and 
the  naphthalene  is  washed  with  hot  water.  It  is  sold  as  crude  naphthalene, 
or  refined  and  sold  as  C.  P.  naphthalene. 

Washing  the  Products  of  the  Crude  Stills:  Before  the  products  of 
the  crude  still  are  further  treated  for  the  separation  of  their  component 
oils,  they  are  pumped  to  the  washer  and  there  agitated  with  sulphuric  acid. 
The  object  of  this  treatment  is  to  free  the  oils  from  unsaturated  hydrocarbon 
compounds,  paraffins  and  other  impurities.  These  substances  are  acted 
upon  and  polymerized  by  the  acid,  to  form  substances  that  have  very  high  boil- 
ing points.  Some  of  these  are  insoluble  in  the  oils  and  will  settle  out  with 
the  acid,  forming  a  sludge.  Several  thousand  gallons  of  oil  are  transferred 
to  the  washer  and  66°  Damne"  sulphuric  acid  is  added,  the  proportions  being 
about  920  pounds  of  acid  to  5,000  gallons  oil.  The  contents  of  the  washer 
are  agitated  for  twenty  minutes  and  allowed  to  stand  for  fifteen  minutes, 
when  the  sludge  settles  to  the  bottom  and  is  drawn  off.  This  acid  sludge  is 
then  heated  in  special  pots  with  live  steam,  and  the  acid  thus  separated  from 
the  carbon  aceous  matter,  when  it  is  used  in  the  saturators  to  produce  ammon- 
ium sulphate.  For  the  purest  product  the  oil  is  then  washed  an  additional 
number  of  times  in  the  same  manner.  After  the  use  of  the  acid,  the  oil 
is  washed  with  10%  caustic  soda  solution  until  the  last  trace  of  acid  is 
neutralized.  The  oil  is  then  transferred  to  the  pure  still. 

The  Pure  Stills:  The  construction  and  operation  of  the  pure  still  is 
practically  identical  to  that  of  the  crude  still.  However,  while  the  fractions 
of  the  latter  consist  of  a  mixture  of  oils,  the  pure  still  is  operated  so  that 
one  or  more  fractions  may  be  pure  compounds,  as  is  shown  by  the  following 
data: 

Still  Charge— 17,676  Gals.  Washed  90%  Benzol. 
Fraction.        Time        Gals.  Product. 

1  12%  hrs.       1440     R.    R.     (Rerun)    Benzol— Benzol    containing 

Carbon  Bi-sulphide. 

2  31         "       10950     C.  P.  Benzol. 


104  FUELS 


Fraction.         Time        Gals.  Product. 

3  %  hrs.        790    R.     R.      (Rerun)     Benzol— Greater     portion 

Benzol,  part  Toluol. 

Residue  4496    Principally  Toluol. 

Fraction  2,  being  pure  benzol,  is  not  further  treated,  and  is  ready  for  the 
market.     The  rerun  (R.  R.)  benzol  fraction,  1  and  3,  and  the  residue  are 
stored  in  separate  tanks.     When  a  sufficient  quantity  of  a  R.  R.  fraction 
has   accumulated,    the  pure    still    can  be   charged  with   it   and  a  C.  P. 
(chemically  pure)  product  obtained,  as  is  shown  by  the  following  data: 
Still  Charge— 18,200  Gals. 
R.  R.  Benzol. 
Fraction.        Time       Gals.  Product. 

1  16%  hrs.      2550    R.  R.  Benzol— containing  Carbon  Bisulphide. 

2  39        "       10900    C.  P.  Benzol. 

3  10        "         1750    R.  R.  Benzol— Greater  portion  Benzol,  part 

Toluol. 

4  5        "          650    R.  R.  Toluol— Part  Benzol,  greater  portion 

Toluol. 

5  6K     "         1300    C.  P.  Toluol. 

Residue  1050    Toluol  and  Solvent  Naphtha. 

Fraction  2  and  5  being  C.  P.,  are  ready  for  the  market,  the  other 
fractions  are  stored  and,  when  a  sufficient  amount  is  collected,  are  distilled 
like  the  R.  R.  Benzol  charge  just  described.  It  is  not  essential  that  the 
pure  still  be  charged  with  a  straight  R.  R.,  or  90%  product,  as  a  mixture 
of  the  two  is  often  distilled  as  follows: 

Still  Charge— 6800  Gals.  90%  Washed  Toluol. 

10150       "      R.  R.  Toluol. 
Fraction.       Time.       Gals.  Product. 

1  15M  hrs.       1610    R.  R.  Benzol— greater  portion  Benzol,  part 

Toluol. 

2  29        "         5130    R.  R.  Toluol— greater  portion  Toluol,   part 

Benzol. 

3  24        «         6950    C.  P.  Toluol. 

4  6M  400    R.  R.  Toluol— greater  portion  Toluol,   part 

Naphtha. 

2860    Residue— Toluol  and  Naphtha. 

It  is  thus  apparent  that  the  light  oil  will  eventually  be  completely 
worked  up  into  its  pure  product.  There  is  one  exception,  however,  in  that 
the  light  runnings  containing  the  carbon  bisulphide  cannot  be  separated  by 
fractional  distillation.  The  crude  carbon  bisulphide  benzol  is  the  first 
1600  gallons  that  come  over  ,  in  the  crude  still.  This  is  placed  in  a 
separate  tank,  into  which  the  forerunnings,  or  carbon  bisulphide  benzol, 
from  the  pure  still  is  also  collected.  When  20,000  gallons  of  this  product, 
containing  approximately  3%  carbon  bisulphide,  is  collected,  it  is  placed 


BENZOL,    TOLUOL,   NAPHTHA  105 

in  the  90%  crude  still.  The  first  4000  gallons  condensed  is  benzol 
containing  10%  carbon  bisulphide,  the  remaining  portion  is  90%  benzol, 
which  is  transferred  to  the  crude  90%  benzol  tank.  Only  a  restricted 
market  has  so  far  been  found  for  the  10%  carbon  bisulphide  benzol. 


SECTION   XI. 

SOME   PROPERTIES  AND   USES   OF  THE   RAW 
BY-PRODUCTS  FROM  THE  COKE   WORKS. 

Characteristics  of  Benzol,  Toluol  and  Naphtha:  While  the  names 
benzol,  toluol,  xylol  and  naphtha  are  those  commonly  applied  in  commerce, 
chemical  names  used  to  designate  corresponding  pure  compounds  are 
benzene,  toluene,  xylene,  cumene,  etc.  Naphtha  is  a  mixture  of  several 
compounds,  including  xylene,  cumene  and  others,  so  it  has  no  chemical 
name.  As  previously  indicated,  these  compounds  are  members  of  the 
aromatic,  or  benzene,  series  of  hydrocarbons  represented  by  the  general 
formula  CnH2n  _  e.  The  empirical  formulas  for  benzene,  C6H6,  and  toluene, 
C7H8,  represent  individual  compounds,  but  these  formulas  for  xylene, 
C8Hio,  and  cumene,  C9Hi2,  represent  series  of  isomeric  compounds,  which, 
though  they  are  members  of  the  same  series  and  may  have  the  same  formula, 
differ  widely  in  properties.  Thus  the  formula  CgHio,  may  represent 

CH8  CH3 

6  6 

/  \  /  \ 

orthoxylene   H-C       C-CH3;        metaxylene  H-C       C-H; 

H-C     C-H  H-C      C-CHs 

\  =  \    S 

c  c 

A  it 

CH8  C2H5 

6  fc 

/  \  x  \ 

paraxylene,    H-C      C-H;    or  ethylbenzene,    H-C      C-H. 

H-C     C-H  H-C     C-H 

VV  \  S 

c  c 


The  chief  physical  properties  of  the  first  and  more  important  members 
of  the  series  are  given  in  the  following  table,  which  will  also  give  some 
idea  of  the  method  of  naming  the  compounds: 


106 


FUELS 


Table  13.     Some  Members  of  the  Benzene  Series  and 
Their  Physical  Properties. 


FORMULAS 

NAME 

State  at 
Ordinary 
Temperature 

Melting  or 
Freezing 
Point  °C. 

Boiling 
Point 
°C. 

Specific 
Gravity 

Empirica 

Rational 

C6H6. 
C7H8. 

CgHio 
CgHia  . 

CioHi4 
and  so  o 

CeHe  

Benzene.  .  .  . 

Toluene  or 
Methyl- 
benzene.  .  . 

Ortho  xylene 
or  Ortho- 
dimethyl- 
benzene.  .  . 

Meta-xylene 
or  dimethyl- 
benzene.  .  . 
Para-xylene 
or  dimethyl- 
benzene.  .  .  . 

Ethylbenzene 

Hemimelli- 
thene  or  v  — 
Tri  methyl- 
benzene.  .  .  . 
Pseudocu- 
mene  or 
as-Trimeth- 
ylbenzene.  . 

Mesitylene  or 
s-trimethyl- 
benzene.  .  .  . 

Normal 
Propyl- 
benzene.  .  .  . 

Cumene  or 
Isopropyl- 
benzene.  .  .  . 

Prehitene  or 
Tetra- 
methyl- 
benzene.  .  .  . 

Clear  Liquid 

+5.4 
—92.4 

—28 

—54.8 
+13° 

80.4 
110.3 

142.0 

139.1 
138.0 
136.0 

175.Q 
169.5 
165.0 
159.0 
153.0 

fl5°l 

•-{-} 

-'(-I 
I*"/ 

f  o°1 

-(?} 

•-{-} 

\4°/ 

-{5} 

-{?} 

-{I-:} 

»{?} 

/15°\ 

«(f) 

8Jli!l 
\ff 

CeHs-  CHs  
C6H4.  (CHs)2  .  .  .  . 

\ 

C6H5.  (C2H5)  .... 
C6H8.(CHs)3.... 



C6H5.C3H7  

CeHa-  (CHs)4.  .  .  . 

C6H4.CH3.C3H7.. 
tt  to  C25H44  

Cymene  or 
Methyliso- 
propyl- 
benzene  . 

BENZOL  107 


Commercial  Benzol:  The  term  "benzol"  is  employed  commercially  in 
connection  With  the  various  mixtures  of  the  benzene  hydrocarbons.  Pure 
benzene  is  usually  marketed  as  "Chemically  Pure", or  "C.P.,"  benzol.  The 
mixtures  are  generally  designated  as  90  %  washed  benzol,  90%  crude  benzol, 
80  %  washed  benzol,  80  %  crude  benzol,  and  so  forth.  The  terms  "washed" 
and  "crude  "  denote  whether  or  not  the  product  has  been  washed  with  sulphuric 
acid  to  remove  the  various  unsaturated  compounds  which  are  always  present 
in  the  crude  product.  As  a  rule,  most  of  these  products  are  washed  to  a  greater 
or  less  degree  of  refinement,  according  to  the  purpose  for  which  they  are  required. 
The  terms  "  90  %  "or  "  80  %  "refer  to  the  amount  of-the  fraction  which  will  distil 
over  up  to  100  °C.  The  lower  this  percentage,  the  greater  will  be  the  amounts 
of  toluol  and  solvent  naphthas  present  in  the  product.  The  90%  washed  benzol 
will  contain  approximately  80%  benzol,  15%  toluol,  and  5  %  of  xylols  and  light 
solvent  naphthas. 

Uses  of  Commercial  Benzols:  Benzols  have  been  largely  used  as 
solvents  for  fats,  waxes,  gums,  and  resins.  Mixed  with  alcohol  and  ammonia, 
benzols  of  these  grades  make  an  excellent  cleanser  for  the  removal  of  grease 
and  paint.  Its  solvent  action  on  gums  and  resins  makes  it  a  valuable  substance 
in  the  manufacture  of  paints,  varnishes,  and  lacs,  especially  of  enamel,  bronze 
and  aluminum  paints,  in  which  a  neutral  gum,  or  resin,  is  used  to  form  the 
bases.  The  solvent  action  of  these  grades  upon  rubber  makes  them  valuable 
in  the  preparation  of  cements  and  insulating  varnishes.  They  dissolve  sulphur 
mono-chloride,  and  are  hence  used  in  the  cold  vulcanization  of  rubber.  Heavy 
benzol  and  solvent  naphtha  are  employed  in  the  preparation  of  enamels, 
wood  stains,  varnishes,  and  waterproofing  materials,  such  as  the  rubberized 
cloth  known  as  mackintosh.  Certain  grades  may  be  used  as  a  substitute 
for  turpentine  in  paints  intended  to  cover  resinous  woods.  Naphtha,  in  par- 
ticular, is  important  as  a  rubber  solvent  in  the  manufacture  of  rubber  goods, 
and  as  a  solvent  for  anthracene  during  the  final  purification  of  this  substance 
with  sulphuric  acid.  It  is  also  used  in  the  cleaning  of  clothing. 

Motor  Benzol:  A  product  corresponding  approximately  to  80%  washed 
benzol  makes  an  excellent  motor  fuel  for  automobile  engines,  though  up  until 
1919  it  had  not  been  extensively  used  as  such  in  the  United  States.  Inasmuch 
as  the  commercial  use  of  pure  benzol  and  pure  toluol  is  comparatively  limited, 
since  the  demand  for  explosives  has  decreased,  fully  80%  of  all  the  benzol  and 
toluol  now  produced  in  the  United  States  is  used  as  a  motor  fuel.  For  this 
purpose  there  is  no  necessity  of  separating  the  toluol  from  the  benzol,and  all 
of  these  two  substances,  together  with  practically  all  of  the  xylol,  are  combined 
in  one  product.  This  product  is  marketed  as  "  Motor  Benzol".  Pure  benzol, 
freezing  at  5.4°C.,  congeals  readily  in  cold  weather,  but  the  presence  of  the 
toluol  and  xylol  in  motor  benzol  lowers  this  freezing  point  so  that  cars  may  be 
satisfactorily  operated  during  freezing  weather.  Gasoline  to  the  amount 
of  about  25%  mixed  with  this  product  makes  a  mixture  suitable  for  the  coldest 
weather.  Any  carburetor  adapted  for  gasoline  can  be  used  as  well  for  motor 
benzol,  but  more  air,  or  oxygen,  is  required  in  the  explosive  mixture  with  this 


108 


FUELS 


So.  .03 


Q  o 

O  £    « 

"*          <#°~u\  iS 


£ 

«T 


I 

bfl 
C, 

I 

t/3 


O' 
8*8 


§ 


w  o 

S  a 


§•8 


c;.l 


8T8 


s  -I  ,K  ! 


PURE  BENZOL  109 


fuel  than  with  gasoline.  When  properly  handled,  motor  benzol  gives  from 
20%  to  30%  greater  mileage  than  does  gasoline.  At  the  present  time  motor 
benzol  is  made  under  the  following  specifications: 

Color  Water-  white. 

Distillation  Start  78  °  to  82  °C  . 

Dry     not    higher     than 

135  °C. 

Wash  Test  No  9,  or  better. 

Sulphur  content  not  to  exceed  0.25%  . 

The  wash  test  is  made  by  agitating  equal  quantities,  usually  20  cc., 
of  the  oil  and  pure  sulphuric  acid  in  a  glass  tube  and  comparing  the  color 
with  that  of  numbered  standards,  the  first  of  which,  No.  1,  is  perfectly  clear. 

Properties  and  Uses  of  Pure  Benzol,  or  Benzene  :  The  chief  physical 
properties  of  this  very  interesting  substance  have  already  been  given. 
Concerning  its  chemical  properties  and  uses,  it  may  be  said  that  it  is  one 
of  the  most  interesting  and  useful  compounds  known  to  the  chemical 
profession.  This  fact  is  more  fully  appreciated  when  it  is  known  that  it 
is  the  base  from  which  such  drugs  as  phenol,  hydroquinon,  antipyrin  and 
acetanilid;  such  dye  stuffs  as  resorcinol,  benzidine,  aniline,  and  indigo;  and 
such  explosives  as  nitrobenzol  and  picric  acid  are  prepared.  The  relations 
of  benzene  to  these  compounds  is  best  shown  briefly  by  means  of  some 
such  diagram  as  that  on  the  opposite  page. 

To  illustrate  the  reactions  by  means  of  which  some  of  the  more 
important  compounds  are  derived  from  benzene,  the  following  tables  have 
been  prepared: 

Table  15.     Reactions  Showing  How  Aniline  and  Benzidine  Are 
Derived  from  Benzene. 

(H2  SO4)=C6  H5  NO2+H2  O  ( 
Nitro  Benzene. 


Nitro  Benzene.  Azobenzene. 

C6H5'NO2+6HC1+  3Fe=C6H5-NH2+  3Fe  C12+  2H2O 
Nitro  Benzene.  Aniline. 


Azobenzene.  Benzidine. 

Substantive  Cotton  Dyes. 


110  FUELS 


Table  16.     Reactions  Showing  How  Phenol,  Picric  Aci4  and 
Resorcinol  May  Be  Derived  from  Benzene. 


TT 

CG  Hc+H2  SO4=H2  O    + 


Benzene  Sulphonic  Acid. 


C6  H=    C6H3    +    H20 

Potassium  Benzene  Sulphonate. 


C6  H5>S°3+2KOH=K2  S03+C6H5OK+H20 
(Heated  to  fusion)  Potassium  Phenate; 


2  C6  H5  OK+H2  SO4=2C6  H5OH+K2 
Phenol. 


C6  H5  OH+H2  S04=H2  0 

Phenol.  Para  Benzene  Sulphonic  Acid. 


TT 

OH-C6  H4>S°3+2KOH=K2S°3+H2  0+C6  H4  (OH) 2 

Metadihydroxyl  benzene 

or  Resorcinol 

(Resorcine) 

Base  of  many  colors. 


2C6  H5 

Phenol.  Picric  Acid. 


TOLUENE  111 


Uses  of  Toluene:  One  of  the  chief  uses  of  toluene  is  found  in  the 
manufacture  of  high  explosives.  These  are  prepared  by  nitrating  toluene. 
Both  the  di-nitro-toluene  and  the  tri-nitro-toluene  are  used,  but  of  these 
the  latter,  often  referred  to  as  T.  N.  T.,  is  more  important.  In  intensity 
of  explosion  it  ranks  below  picric  acid,  derived  from  phenol,  but  is  much 
safer  to  handle,  because  the  acid  has  the  property  of  reacting  direct  with 
metals  to  form  picrates,  which  are  very  sensitive  to  shock,  whereas  T.  N.  T. 
does  not  form  dangerous  salts  with  metals  and  is  not  sensitive  to  mechanical 
shock.  It  is  also  replacing  gun  cotton,  or  nitrocellulose,  in  torpedoes,  mines, 
etc. 


CH3 

I 

C 

/  ^ 

O2N-C  C-NOg 

II 

Its  formula  is  represented  thus:       H— C  C— H 

\     ^ 
C 

N02 


Since  the  molecule  of  T.  N.  T.  does  not  contain  enough  oxygen  for 
the  complete  combustion  of  the  carbon  atoms,  it  produces  much  smoke  on 
burning  or  exploding.  This  defect  is  overcome  by  mixing  with  it  some 
nitrate,  preferably  ammonium  or  lead  nitrate.  In  addition  to  its  use  as 
an  explosive,  toluene  is  also  the  base  from  which  saccharin,  benzoic  acid, 
many  dyestuffs,  and  perfumes  are  prepared,  as  a  glance  at  the  accompany- 
ing diagram  will  show:  (See  Table  17.) 

Commercial  Toluol  and  Solvent  Naphtha:  Commerical  toluol, 
often  spoken  of  as  90%  toluol,  is  a  mixture  composed  mainly  of  toluol, 
90%  of  which  will  distill  at  120°C  and  not  more  than  5%  at  100°C.  In  the 
case  of  solvent  naphtha,  90%  distills  at  160°C  and  not  over  5%  at  130°. 
These  mixtures  are  often  used  instead  of  benzol,  because  they  evaporate 
more  slowly  or  because  they  have  a  higher  flash  point.  Some  of  the 
industries  in  which  their  use  is  found  advantageous  are  the  manufacture 
of  automobile  tires,  rubber  cements,  artificial  leather,  wood  stains,  paint 
and  varnish  removers,  paints  (as  a  substitute  for  turpentine)  and  special 
inks. 


112 


FUELS 


w  a  a 


3-g; 


w  **+ 

>*  >» 

M  -^ 
W        0 


33     35 


°-< 


Q  a 


-»t: 


w  a 


z 

5 

i 

w 


a  a 


1!^ 

g^  5 


NAPHTHALENE  113 


Uses  of  Naphthalene:     Ci0H8  does  not  belong  to  the  benzene  series, 
CnH2n— 6,  but  is  the  first  member  of  a  series  represented  by  the  general 

formula  CnH2n — 12,  and  by  the  structural  formula     H     H 

i        i 
C     C 

i\/\ 

H-C     C     C-H 

i       ii       i 
H-C     C     C-H 
\/\  = 
C     C 
I       I 
H     H 


It  is  used  as  an  antiseptic  and  insecticide,  and  is  familiar  to  every  one 
in  the  form  of  moth  balls.  But  its  real  importance  lies  in  the  fact  that 
it  is  the  base  from  which  many  dyestuffs  are  prepared,  chief  of  which  is 
indigo.  The  steps  by  which  this  important  dye  is  derived  from  naphthalene 
are  about  asfollows:  (1)  Naphthalene, Ci0H8, is  heated  with  fuming  sulphuric 
acid  and  mercury,  which  acts  as  a  catalytic  agent,  whereupon  there  is 

formed  phthalic  acid,  C6H4(COOH)2,  (2)  which,  on  being  heated,  passes  into 

CO 

phthalic     anhydride,     C6H4<or.>O      (3)      from      which     phthalimide, 

v/U 

CO 

C6H4<0«>NH,    is    obtained    with    the    aid    of      ammonia    and     heat 
v^O 

(4).  By  oxidizing  phthalimide  with  bleaching  powder,  anthranilic  acid, 
C6H4-NH2-COOH  is  formed,  (5)  which  is  changed  by  treatment  with 
monochloacetic  acid  to  phenyl-glycine-ortho-carboxylic  acid,  C6H4-COOH- 
NH-CH2-COOH,  (6)  By  fusing  this  compound  with  caustic  soda,  indoxyl, 
C2H4NH-CO-CH2,  is  formed  and  is  readily  oxidized  by  the  oxygen  of  the 
air  to  indigotin,  C6H4.NH.CO.C=C.CO.NH.C6H4,  or  indigo-blue.  The 
following  table  will  serve  to  show  the  many  other  dyestuffs  that  may  be 
obtained  from  naphthalene: 


114 


FUELS 


Table  18.     Showing  Some  Products  Derived  from  Naphthalene. 

NAPHTHALENE 

C10H8 


Naphthionic  Acid        Phthalic  Acid     Nitronaphthalene     ce  and  /3  Naphthols 
C«H4<COOH       CioH7N02  Ci0H7OH 


Dye     Indigo      Dye  Explosives       Dye  Stuffs  such  as 
Stuffs  Stuffs  Biebrich   scarlet, 

M  a  r  t  i  u  s      and 
Naphthol  yellow. 


Congo  Red 


Dye 


Tar:  As  obtained  from  gas  works  as  well  as  from  by-product  coke 
plants,  tar  is  a  black,  viscous,  oily  liquid,  with  a  specific  gravity  that  varies 
from  1.15  to  1.20,  that  from  coke  works  having  a  gravity  of  about  1.16. 
It  also  varies  a  great  deal  in  other  respects,  especially  in  composition. 
It  is  a  very  complex  substance;  the  number  of  its  compounds  have 
been  estimated  at  about  300,  only  some  of  which  have  been  isolated  in  the 
laboratory  and  but  a  very  few  in  the  commercial  working  up  of  the  liquid. 
In  the  crude  state  it  may  be  used  as  a  fuel  and  for  road  dressing,  but,  by 
refining,  it  is  made  to  yield  a  great  number  of  products  of  great  economic 
and  hygienic  importance.  The  refining  of  tar  forms  an  industry  by  itself, 
which  requires  volumes  to  describe  in  all  its  details.  Suffice  it  to  say, 
that  the  refining  of  tar  is  essentially  a  process  of  fractional  distillation, 
in  which  it  is  first  separated  roughly  into  several  parts,  which  may 
then  be  further  rectified  into  purer  substances  as  shown  in  the  following 
diagram,  which  is  also  made  to  indicate  the  uses  to  which  the  products 
are  applied. 


COAL  TAR  PRODUCTS 


115 


I 

5 


-I— I 


^Jj. 


1  u 


S  c 

-2 >> 


1 


?! 


£  I*  5  £ 


1 


il 


-* 


I'-ii 


1  r*|J 

iir 

i 


116  AMMONIUM  SULPHATE 

Ammonia,  as  concentrated  ammonia  liquor  (NH4OH  and  H2O),  is 
used  in  making  anhydrous  ammonia  gas  (NH3)  for  refrigeration  purposes 
and  the  aqua  ammonia  of  commerce,  used  for  cleaning.  It  is  also  used  in 
the  manufacture  of  baking  soda  and  a  large  number  of  ammonium  salts, 
such  as  ammonium  chloride  and  ammonium  nitrate.  The  last  named  salt 
is  extensively  used  in  the  manufacture  of  explosives.  By  passing  ammonia 
and  air  over  heated  platinum  black,  the  former  is  oxidized  to  nitric  acid, 
and  large  quantities  of  ammonium  nitrate  are  now  produced  by  this  method. 
Ammonia  is  used  extensively  in  dye  works,  and  a  considerable  amount  is 
consumed  by  chemists  in  analytical  laboratories. 

Ammonium  Sulphate,  (NH4)2SO4,  is  a  white  crystalline  salt,  very 
soluble  in  water  and  easily  decomposed  by  heat,  beginning  at  140°,  into 
NH4HSO4  and  NH3,  and  at  a  red  heat  into  NH8,  SO2  and  H2O.  Unlike 
most  ammonium  salts,  it  cannot  be  sublimed.  As  obtained  from  the  coke 
works,  it  is  slightly  discolored  by  small  amounts  of  various  impurities 
which  it  is  impossible  to  exclude  entirely.  It  is  used  for  a  number  of 
purposes,  including  the  preparation  of  ammonium  persulphate  and  nitrate, 
but  its  great  field  of  usefulness  is  exhibited  as  a  commercial  agricultural 
fertilizer.  William  H.  Childs  of  the  Barrett  Co.  who  has  made  a  careful 
study  of  the  use  of  the  salt  for  this  purpose  speaks  thus  of  it: 

Use  of  Ammonium  Sulphate  as  a  Fertilizer:  "Sulphate  of  ammonia 
is  extensively  used  in  ready  mixed  fertilizers,  which  is  the  form  generally 
purchased  by  the  American  farmer.  These  usually  contain  acid  phosphate 
and  potash,  together  with  sulphate  of  ammonia,  tankage,  cotton-seed  meal, 
etc.  Sulphate  of  ammonia  is  dry  in  its  nature,  and  makes  an  excellent 
mixture  as  far  as  mechanical  condition  goes,  with  the  added  advantage 
that  it  does  not  react  with  the  other  fertilizer  chemicals  to  cause  loss  of 
nitrogen  or  reversion  of  the  acid  phosphate,  both  of  which  points  are  claimed 
against  nitrate  of  soda.  The  nitrogen  in  sulphate  of  ammonia  is  quick  to 
act,  is  not  easily  leached  out  of  the  soil,  and  it  continues  its  action  over  a 
considerable  period,  so  that  the  growing  plant  is  carried  along  to  maturity 
without  setback.  Its  only  disadvantage  is  the  tendency  to  exhaust  the 
lime  in  the  soil.  While  this  point  is  apt  to  be  urged  by  Agricultural  Experi- 
ment Station  men,  it  is  really  of  minor  importance  because  the  actual 
amount  of  sulphate  of  ammonia  in  the  usual  fertilizer  application  is  small, 
and  its  nitrogen  is  relatively  so  much  more  beneficial  to  the  growth  of  the 
crop.  The  liming  of  the  soil,  which,  of  course,  overcomes  all  objections, 
is  urgently  recommended  by  all  Experiment  Station  advisers,  and  in  large 
areas  of  the  Eastern  States  is  practically  the  foundation  of  profitable 
agriculture.  On  the  other  hand,  in  some  soils,  as  in  those  of  Southern 
California  and  parts  of  Texas,  which  tend  to  excess  of  alkali,  the  action 
of  sulphate  of  ammonia  is  peculiarly  beneficial.  In  some  soils  sulphur  is 
lacking,  so  that  the  sulphur  in  sulphate  of  ammonia  actually  acts  as  a 
plant  food." 


FLUXES  117 


CHAPTER  V. 

FLUXES  AND  SLAGS. 

SECTION   I. 

FLUXES. 

Smelting  and  the  Functions  of  a  Flux:  Any  metallurgical  operation 
in  which  the  metal  sought  is  separated,  in  a  state  of  fusion,  from  the 
impurities  with  which  it  may  be  chemically  combined  or  physically  mixed 
is  called  smelting.  Since  botlj  these  conditions  with  regard  to  impurities 
are  usually  present,  smelting  involves  two  processes;  namely,  the  reduction 
of  the  metal  from  its  compounds  and  its  separation  from  the  mechanical 
mixture.  Many  of  these  impurities  may  be  of  a  highly  refractory  nature, 
and  if  they  were  to  remain  unfused,  they  would  choke  up  the  furnace,  retard 
the  separation  of  the  metal  and  interfere  in  various  other  ways  with  the 
smelting.  To  render  such  substances  more  easily  fusible  is  the  primary 
function  of  a  flux.  Again,  some  elements,  being  reduced  almost  simul- 
taneously with  the  metal,  combine  chemically  with  it,  while  other  elements 
and  some  radicals,  chemically  combined  with  the  metal  in  the  raw  materials, 
refuse  to  be  separated  from  it,  except  there  be  present  some  substance  for 
which  they  have  a  greater  chemical  affinity.  To  furnish  a  substance  with 
which  these  elements  and  radicals  may  combine  in  preference  to  the  metal 
is  the  second  function  of  the  flux. 

The  Selection  of  the  Proper  Flux  for  a  Given  Process  is,  then,  chiefly 
a  chemical  problem  and  requires  a  knowledge  of  the  chemical  composition 
of  all  the  materials  entering  into  the  process.  With  this  knowledge  in 
hand,  the  selection  will  be  governed  by  well  known  physical  and  chemical 
laws,  chief  of  which  is  the  action  of  acids  and  bases  toward  each  other 
and  the  fusibility  of  the  various  compounds  thus  formed.  In  general,  if 
the  matter  to  be  fluxed  is  basic,  such  as  lime,  magnesia  and  other  compounds 
of  base  forming  elements,  the  flux  must  be  acid,  while  if  the  impurities  be 
acid,  such  as  silica  and  phosphoric  acid,  a  basic  flux  will  be  required.  In 
most  ores  the  impurities  will  belong  to  both  classes  with  one  or  the  other 
class,  usually  the  acids,  predominating.  In  a  few  iron  ores  the  two  classes 
of  impurities  are  so  well  balanced  as  to  render  the  ores  self-fluxing,  or  by 
proper  mixing  they  can  be  made  so.  In  order  to  control  fusibility,  a  neutral 
flux  is  sometimes  required.  The  cost  of  the  flux  is  also  to  be  considered, 
hence  the  natural  deposits  of  greatest  purity  that  are  easy  of  access  and  in 


118  FLUXES 


close  proximity  to  the  works  are  made  use  of.     A  brief  discussion  of  the 
fluxes  of  greatest  importance  in  the  iron  and  steel  industry  follows: 

Acid  Fluxes:  Silica  is  the  only  substance  that  may  be  classed  as  a 
strictly  acid  flux.  For  this  purpose  it  is  available  as  sand,  gravel  and 
quartz  in  large  quantities  and  in  a  sufficiently  pure  state.  In  blast  furnace 
practice,  it  is  customary  to  employ  acid  open  hearth  or  Bessemer  slags  or 
ores  of  high  silica  content  when  it  is  desired  to  increase  the  acids  in  the 
furnace, as,in  this  way,the  metallic  contents  of  these  substances  are  recovered. 

Alumina:  Unlike  silica,  which  is  a  strong  acid  under  all  conditions, 
alumina  may  perform  either  the  function  of  an  acid  or  a  base,  depending 
upon  the  conditions  imposed.  Thus,  with  silica,  it  forms  aluminum  silicate, 
and  with  a  strong  base,  such  as  sodium,  sodium  aluminate.  A  marked 
peculiarity  is  its  tendency  to  form,  in  conjunction  with  other  bases,  double 
salts  with  polybasic  acids.  As  a  rule,  double  silicates  are  more  easily 
fused  than  those  containing  a  single  base.  Alumina  is  seldom  used  inten- 
tionally as  a  flux,  but  it  is  present  in  nearly  all  raw  material,  hence  unavoid- 
able. 

Basic  Fluxes :  The  chief  natural  fluxes  of  this  class  are  limestone  and 
dolomite.  In  addition,  iron  and  manganese  oxides  act  as  such  in  certain 
processes  where  their  performing  this  function  is  uncontrollable,  as  is  the 
case  in  the  acid  open  hearth.  Referring  to  limestone  and  dolomite  as  blast 
furnace  materials,  there  is  a  difference  of  opinion  among  furnacemen  as  to 
their  relative  value  as  fluxes.  Some  hold  that  limestone  is  the  better, 
while  others  maintain  that  dolomite  gives  as  good,  if  not  better  results, 
their  opinions  usually  being  influenced  by  their  training  and  by  the  extent 
of  their  experience  with  these  materials.  The  presence  of  magnesium  in 
limestone  in  small  amounts  has  little  effect,  but  as  the  content  increases, 
it  may  lower  the  fusion  point  of  the  resultant  slag  by  the  formation  of 
double  salts.  A  high  percentage  (over  3%)  of  magnesia  in  blast  furnace 
slag  renders  it  undesirable  for  cement,  but  for  concrete,  ballast,  etc.,  it  is 
desirable,  as  it  makes  the  slag  harder.  Aside  from  this  objection,  not 
one  of  much  weight,  the  factor  that  governs  the  choice  between  limestone 
and  dolomite  is  the  cost  per  ton  of  available  base. 

Available  Base:  By  available  base  is  meant  the  amount  of  basic 
substance  that  remains  in  the  raw  flux  after  the  acids  of  its  own 
content  are  satisfied.  Referring  to  the  analysis  of  limestones  on  a 
succeeding  page,  it  is  at  once  noticed  that  the  total  is  not  100%.  The 
substance  that  is  missing  is  carbon  dioxide,  which  constitutes  44.0%  of  pure 
calcium  carbonate,  and,  being  evoived  as  a  gas,  is  seldom  determined  in 
making  an  analysis.  Using  the  Bessemer  stone  as  an  example  and 
remembering  that  the  iron  and  phosphorus  are  completely  reduced  in  the 


LIMESTONE  119 


furnace,  we  have  remaining  SiO2,  3.43%;  A12O3,  .86%;  CaO,  51.45%; 
MgO,  1.66%.  If  now,  it  is  desired  to  produce  a  slag  in  which  the 
combined  weight  of  the  bases  (CaO+MgO)  equals  the  silica  and  alumina 
(SiO2+Al2O3)  the  available  v  base=(51.45+1.66)— (3.43+.86)=48.82% 
In  a  similar  manner  the  basic  stone  will  show  52.66%  available  base,  if  it  be 
calculated  on  the  same  slag  basis. 

Limestone,  which  term  also  includes  dolomite  belongs  to  the  sedi- 
mentary class  of  rock-formation  and  is  widely  distributed.  Immense 
deposits  underlie  most  of  the  area  drained  by  the  Ohio  and  Mississippi 
rivers.  The  best  of  these  deposits  are  of  more  ancient  origin  than  our 
coal  beds,  belonging  to  the  Mississippi,  or  early  carboniferous,  period  and 
previous  geological  periods.  Some  limestone  is  formed  by  chemical  pre- 
cipitation, but  the  greatest  portion  of  these  natural  deposits  in  all  prob- 
ability originated  by  the  accumulation  of  the  remains  of  minute  sea  animals. 
During  succeeding  periods  these  deposits  were  covered  to  a  great  depth. 
They  were  later  made  accessible  by  processes  of  uplifting  and  erosion  which 
have  exposed  the  strata  in  places. 

Supply  of  Limestone:  The  main  supply  of  limestone  for  Carnegie 
Steel  Company  comes  from  the  Altoona,  New  Castle,  Martinsburg  and  Butler 
County  districts.  In  the  Altoona  and  Martinsburg  districts  the  beds  have 
been  folded  and  broken  in  the  uplifting  and  lie  at  various  angles,  while  in 
the  other  fields  their  position  is  horizontal  or  nearly  so.  In  all  the  districts 
mentioned  the  ledges  representing  the  various  deposits  vary  in  their  silica  con- 
tent, but  by  aprocess  of  combining  the  stone  from  the  different  ledges,  the  silica 
content  of  the  different  car  loads  is  kept  very  constant,  rarely  exceeding 
5%.  Great  care  is  exercised  to  keep  the  stone  as  free  from  clay  as 
possible,  as  this  is  one  of  the  disturbing  elements  in  uniform  blast  furnace 
operation.  At  most  of  the  quarries,  suitable  crushing  and  screening 
devices  have  been  installed  to  size  the  stone  and  remove  the  more 
silicious  fines. 

Action  of  Limestone  in  Furnaces:  In  the  blast  furnace,  limestone  is 
not  affected,  excepting  for  the  liberation  of  carbonic  acid,  until  the  lower 
levels  and  higher  temperatures  in  the  furnace  are  reached.  In  the  smelting 
zone,  or  the  regions  just  below,  it  combines  with  the  gangue,  forming  slag, 
and  also  unites  with  varying  amounts  of  sulphur  depending  upon  the  con- 
ditions of  temperature  and  basicity  of  the  slag.  Ordinarily,  about  one-half 
ton  of  limestone  is  required  in  the  production  of  one  ton  of  pig  iron.  In 
the  manufacture  of  steel,  it  plays  the  part  of  a  purifying  agent.  Phosphorus, 
in  particular,  cannot  be  removed,  commercially  at  least,  without  it.  Stone 
with  the  lowest  silica  content  is  usually  reserved  for  open  hearth  furnaces, 
that  with  the  lowest  phosphorus  for  furnaces  making  Bessemer  pig  iron, 
while  stones  with  higher  phosphorus  content  are  used  in  furnaces  making 


120  SLAGS 


iron  for  basic  open  hearths.     An  analysis  typical  of  each  of  these  grades  is 
shown  in  the  following  table: 

Table  20.     Representative  Analyses  of  the  Three  Different  Grades 

of  Limestone. 

Open  Hearth  Bessemer  Pig  Basic  Pig 

Silica 80%             3.43%  1.20% 

Iron 10  %                .30  %  .60  % 

Phosphorus 005%                .006%  .033% 

Moisture 10  %                .60  %  .60  % 

Alumina 16%                .86%  .70% 

Lime 54.90%            51.45%  53.88% 

Magnesia 47%              1.66%  .68% 

Neutral  Fluxes :  For  the  purpose  of  making  slags  more  fusible  without 
changing  their  acidity  or  basicity,  neutral  substances  having  very  low 
fusion  points  may  be  used.  This  practice  is  common  in  basic  open  hearths. 
Fluorspar  is  the  substance  generally  used,  though  calcium  chloride  can  be 
substituted. 

SECTION   II. 

SLAGS. 

Slag  is  the  name  applied  to  the  fused  product  formed  by  the  action 
of  the  flux  upon  the  gangue  of  an  ore  and  fuel,  or  upon  the  oxidized  impurities 
in  a  metal.  As  previously  indicated,  it  results  from  the  neutralization  of 
bases  and  acids,  hence  corresponds  to  the  salts  of  wet  chemistry.  The 
word  cinder  is  used  interchangeable  with  slag,  but  cinder  is  also  applied 
to  refuse  in  a  solid  form. 

Functions  of  Slags:  On  account  of  their  fusibility,  chemical  activity, 
dissolving  power,  and  low  density,  slags  furnish  the  means  by  which  the 
impurities  are  separated  from  the  metal  and  removed  from  the  furnace. 
Incidentally,  they  perform  other  important  functions.  Lying  upon  the 
molten  metal,  they  serve  as  a  blanket  to  protect  it  from  the  injurious  action 
of  hot  gases,  and  being  poor  conductors,  they  prevent  over  heating  of  the 
metal  and  at  the  same  time  conserve  its  heat  by  preventing  radiation. 
Since  they  possess  the  power  of  dissolving  oxides,  they  mark  a  sharp  line 
between  reduced  and  unreduced  material,  and  on  this  account  serve  to  keep 
the  metal  clean. 

Importance  of  Slags:  In  the  metallurgy  of  iron,  the  importance  of 
slags  cannot  be  over  emphasized.  In  the  blast  furnace  they  furnish  the 
only  positive  means  of  removing  sulphur,  and,  as  their  fusion  temperature 
varies  with  their  composition,  they  are  one  of  the  means  by  which  hearth 
temperature  is  regulated.  On  this  account,  the  slag  controls  to  the  greatest 
extent  the  quality  of  the  iron  produced.  In  the  open  hearth,  particularly 
in  the  basic  process,  the  slag  is  the  only  means  by  which  the  impurities 


SLAGS  121 


in  pig  iron,  excepting  carbon,  are  removed.  To  the  metallurgist  a  know- 
ledge of  the  properties  of  slags  is  essential.  He  understands  their 
chemical  behavior,  knows  their  formation  temperatures,  fusibility  and 
fluidity,  and  how  to  control  these  factors. 

The  Chemical  Composition  of  Slags  is  within  the  control  of  the 
metallurgist,  and  by  varying  it,  slags  of  almost  any  set  of  properties  desired 
may  be  produced.  Slags  are  mainly  composed  of  two  or  more  silicates  in 
which  other  substances  are  dissolved  or  suspended.  In  the  blast  furnace,  the 
slag  will  consist  principally  of  calcium  silicate,  with  a  part  of  which  the 
magnesium  charged  into  the  furnace  will  be  found  as  a  double  salt.  The 
same  may  also  be  the  case  with  the  small  quantities  of  iron,  manganese, 
and  traces  of  alkali  found  in  these  slags.  The  sulphur  removed  will  be  in  the 
form  of  CaS,  which  dissolves  in  this  mixture.  As  to  the  state  of  alumina, 
which  usually  makes  up  12%  or  more  of  the  slag,  there  is  room  for  doubt. 
By  some  it  is  considered  as  a  base;  by  others,  an  acid.  As  noted  under  the 
heading  of  fluxes,  it  has  the  properties  of  both  an  acid  and  abase.  Hence, 
being  governed  by  the  Law  of  Mass  Action,  it  acts  as  a  stabilizer  to  main- 
tain a  kind  of  equilibrium  between  acids  and  bases.  In  a  highly  silicious 
slag  it  may  side  with  lime  to  form  a  double  silicate,  while  in  a  strongly 
basic  slag  it  takes  the  place  of  silica  in  neutralizing  lime  and  magnesia. 
Since  it  has  very  weak  properties  in  either  direction,  it  seems  reasonable 
to  suppose  that,  in  a  case  where  lime  and  silica  are  in  stable  proportions, 
all  or  a  part  of  the  alumina  may  play  a  neutral  part  and  dissolve  in 
the  slag.  In  ordinary  blast  furnace  practice,  however,  the  sum  of  the 
silica  and  alumina  (SiC^+A^Os)  is  considered  as  the  acid  of  the  slag, 
while  lime  plus  magnesia  (CaO+MgO)  is  taken  to  represent  the  base. 

Relation  of  Acids  to  Bases  in  Blast  Furnace  Slags:  By  chemical 
analysis  of  blast  furnace  slags  it  is  found  that,  usually,  SiO2+Al2O3= 
about  48%  of  the  slag,  the  ratio  of  SiC>2  to  A^Oa  being  about  2:1.  After 
deducting  from  the  lime  enough  to  satisfy  the  sulphur,  the  sum  of  the 
remaining  lime  together  with  the  magnesia  (CaO+MgO)  will  also  be  about 
48%.  This  relation  of  acid  to  base  will  generally  vary  through  a  range  of 
about  2%,  any  increase  in  one  being  followed  by  a  corresponding  decrease 
in  the  other.  The  remaining  4%  to  5%  is  made  up  of  CaS  and  small  amounts 
of  ferrous  and  manganous  oxides.  As  previously  indicated,  the  ratio  of 
lime  to  magnesia  may  vary  somewhat  without  noticeably  affecting  the 
properties  of  the  slag.  The  following  results  of  an  analysis  represent  a 
slag  production  by  a  furnace  making  basic  iron. 

Table  21.  Showing  Relation  of  Acids  to  Bases  in  Blast  Furnace  Slags. 

Acids  Bases 

SiO2      35.02%        CaO      44.03%        FeO         1.16% 

A12O3    14.99"         MgO        2.72 "         MnO        1.08" 

50.01"  46.75"         S  1.35" 


122  SLAGS 


Ratio  of  Acids  to  Bases  in  Open  Hearth  Slags :  Final  basic  open  hearth 
slags  contain  a  much  higher  percentage  of  bases  than  blast  furnace  slags 
and  a  much  lower  percentage  of  acids.  The  lime  and  magnesia  will  always 
be  more  than  twice  the  silica,  alumina  and  phosphorus.  Some  open  hearth 
furnacemen  hold  that  the  best  results  are  obtained  when  the  percentage  f 
of  lime  plus  magnesia  in  the  final  slag  is  three  times  that  of  the  silica.  The 
strong  basic  character  of  basic  slags  is  necessary  for  the  removal  of  phos- 
phorus and  the  small  and  variable  amounts  of  sulphur  possible  by  the 
process.  If  the  percentage  of  lime  is  too  high,  the  slag  will  be  viscous 
and  retard  the  working  of  the  heat.  The  following  analysis  is  the  average 
tapping  slags  from  thirteen  basic  furnaces. 

Table  22.    Relation  of  Acids  to  Bases  in  Basic  Slags. 

Acids,  per  cent.  Bases,  per  cent. 

SiO2  20.74  CaO  40.90 

A12O3  3.55  MgO  9.67 

P2O5  2.85  FeO  10.84 

S  .04  Fe2O3  5.24 

SO3  .23  MnO  5.86 

27.41  72.51 

Acid  to  Base  in  Acid  Furnaces:  Both  in  the  acid  open  hearth  and 
in  the  acid  Bessemer  processes  the  slags  will  consist,  practically,  of  the 
oxides  of  iron  and  manganese  silicates.  In  both  cases  the  silica,  SiO2,  is 
usually  about  50%;  that  in  the  acid  open  hearth  is  seldom  higher  than 
52%  or  lower  than  48%,  while  acid  converter  slag  will  sometimes  contain 
as  high  as  65%.  The  remainder  of  about  50%  will  consist  of  FeO  and 
MnO,  together  with  small  amounts  of  lime  and  magnesia  and  traces  of 
phosphorus  and  sulphur.  Acid  open  hearth  slags  are  self  regulating  as  to 
the  amount  of  FeO  and  MnO.  These  oxides,  in  such  slags,  are  always 
present  in  such  quantities  that  their  combined  percentage  is  equal  to  about 
46%  of  the  slag. 

Electric  Steel  Furnace  Slags:  The  composition  of  these  slags  is 
affected  by  the  kind  of  steel  made  and  the  method  of  refinement  used. 
However,  the  final  slag  of  an  electric  steel,  that  is,  the  slag  formed  near 
the  end  of  the  reducing  period,  should  be  very  basic,  very  low  in  iron  and 
manganese  content  and  show  a  goodly  percentage  of  calcium  carbide.  The 
following  analysis  may  be  considered  as  representing  a  good  average  finish- 
ing slag  for  this  process: 

Silica,  17.90%;  Iron,  .32%;  Lime,  61.51%;  Magnesia,  7.47%;  Manganese, 
.35%;  Sulphur,  1.30%;  Calcium  Carbide,  .51%;  Alumina,  6.00%. 

'Acids  Formed  by  Silicon:  A  study  of  slags  is  facilitated  by  a  study 
of  the  acids  of  silicon.  There  are  a  number  of  these  acids  which  chemists 
consider  as  being  derived  from  orthosilicic  acid,  H4SiO4  or  (H2O)2  SiO2, 


SLAGS  123 


through  the  loss  of  varying  amounts  of  water,  and  are  called  polysilicic 
acids.  When  orthosilicic  acid,  (H^O^-SiOjj,  is  set  free  from  its  salts,  it 
always  forms  H2O-SiO2,  which  is  called,  therefore,  metasilicic  acid  or 
normal  silicic  acid.  The  relations  of  these  various  acids  are  shown  in  the 
following  table: 

Table  23.    Acids  Formed  by  Silicon. 

Orthosilicic  Acid    Metasilicic  Acid    Polysilicic  Acids  Water 

(H2O)2-SiO2 H2O.  SiO2          +    H2O 

2(H20)2Si02  .  /(H20)3.(Si02)2  +    H20 

\   H20    .(Si02)2  H-3H20 

I  (HaO)4-  (Si02)3  -f-  2H20 

3(H20)2Si02 \  (H20)2.  (Si02)3  +  4H20 

{   H2O    .(SiO2)3  +5H2O 

Besides  these  acids,  salts  of  other  acids,  which^do  not  fit  into  this  table, 
are  known  to  exist,  such  as  (H2O)4-SiO2.  By  substituting  bases  like  CaO, 
MgO,  FeO,  MnO,  for  H2O  in  these  formulas,  silicates  such  as  are  formed 
in  slags  would  be  represented.  In  the  case  of  sesquioxides,  as  Fe2O3  and 
Al2Os,  in  which  the  valence  of  the  metal  is-  increased  to  three,  this  sub- 
stitution cannot  be  made  on  a  basis  of  1  for  1,  but  2  for  3,  and  the  formulas 
are,  therefore,  more  complicated. 

So-called  Acid  and  Basic  Slags :  In  substituting  a  base,  such  as  CaO, 
in  the  formulas  above,  it  will  be  observed  that  the  relation  of  base  to  silica 
varies  in  the  different  compounds  through  the  wide  range  from  4  CaO 
combined  with  1  SiO2,  (CaO)4-SiO2,  to  1  CaO  combined  with  3  Si02, 
CaO-(SiO2)3.  The  salts  of  the  meta-and  the  ortho-acids,  (H2O)-SiO2  and 
(H2O)2-SiO2,  in  which,  for  example,  CaO  is  combined  with  1  SiO2,  and 
2  CaO  with  1  SiO2,  appear  to  occupy  positions  of  equilibrium  or  neutrality. 
Any  increase  of 'lime  increases  the  affinity  of  the  slag  for  acids,  whilst  a 
decrease  in  lime  content  causes  the  slag  to  exhibit  acid  properties.  Slags 
of  this  composition  are  also  very  fusible  and  flow  readily. 

Classification  of  Slags:  Some  metallurgists  classify  and  name  the 
slags  derived  from  the  acids  of  silicon  according  to  the  ratio  of  oxygen  in 
the  base  to  oxygen  in  the  acid,  as  shown  in  table  24: 

As  illustrating  the  importance  and  value  of  this  table,  it  is  suffi- 
cient to  say  that  it  is  often  made  the  basis  of  calculation  for  the  theo- 
retical burdening  of  the  blast  furnace.  These  calculations  are  necessary 
in  dealing  with  new  and  unfamiliar  materials  in  order  to  determine  the 
proper  proportion  of  fuel,  ore  and  flux  in  the  charge.  From  the  type  of 
slag  best  suited  to  produce  the  kind  of  iron  desired,  the  oxygen  ratio  is 
fixed  upon,  which  in  turn  determines  the  relation  of  acids  to  bases.  Then, 
with  the  analysis  of  the  raw  materials  in  hand,  the  impurities  in  each  are 


124 


SLAGS 


combined  according  to  this  relation.  As  a  result  of  this  combination  the 
excess  acids  of  fuel  and  ore  are  found,  and  the  available  base  of  the  flux. 
These  quantities,  being  combined  in  accordance  with  the  slag  ratio,  will 
then,  with  the  exception  of  variations  in  fuel  consumption,  fix  the  relations 
of  the  three  materials. 

Table  24.    Method  of  Classifying  Slags. 


Monoxide 
Base 
(CaO)4.SiO2 
(CaO)2.SiO2 
(CaO)4.(SiO2)3 
CaO.SiO2 
(CaO)2.(SiO2)3 

Sesquioxide      Oxygen 
Base            in  Base 

(Al203)4-(Si02)3    2      : 
(Al2O3)2-(SiO2)3    1      : 
(Al2O3)4.(SiO2)9     2      : 
(A1203)  .(Si02)3    1      : 

(Al2O3)2.(SiO2)9    1      : 

Oxygen 
in  Acid    Name 
1     Subsilicate 
1     Monosilicate 
3     Sesquisilicate 
2     Bisilicate 
3    Trisilicate 

Fusibility 
Fusible 
Very  Fusible 
Very  Fusible 
Moderately 
Less  Fusible 

Uses  of  Slags:  While  to  the  metallurgist  slags  represent  refuse  no 
longer  useful  to  his  art,  they  may  be  applied  to  many  purposes.  Railroad 
ballast,  road  building,  roof  covering,  concrete  work,  Portland  cement, 
insulating  materials,  fertilizers,  brick,  and  sand  for  mortar  are  some  of 
the  avenues  open  for  the  economic  disposal  of  slags. 


PIG  IRON  125 


CHAPTER  VI. 

THE  MANUFACTURE  OF  PIG  IRON. 

SECTION   I. 

SOME  INTERESTING   HISTORICAL  FACTS. 

Early  History  of  Iron:1  While  the  sole  purpose  of  this  chapter  is  to 
describe  the  manufacture  of  pig  iron  as  carried  on  at  the  present  time,  one 
or  two  of  the  many  interesting  topics  presented  by  the  historical  aspects 
of  the  subject  will  be  found  pertinent.  A  word  as  to  the  origin  of  the  use 
of  iron  will  serve  to  emphasize  the  process  of  evolution  through  which  this 
wonderful  industry  has  passed  in  attaining  its  present  state  of  advanced 
development.  When  iron  was  first  used,  no  one  knows,  for  that  date  belongs 
to  prehistoric  times.  Archaeological  research  can  only  establish  that  it 
has  been  in  use  by  man  through  a  period  of  about  four  thousand  years. 
Evidence  as  to  the  extent  of  its  use  during  the  first  three  thousand  years 
of  this  period  is  lacking,  but  it  is  very  probable  that  the  metal  was  used 
much  more  extensively  than  the  few  specimens  uncovered  would  indicate. 
The  corrosive  properties  of  iron  make  it,  to  the  archaeologist,  a  perishable 
substance  that  leaves  no  trail. '  If  the  use  of  iron  on  this  continent  were 
to  cease  suddenly  today,  no  evidence  of  its  present  extensive  application 
would  be  expected  a  thousand  years  hence.  Therefore,  only  occasionally 
is  some  implement  or  ornament  found  among  ancient  ruins.  There  is 
doubtful  evidence  of  its  use  by  the  Egyptians  in  building  the  pyramids, 
about  4000  B.  C.  As  to  its  use  by  the  ancient  Hebrews,  by  the  Assyrians 
about  1400  B.  C.,  and,  more  recently,  by  the  Greeks,  there  can  be  no  doubt. 
The  Greeks  were  followed  by  the  Romans  who  became  somewhat  proficient 
in  its  metallurgy.  These  people,  through  their  numerous  and  extensive 
conquests,  the  success  of  which  they  no  doubt  owed  to  the  use  of  metals 
in  making  their  instruments  of  war,  spread  the  art  of  extracting  and 
fashioning  it  throughout  Europe.  Some  knowledge  of  the  metal,  however, 
preceded  them,  for  Caesar,  crossing  the  English  Channel,  found  it  in  use 
among  the  native  Britons.  During  the  Roman  occupation,  the  industry 
grew  to  one  of  importance  in  England.  At  that  time  it  was  obtained  by 
heating  a  mixture  of  ore  and  charcoal,  probably  in  a  flat  bottom  furnace 
or  forge,  until  there  had  collected  a  small  body  of  pasty  metal  which  was  then 
drawn  and  worked  by  hammering  to  make  wrought  iron.  Such,  briefly,  was 
the  process  until  1350,  when  the  iron  makers  of  Central  Europe  succeeded  in 
producing  iron  that  would  melt  in  the  furnace  and  permit  of  casting.  This 
result  they  accomplished  in  a  new  type  of  furnace,  built  of  masonry,  which 
enclosed  a  shaft  or  vertical  opening  in  the  form  of  two  truncated  cones  placed 

JSee  Metallurgy  of  Iron  by  Thomas  Turner,  published  by  Charles  Griffln  and  Co. 
Ltd.,  London. 


126  PIG  IRON 


end  to  end, — in  a  crude  way,  the  lines  of  the  modern  blast  furnace.  The  lower 
frustum  came  to  be  known  as  the  boshes,  the  bottom,  as  the  hearth.  In  this 
furnace,  ore,  flux  and  charcoal  were  charged  in  at  the  top  of  the  furnace,  while 
air,  under  very  low  pressure,  was  blown  in  at  the  bottom.  This  method,  was 
introduced  into  England  about  the  year  1500  where,  in  1619,  coke  was  first  used, 
to  be  followed,  200  years  or  more  later,  by  the  introduction  of  hot  blast. 
In  America  the  first  iron  works  was  established  in  Virginia  on  the  James 
River  in  1619,  and  about  100  years  later  (1710-1715)  the  first  furnace  using 
blast  was  built.  Thence  the  industry  spread,  for  the  most  part,  westward. 

Old  American  Furnaces:  The  furnaces  of  a  period  as  recent  as  one 
hundred  years  ago  were  what  would  now  be  called  very  crude  affairs. 
Portions  of  some  of  them  are  still  standing,  and  one  is  within  a  two  hour 
ride  of  Pittsburgh.  They  were  usually  in  the  form  of  a  truncated  pyramid, 
twenty  to  thirty  feet  high,  and  constructed  of  stone  work  which  enclosed 
a  circular  shaft,  some  four  feet  in  diameter  at  the  top  and  about  eight  feet 
at  the  bosh.  The  hearth  was  either  round  or  square  in  cross  section. 
The  capacity  ranged  from  one  to  six  tons  a  day.  By  the  year  1880,  this  output 
had  been  gradually  increased  to  nearly  100  tons  per  day,  with  a  daily 
coke  consumption  of  nearly  300  tons.  With  all  the  basic  principles  in  use 
for  so  long  a  time,  it  is  remarkable  that  so  little  progress  was  made. 
About  1880,  for  reasons,  which  would  be  too  lengthy  to  explain  here,  very 
rapid  advancement  was  made,  so  that  now  there  are  furnaces  whose  daily 
output  of  pig  iron  exceeds  600  tons  with  a  fuel  consumption  of  less  than 
2000  pounds  of  coke  per  ton  of  iron  produced.  Attention  has  been  called 
to  these  facts  here,  because  it  is  well  to  remember  in  beginning  the  study 
of  the  modern  blast  furnace,  that  the  present  method  for  the  extraction 
of  iron  from  its  ores  represents  a  pyrochemical  process  just  attaining  its 
highest  state  of  development. 

The  Importance  of  Iron:  This  topic  needs  no  comment  here.  Pig 
iron,  besides  being  used  directly  in  the  form  of  castings,  is  the  intermediate 
from  which  all  ferrous  products  are  derived.  Its  importance  is  emphasized 
by  the  reports  of  the  yearly  productions. 

SECTION  II. 
COMPOSITION  AND  CONSTITUTION  OF  PIG  IRON. 

Constitution  of  Pig  Iron:  In  the  solid  form,  pig  iron  represents  a 
very  complex  mixture  made  up  of  uncombined  elements,  chemical  compounds 
and  alloys.  The  amounts  and  relations  of  these  constituents  may  vary 
with  conditions,  so  that  the  complexity  of  the  mixture  does  not  depend 
wholly  upon  the  number  of  elements  present  nor  upon  their  amounts.  Initial 
temperature  and  rate  of  cooling  are  two  of  the  most  important  factors 
affecting  the  properties  of  pig  iron.  These  matters  are  of  great  importance 
when  the  iron  is  to  be  used  for  castings,  and  to  understand  them  fully  requires 
a  very  extended  study  of  the  subject.  This  chapter  has  to  do  mainly  with 
pig  iron  as  an  intermediate  product  in  the  making  of  steel,  so  it  will  be 
most  profitable  to  discuss  only  the  subject  of  its  composition  very  briefly. 


ELEMENTS  IN  127 


Chemical  Elements  in  Pig  Iron:  In  addition  to  iron,  the  elements 
commonly  occurring  in  pig  iron  are  carbon,  silicon,  manganese,  sulphur 
and  phosphorus.  Of  these  elements  iron  will  constitute  91  to  94%,  carbon 
3.0  to  4.0%,  silicon  .50  to  3.00%,  sulphur  less  than  .065%,  and  phosphorus 
.040%  to  2.00%  of  the  whole. 

Carbon  occurs  in  pig  iron  in  two  forms,  called  graphitic  carbon  and 
combined  carbon.  Graphitic  carbon  is  practically  pure  carbon,  existing 
in  the  iron  in  the  form  of  tiny  flakes  which  are  distributed  throughout  the 
mass.  It  forms  in  the  pig  iron  during  the  process  of  cooling,  because  the 
absorbing  power  of  iron  for  carbon  decreases  as  its  temperature  falls. 
Carbon  in  this  form  gives  to  pig  iron  the  grayish  black  appearance  so  often 
seen.  But  in  cooling,  some  of  the  carbon  continues  in  combination  with 
the  iron  as  a  definite  compound,  Fe3C,  93.33%  Fe  and  6.67%  C.  Both 
forms  of  carbon  produce  marked  effects  upon  the  properties  of  the  iron.  The 
tendency  of  the  graphitic  is  to  weaken,  while  the  combined  carbon,  up  to 
the  limit  of  about  .90%,  strengthens  it.  In  Metallography  the  compound 
FesC  is  called  Cementite,  and  to  the  uncombined  iron  is  given  the  term 
Ferrite.  In  cooling  these  two  substances  conduct  themselves  in  a  peculiar 
way  toward  each  other.  In  passing  a  certain  temperature  (about  700°  C.) 
they  arrange  themselves  in  layers  in  the  definite  amounts  of  approximately 
seven  parts  ferrite  to  one  part  cementite.  The  resultant  stratified  segregate 
will,  therefore,  contain  approximately  .85%  C.  Under  the  microscope  these 
stratifications  present  the  appearance  of  mother  of  pearl,  whence  it  is 
named  Pearlite.  Pearlite  is  the  strongest  constituent  of  cast  iron.  When 
heated,  iron  absorbs  carbon,  and  from  the  fusion  point  this  absorption 
becomes  very  rapid.  The  limit,  called  the  saturation  point,  beyond  which 
it  will  not  absorb  any  more,  varys  with  the  temperature,  and  is  also  affected 
by  the  amount  of  silicon  present,  a  rise  in  the  percentage  of  silicon  causing 
a  corresponding  decline  in  the  carbon  content.  Silicon  tends,  also,  to 
decrease  the  combined  carbon,  and  increase  the  graphitic.  Manganese  and 
Chromium  have  the  opposite  effect.  Rapid  cooling  tends  to  prevent  the 
formation  of  pearlite  and  graphite.  In  general,  the  more  rapid  the  cooling 
the  less  the  graphitic  carbon  and  the  greater  the  combined  carbon  content 
will  be. 

Silicon :  In  small  quantities  silicon  has  little  direct  effect  on  pig  iron, 
but  an  increase  above  4%  makes  the  iron  very  brittle,  hence  foundry  iron 
will  seldom  contain  more  than  3%.  In  iron  for  basic  open  hearth  use  the 
percentage  of  silicon  should  not  be  higher  than  1.25,  as  a  high  silicon  content 
tends  to  flux  away  the  lining  of  basic  furnaces  very  rapidly.  For  the  acid 
Bessemer  process  iron  containing  about  1.25%  silicon  is  desirable,  but  the 
content  may  vary  from  1.00%  to  1.50%.  The  oxidation  of  the  silicon 
in  the  Bessemer  process  produces  a  large  quantity  of  heat,  so  that  iron 
containing  a  high  percentage  of  this  element  is  usually  referred  to  as  hot 
iron.  The  amount  reduced  in  the  blast  furnace  is  variable  and  depends  on 
conditions  of  slag  and  temperature.  Its  effect  on  the  carbon  has  just  been 


128  PIG  IRON 


noted.  Since  it  tends  to  throw  the  carbon  out  of  solution,  silicon  is 
used  to  regulate  the  depth  of  chill  in  chilled  castings.  A  content  of  one 
per  cent,  silicon  in  ordinary  low  sulphur  iron  renders  it  difficult  to  obtain 
a  chill.  Below  this  percentage  the  chilling  properties  of  the  iron  are,  roughly 
stated,  in  inverse  ratio  to  the  amount  of  silicon  present.1  Silicon  also 
prevents  blow  holes,  and  tends  to  decrease  the  shrinkage  in  white  irons. 

Manganese  alloys  with  iron  in  all  proportions.  An  alloy  containing 
10  to  25%  manganese  is  called  spiegel.  Alloys  containing  40  to  80%  man- 
ganese are  called  ferro-manganese.  Up  to  one  percent  manganese  tends  to 
strengthen  pig  iron.  It  decreases  the  bad  effects  of  sulphur,  with  which  it 
combines,  replacing  iron.  Its  presence  opposes  that  of  sulphur,  so  that,  with 
uniform  raw  materials,  furnace  conditions  that  give  a  high  percentage  of 
manganese  tend  to  decrease  the  percentage  of  sulphur.  Hence,  in  reason- 
able amounts  of  about  one  per  cent,  it  is  desirable,  especially  for  basic  open 
hearth  use,  where  it  also  aids  in  the  elimination  of  sulphur.  In  Bessemer 
practice  iron  with  a  manganese  content  of  about  .50%  is  desirable.  The  ele- 
ment is  oxidized,  and  unites  with  silica  to  form  a  slag  that  fuses  at  a  com- 
paratively low  temperature  and  is  very  fluid,  so  that  iron  containing  a  high- 
er percentage  than  that  indicated  by  the  latter  figure  gives  rise  to  a  condi- 
tion in  blowing  known  as  a  "sloppy"  heat.  As  to  whether  manganese  has 
a  good  or  a  bad  effect  on  cast  iron,,  there  is  much  difference  of  opinion, 
some  considering  it  almost  as  a  cure  for  all  troubles  and  others 
condemning  it  as  a  source  of  much  trouble,  especially  in  chilled  castings. 
While  it  tends  to  hold  carbon  in  solution,  chill  produced  by  increasing  the 
manganese  content  alone  is  soft  and  tends  to  spall^.  In  moderate  amounts 
it  is  said  to  prevent  cracking  of  the  surface  and  also  spalling  to  some 
extent,  especially  in  chilled  rolls.  Nearly  75%  of  the  total  amount  of 
manganese  charged  into  a  blast  furnace  is  obtained  with  the  metal. 

Sulphur  in  pig  iron  is  generally  supposed  to  be  injurious,  though 
recently  the  statement  that  the  inferior  qualities  exhibited  by  high  sulphur 
iron  is  due  entirely  to  its  presence  has  been  questioned.  Nevertheless,  as 
sulphur  in  steel  is  considered  undesirable  and  as  the  blast  furnace  affords  the 
only  positive  means  of  reducing  it,  pig  iron  containing  less  than  .05%  is 
desirable  for  making  steel  by  all  the  fusion  processes.  Sulphur  with  iron 
forms  iron  sulphide,  which  is  soluble  in  the  metal  and  has  a  melting  point 
that  is  lower  than  the  other  constituents  of  the  iron.  According  to  some 
authorities1,  this  sulphide  in  iron  used  for  castings  has  a  three  fold  influence. 
First,  it  tends  to  hold  the  carbon  in  combined  condition,  hence  can  be 
used  to  increase  the  depth  of  chill  in  chilled  castings;  second,  its  low 
melting  point  causes  it  to  segregate  as  the  iron  solidifies,  thereby  causing 
the  condition  in  castings  known  as  bleeding;  third,  it  increases  the  shrinkage 
of  the  iron  to  a  marked  degree,  thus  increasing  the  difficulty  of  making 
accurate  castings  and  increasing  the  tendency  to  cracks  which  are  a  result 

iSee  The  Principles,  Operation  and  Products  of  the  Blast  Furnace,  by  J.  E. 
Johnson,  Jr.  Published  by  McGraw-Hill  Book  Company  Inc.,  New  York. 


GRADES  OF 


129 


of  the  high  shrinkage.     The  chill  imparted  by  sulphur  is  a  very  hard  one, 
but  is  very  brittle  and  somewhat  unreliable. 

Phosphorus  is  the  only  element  entering  the  blast  furnace  over  which 
the  skill  of  the  furnaceman  has  absolutely  no  control.  Its  compounds  are 
completely  reduced,  so  that  all  the  phosphorus  in  the  raw  materials  is  found 
in  the  metal.  Therefore,  its  content  must  be  regulated  by  proper  selection 
of  raw  materials.  High  phosphorus  causes  a  slight  brittleness  in  pig  iron, 
and  has  a  marked  effect  upon  the  total  carbon.  Ferro-phosphorus  containing 
about  15%  phosphorus  is  carbonless.  Lesser  amounts  permit  a  pro- 
portionate increase  of  carbon,  so  that  the  total  carbon  in  an  iron  containing 
.2%  phosphorus  may  be  as  high  as  4%.  In  this  respect  its  action  is  not 
selective,  since  the  ratio  of  combined  to  graphitic  carbon  is  not  affected. 
Phosphorus  is  known  to  form  a  compound,  FesP,  with  iron,  but  it  is  able 
apparently  to  combine  with  it  in  several  proportions.  Ferro-phosphorus 
containing  as  much  as  25%  phosphorus  is  now  manufactured?  In  iron  for 
casting,  phosphorus  exercises  a  beneficient  effect.  It  tends  to  eliminate 
blow  holes,  decreases  shrinkage,  and  increases  the  fluidity.  Above  .5% 
it  begins  to  weaken  iron,  so  the  amount  used  will  be  governed  by  the  use 
to  which  the  casting  is  to  be  applied. 

Grading  Pig  Iron:  Pig  Iron  is  graded  by  chemical  analysis.  There 
are  several  systems  employed,  many  of  which  are  somewhat  elaborate. 
The  following  table,  which  includes  other  important  blast  furnace  products 
as  well  as  ordinary  pig  iron,  shows  one  of  the  simplest  methods  of  classi- 
fication: 


Table  25.    The  Metallic  Products  of  the  Blast  Furnace. 


RANGE  IN  PERCENT.  OF 


GRADE 

Silicon 

Sulphur 

Phosphorus 

Manganese 

Total  Carbon 

No.  1  Foundry  
No.  2  Foundry  
No.  3  Foundry  
Malleable  Casting.  .  . 
Forge  

2.5  to  3.0 
2.0  to  2.5 
1.5  to  2.0 
.75  to  1.5 
About  1.50 

Under  .036 
.045 
.060 
.050 
1.00 

.25  to  1.00 
.25  to  1.00 
.25  to  1.00 
.2 
1.0 

Under  1.00 
1.00 

•;     i.oo 

"'       1.00 
1.00 

3.50—4.25 
3.50—4.25 
3.50—4.25 
3.50—4.25 
3.50  —  4.25 

Acid  Bessemer  
Basic  Bessemer  
Low  Phos.  Acid  Iron 
Basic  . 

1.00  to  1.50 
Under  1.00 
2.00 
1.25 

.050 
.050 
.030 
.050 

0.  1  or  less 
2.00  to  3.0 
.030 
.100  to  1.00 

About  .50 
Under    .50 
1.00 
1.00  to  2.50 

3.50  —  4.25 
3.50  —  4.25 
3.50—4.25 
3.50  —  4.25 

Spiegel 

About  1  00 

.050 

.150 

18.0  —  22.0 

5.0  —  6.0 

Ferro-Manganese,  .  .  . 
Ferro-Silicon  
Silico-Spiegel  

.50  to  1.00 
8.0  to  15.00 
8.0  to  15.00 

.030 
.070 
.010 

.10  to  .30 
.10  to  .50 
.15 

78.0-82.0 
15.00-20.00 

5.0  —7.0 
1.00—2.00 

130  BLAST  FURNACE 


SECTION   III. 

A   BRIEF   OUTLINE   OF  THE   PROCESS   AND   EQUIPMENT   FOR 
THE   MANUFACTURE   OF  PIG  IRON. 

Trend  of  Modern  Improvements :  With  the  preceding  brief  summary 
of  the  history,  importance,  and  composition  of  pig  iron  in  mind,  the  process 
by  which  it  is  manufactured  furnishes  a  theme  of  great  interest.  Apropos 
of  this  idea,  however,  it  is  to  be  observed  that  a  description  of  the  modern 
methods  of  manufacture  is  rendered  difficult  both  by  the  complexity  of  the 
details  of  the  process  and  by  its  recent  rapid  development.  As  already 
pointed  out,  the  fundamental  principles  have  remained  unchanged  since 
the  founding  of  the  process,  because  experience  has  demonstrated  that  this 
process  is  the  most  practical.  All  improvements,  then,  have  been  made 
with  the  aim  of  increasing  the  production  and  at  the  same  time  decreasing 
the  cost.  These  objects  have  been  attained  to  a  degree  almost  approaching 
perfection  by  the  use  of  materials  of  greatest  purity,  selected  through 
chemical  control,  by  increasing  the  size  of  furnaces,  by  economies  in  fuel 
consumption,  and  by  improved  methods  of  handling  the  materials.  The 
result  is  that  the  small  plants  of  100  years  ago  have  been  succeeded  by 
complex  and  gigantic  affairs.  As  the  greatest  changes  have  been  brought 
about  since  1880,  a  comparatively  recent  date,  the  blast  furnace  plant  is 
just  approaching  the  uniformity  of  perfection.  Furthermore,  since  the 
improvements  have  been  contributed  by  a  great  number  of  men,  it  is  not 
to  be  wondered  at  that  an  inspection  of  the  industry  will  reveal  not  only 
different  stages  of  development  but  also  many  different  methods  of  attaining 
the  same  end.  The  aims  and  fundamental  principles  being  the  same, 
however,  the  numerous  plants,  while  differing  greatly  in  detail,  will  present 
certain  similarities  in  their  gross  features  which  may  profitably  be  reviewed 
before  proceeding  with  the  detailed  description. 

Essentials  of  the  Process:  Essentially,  the  present  process  for  the 
extraction  of  iron  from  its  ores  consists  in  charging  a  mixture  of  ore,  fuel, 
and  flux  in  proper  proportions  through  a  specially  constructed  opening  in 
the  top  of  a  tall  cylindrically  shaped  furnace  called  a  blast  furnace,  while 
heated  air  is  simultaneously  blown  in  near  the  bottom  through  openings, 
called  tuyeres,  the  nitrogen  of  the  air  together  with  the  products  of  com- 
bustion and  reduction  passing  upward  and  escaping  through  openings  at 
the  top.  These  parts  of  the  process,  being  almost  continuous  ones,  are 
accompanied  by  the  periodic  removal  of  a  part  of  the  impurities  in  the 
form  of  slag  at  an  opening  between  the  tuyeres  and  the  bottom,  and  by  a 
like  removal  of  metal  through  a  larger  opening  at  the  bottom.  In  order 
to  carry  out  these  operations  on  the  large  scale  previously  mentioned,  it 
is  evident  that  extensive  equipment  is  required. 

Essential  Equipment:  The  central  feature  in  this  equipment  is  the 
furnace,  which  is  provided  with  apparatus  for  hoisting  the  materials  to  the 
top  and  with  ladles  for  containing  slag  and  molten  metal,  to  which  is  some- 


EQUIPMENT  131 


times  added  casting  beds  or  pig  machines  for  casting  the  metal  into  "pigs" 
of  convenient  size,  and  slag  granulating  pits.  Next  in  importance  follows 
the  blowing  engines  for  producing  the  blast,  then  the  stoves  for  heating 
it.  Of  great  importance  is  the  pumping  station,  the  function  of  which  is 
to  furnish  the  great  quantities  of  water  needed  for  steam,  for  cooling,  etc. 
As  the  gases  that  escape  from  the  top  of  the  furnace  are  combustible, 
apparatus  for  their  most  efficient  disposal  is  desirable.  They  are  used  to 
heat  the  stoves  and  to  generate  power  either  by  burning  them  under  boilers 
or  in  gas  engines,  in  which  case  they  must  be  cleaned  of  the  large  quantities 
of  flue  dust  which  they  carry  out  of  the  furnace.  As  the  moisture  in  the 
air  affects  the  efficiency  of  the  furnace,  some  modern  plants  will  be  provided 
with  apparatus  for  drying  the  blast.  Referring  again  to  the  solid  materials 
of  the  charge,  modern  equipment  requires  a  stock  house,  topped  by  bins, 
in  which  the  ore,  fuel  and  flux  may  be  temporarily  stored  and  conveniently 
removed  for  weighing  or  measuring  before  delivering  it  to  the  hoisting 
device.  Adjacent  to  the  bins  will  be  located  the  stock  yard  containing  the 
ore  pile,  which  is  spanned  by  the  ore  bridges.  A  car  dumper,  advantage- 
ously situated,  will  complete  this  part  of  the  equipment.  Finally,  the  various 
parts  of  the  plant  will  be  made  accessible  by  a  system  of  railways  for  trans- 
porting the  materials. 

SECTION  IV. 

CONSTRUCTION   OF  THE   BLAST   FURNACE   PROPER. 

The  Gross  Features  of  the  Furnace  Proper:  The  modern  blast 
furnace  is  a  tall  circular  structure,  90  to  100  feet  high,  built  of  fire  brick, 
reinforced  externally  by  a  close  fitting  steel  shell  and  encasing  internally 
a  circular  space  of  varying  diameters.  This  space  is  divided  into  three 
main  parts.  The  bottom  section,  called  the  hearth  or  crucible,  is  cylin- 
drical in  form  and  some  10  to  12  feet  deep  in  the  larger  furnaces.  The 
second  section,  having  an  altitude  of  some  12  or  13  feet,  is  called  the  bosh. 
It  is  in  the  form  of  a  frustum  of  a  cone,  which,  in  an  inverted  position,  tops 
the  crucible  with  its  smaller  base.  Setting  above  the  bosh  in  an  upright 
position  with  an  altitude  of  about  70  feet,  is  the  stack.  Formerly  its  outline 
was  also  that  of  a  frustum  of  a  cone,  but  recent  studies  of  furnace  lines 
indicate  that  the  slanting  lines  of  the  cone  should  be  changed  to  the  vertical 
for  a  distance  of  4  or  5  feet  above  the  bosh,  and  for  about  10  feet  from 
the  lower  bell  at  the  top.  The  whole  is  now  capped  by  the  furnace  top, 
which  completes  the  list  of  the  gross  features  of  the  furnace  proper. 

The  Foundation :  Before  proceeding  with  the  details  of  the  parts 
noted  above,  the  foundation  should  be  considered.  In  view  of  the  immense 
weight  which  it  is  required  to  support,  this  part  of  the  furnace  is  of  great 
importance,  because  any  extensive  settling  of  the  furnace  after  it  is  in 
operation  would  result  in  serious  troubles  and  probably  put  it  out  of  com- 
mission. The  depth  of  the  foundation  will  vary  with  the  conditions  of  the 


132  BLAST  FURNACE 


rock  materials  on  which  it  is  to  stand.  If  these  be  sand  .or  clay,  it  may 
be  necessary  to  drive  piling  for  a  depth  of  many  feet,  and  upon  this  begin 
the  foundation.  On  the  other  hand,  if  solid  and  firm  rock  underlies  the 
location  for  the  furnace,  an  excavation  to  this  rock  is  all  that  is  required. 
A  proper  bed  having  been  found  or  otherwise  provided,  the  foundation  is 
started  and  built  up  several  feet  with  concrete,  which-extends  some  distance 
outward  beyond  the  floor  of  the  furnace.  The  remainder  of  the  foundation 
is  then  made  up  of  common  brick  of  good  quality  and  strength,  except  the 
space  directly  beneath  the  hearth  and  walls  of  the  furnace,  where  firebricks 
are  used. 

The  Hearth  or  Crucible  is  the  portion  of  the  furnace  which  serves 
as  a  receptacle  for  the  molten  metal  and  slag.  It  is  constructed  of  fire 
brick  of  the  best  quality;  its  wall  is  usually  sixty  inches  or  more  in  thick- 
ness; and  it  may  be  protected  in  places  with  water  cooled  plates,  if  the  fur- 
nace is  of  recent  construction.  At  the  bottom  the  walls  of  the  hearth  are 
usually  stepped  out  into  the  interior  of  the  hearth  for  four  or  five  courses 
of  brick.  This  construction  gives  the  bottom  surface  a  slight  basin  shape, 
and  tends  to  hold  the  bottom  brick  in  place.  The  hearth  varies  in  diameter 
and  depth  with  the  size  and  capacity  of  the  furnace.  In  the  larger  ones,  it  is 
about  eighteen  feet  in  diameter  and  eleven  feet  deep.  Externally,  it  is 
reinforced  by  a  heavy  metal  jacket  made  of  steel  plates  that  are  riveted 
together,  or  of  iron  castings  in  segments  that  are  jointed  and  bolted  together. 
Jackets  are  always  cooled,  those  of  cast  iron  by  internal  circulating 
systems,  and  those  of  steel  by  external  sprays.  The  upper  diameter  of  this 
jacket  is  smaller  than  the  diameter  at  the  base,  so  that  the  jacket  will 
better  hold  the  walls  of  the  hearth  in  place  by  offering  resistance  in  oppo- 
sition to  the  buoyant  forces  of  the  bath  and  slag. 

The  Bottom  of  the  crucible  is  built  of  fire  brick,  sometimes  in  the 
form  of  large  blocks,  which  are  laid  on  end  with  closely  fitting  joints  in 
order  to  prevent  intrusion  of  metal.  Bottoms  vary  in  thickness  from  about 
six  feet  in  the  smaller  furnaces  to  about  twelve  feet  in  the  large  ones.  The 
bricks  are  almost  entirely  replaced  in  time  by  metal,  which,  collecting  in 
,a  solid  mass,  often  weighing  many  tons,  is  known  as  the  salamander. 

Tapping  Hole :  Situated  at  some  convenient  point  in  the  circumference 
of  the  hearth  and  just  above  the  top  course  of  stepped-in  brick  is  the  tapping 
hole  or  iron  notch.  If  the  bricks  are  not  stepped-in,  the  opening  will  be 
at  the  bottom.  It  may  be  a  square  opening  in  the  brick  about  8x8  inches  or 
an  oblong  or  rectangular  one  6x8  inches  on  the  inside.  The  outside  dimen- 
sions may  be  somewhat  larger  to  permit  of  easily  inserting  the  tapping 
tools.  Proper  provision  is  made  for  the  protection  of  the  hearth  jacket 
at  this  point.  During  the  tapping  of  iron,  the  metal  structures  directly 
above  the  tapping  hole  are  protected  with  a  splasher. 


CONSTRUCTION 


133 


01/5TLE 


FIG.  20.t   Vertical  Section  of  a  modern  Blast  Furnace. 


134  BLAST  FURNACE 


Cinder  Notches:  There  is  usually  but  one  cinder  notch.  This 
opening  may  be  placed  at  any  convenient  point  in  the  circumference  of  the 
hearth  at  a  sufficient  height  above  the  tapping  hole  to  permit  the  collection 
of  the  desired  amount  of  iron  between  tappings.  In  the  larger  furnaces  it 
is  about  six  feet  from  the  floor  of  the  hearth  and  four  to  five  feet  above  the 
tapping  hole,  being  generally  placed  45°  or  90°  from  this  opening.  Unlike 
the  tapping  hole,  this  opening  is  water  cooled  to  protect  the  brick  from  the 
fluxing  action  of  the  slag.  Hence,  the  opening  in  the  brick  work  is  larger, 
being  about  one  foot  in  diameter  inside  and  increasing  to  about  two  feet  on  the 
outside.  In  this  circular  cone-shaped  hole  in  the  brick  the  cooling  devices 
are  placed.  These  are  castings,  usually  made  of  copper,  and  consist  of  acin=> 
der  cooler,  an  intermediate,  or  monkey,  cooler,  and  a  monkey.The  cinder 
cooler  is  in  the  form  of  a  hollow  frustum  of  a  cone.  It  is  about  two  inches 
thick,  and,  between,  its  walls,  proper  provision  is  made  for  the  circulation 
of  water.  It  is  made  to  fit  the  hole  in  the  brick  work  and  is  tamped  securely 
in  place  with  fire  clay.  The  opening  in  this  cooler  is  then  reduced  by 
inserting  into  its  inner  end  the  close-fitting  intermediate  cooler,  which  is 
constructed  like  the  cinder  cooler,  but  smaller  and  shorter.  Finally,  the 
still  smaller  monkey,  through  which  water  circulates  also,  is  inserted, 
reducing  the  opening  to  about  two  inches.  A  short  iron  rod,  called  a  bott, 
tapered  to  fit  the  monkey  and  attached  to  a  long  steel  rod  which  serves 
as  a  handle,  is  used  to  close  the  opening.  The  sizes  of  the  three  coolers 
are  regulated  so  that  the  large  diameters  of  the  monkey  and  intermediate 
cooler  fit  the  smaller  diameters  of  the  intermediate  and  cinder  coolers, 
respectively.  Thus,  the  monkey,  when  in  position,  is  wholly  within  the 
furnace.  In  each  of  these  castings  and  within  their  topmost  quadrant, 
when  in  position  for  service,  are  provided  two  threaded  holes  into  which 
the  pipes  for  ingress  and  egress  of  the  cooling  water  may  be  inserted. 

Tuyeres:  The  tuyeres,  from  ten  to  sixteen  in  number,  are  distributed 
symmetrically  about  the  upper  circumference  of  the  hearth  just  below  the 
boshes.  Their  function  is  to  provide  passages  for  the  blast.  They  also 
determine  the  height  to  which  the  slag  in  the  furnace  may  rise.  In  the 
large  furnaces,  this  height  is  about  three  feet.  Fitted  into  the  opening  in  the 
brick,  flush  with  the  wall,  both  internally  and  externally,  is  the  tuyere 
cooler.  It  is  similar  to  the  cinder  cooler,  and  set  tight  with  fire  clay.  The 
tuyere  itself,  of  copper,  presents  an  internal  diameter  of  from  four  to  seven 
inches,  while  its  external  diameter  is  such  as  to  permit  it  to  fit  snugly  into  the 
smaller  end,  or  nose,  of  the  cooler  and  project  several  inches  into  the  furnace. 
Like  the  cooler,  the  tuyere  is  water  cooled  and  is  tapped  at  two  places  in 
the  top  quadrant  for  the  insertion  of  water  pipes  through  which  a  copious 
stream  of  water  must  be  kept  flowing  to  avoid  burning  it. 

Tuyere  Connections :  With  one  end  fitting  closely  against  the  tuyere, 
is  a  horizontal  cast  iron  pipe,  about  five  feet  long,  called  the  blow  pipe. 
sometimes  the  ' 'belly"  pipe.  Through  it  the  hot  blast  is  delivered  to  the 


CONSTRUCTION  135 


tuyere  from  the  tuyere  stock,  to  which  the  names  leg  pipe,  boot  leg  and 
pen  stock  are  also  often  applied.  The  blow  pipe  may  be  slightly  larger  in 
diameter  at  one  end  than  at  the  other,  and  both  ends  are  turned  to  fit  into 
slight  sockets  in  the  tuyere  and  the  tuyere  stock.  It  is  held  in  place  with 
the  smaller  end  fitting  into  the  tuyere  by  pressure  from  the  tuyere  stock, 
which  is  provided  with  a  spiral  spring  and  connecting  rod,  attached  to  the 
hearth  jacket,  for  this  purpose.  The  tuyere  stock  curves  upward  immedi- 
ately on  leaving  the  blow  pipe,  and  a  hole  in  a  lug  on  its  under  part  gives 
an  opening  through  which  the  connecting  rod  passes  through  the  coiled 
spring  to  the  hearth  jacket  where  it  is  anchored.  The  heavy  spiral  spring, 
which  provides  pressure  and  at  the  same  time  allows  motion  due  to  expan- 
sion and  contraction  of  the  tuyere  stock  and  blow  pipe  with  changes  in 
blast  temperatures,  is  placed  between  this  lug  and  a  large  brass  nut  on  the 
other  end  of  the  connecting  rod.  The  nut  is  made  of  brass  so  it  will  not 
rust  and  be  difficult  to  operate.  In  the  outer  part  of  the  curve  in  the  tuyere 
stock,  and  in  the  center  line  of  the  blow  pipe  and  tuyere  is  a  small  opening, 
closed  by  the  tuyere  cap  or  "wicket,"  through  which  a  small  rod  may 
be  inserted  to  clean  out  the  tuyere  without  removing  the  blow  pipe. 
The  wicket  must  be  of  such  a  form  that  it  may  be  opened  readily  at 
any  time  and  still  be  practically  gas  tight.  To  meet  these  conditions 
the  wicket  is  constructed  on  the  principle  of  the' ball  and  socket  joint. 
The  ball  is  attached  to  the  end  of  the  short  arm  of  a  right  angle  lever  and 
is  held  tightly  in  the  socket  by  a  ball  weight  attached  to  the  long  arm. 
A  smaller  opening,  called  the  peep  hole,  in  the  tuyere  cap  is  covered  with 
glass,  which  permits  inspection  of  that  portion  of  the  interior  of  the  furnace 
directly  in  front  of  the  tuyeres.  Extending  upward,  the  tuyere  stock 
connects  with  the  nozzle  of  the  goose  neck,  to  which  it  is  clamped  by  means 
of  lugs  and  keys  that  fit  into  seats  of  hanging  bars.  The  goose  neck  then 
turns  at  right  angles  and  extends  horizontally  to  the  neck  of  the  bustle 
pipe  to  which  it  is  fitted  and  securely  fastened  by  flanges  and  bolts;  or  the 
tuyere  stock  may  lead  at  an  angle  to  the  horizontal  directly  to  the  lower 
part  of  the  bustle  pipe.  The  bustle  pipe  is  the  large  pipe,  about  four 
feet  in  outside  diameter,  which  encircles  the  furnace  and  distributes  the 
hot  blast  to  the  tuyeres.  All  these  pipes,  down  to  the  blow  pipe,  are 
lined  with  fire  brick.  The  bustle  pipe  is  fed  by  the  hot  blast  main  which 
terminates  at  the  stoves.  It  is  of  about  the  same  size  as  the  bustle  pipe 
and  lined  with  nine  to  twelve  inches  of  fire  brick. 


Boshes:  As  previously  described  the  bosh  is  that  part  of  the  furnace, 
just  over  the  hearth,  where  the  greatest  diameter  is  attained.  No  shell 
cr  jacket  covers  the  exterior  of  the  bosh.  A  standard  bosh  is  constructed 
in  the  following  manner:  Starting  at  the  top  of  the  hearth,  the  brick 
work,  30  inches  in  thickness,  is  stepped  outward,  externally,  nearly  six 
inches  for,  each  twelve  inches  of  vertical  rise.  Each  step-out  is  supported 
by  means  of  a  heavy  steel  band,  or  a  pair  of  bands,  called  bosh  bands. 


136  BLAST  FURNACE 

Inserted  in  the  walls  of  the  boshes,  through  cast  iron  ''boxes,"  placed  in 
the  brick  spaces  between  pairs  of  bosh  bands,  will  be  found  cooling  plates, 
called  the  bosh  plates,  in  horizontal  rows  about  two  feet  apart,  measuring 
vertically.  The  plates  in  each  row  will  be  about  four  or  five  inches  apart, 
and  the  plates  in  the  different  rows  will  be  staggered  vertically,  breaking 
joints  like  brick  work.  This  construction  adds  to  the  cooling  efficiency  of 
the  plates.  There  are  several  different  makes  of  bosh  plates,  but  the  more 
common  ones  will  be  somewhat  wedge-shaped,  with  a  flat  bottom  and  oval 
top,  and  about  four  inches  thick  at  the  point  of  their  greatest  altitude.  They 
are  hollow  and  have  inserted  in  them,  usually  at  opposite  corners,  two 
pipes  through  which  water  flows  continuously.  These  plates  are  necessary 
to  help  protect  the  brick  work,  for,  being  just  above  the  tuyeres  in  the 
zone  of  fusion,  the  bricks  here  receive  the  highest  heat  of  the  furnace. 
Formerly  the  plates  extended  almost  through  the  wall  in  new  work, 
usually  to  within  one  course  of  brick,  but  it  was  found  that  this  course  of 
brick  is  soon  cut  away  after  the  furnace  is  blown  in,  so  now  the  plates 
extend  entirely  through  the  wall  from  the  first. 

Mantle:  At  the  upper  limits  of  the  bosh  is  found  the  mantle,  con- 
forming to  the  shape  of  the  furnace  at  that  point  and  totally  encircling  it. 
The  mantle  is  made  up  of  heavy  steel  plates  and  angles,  upon  which  rests 
the  weight  of  the  stack.  It  is  supported  by  a  series  of  cast  iron  pillars 
or  fabricated  steel  structures,  which  rest  on  foundations  supported  by  the 
main  furnace  foundation.  This  construction  allows  the  entire  bosh  and 
hearth  to  be  removed  without  disturbing  the  rest  of  the  furnace. 

Shaft,  or  Stack,  and  In=Walls:  The  shaft  comprises  all  that  part 
of  the  furnace  which  is  located  above  the  boshes.  The  wall  of  this  shaft  is 
usually,  in  an  imaginary  way,  divided  into  three  almost  equal  parts,  called 
the  upper,  middle  and  lower  inwalls.  Up  to  this  point,  the  construction 
for  all  furnaces  is  fairly  uniform  as  to  general  features.  But  as  to  the 
inwalls  three  types  are  employed,  namely,  the  thick,  the  intermediate, 
and  the  thin  wall.  The  construction  necessarily  differs  for  these  different 
types.  Therefore,  each  type  is  best  described  separately. 

Thick  Wall  Type:  The  inwalls  of  this  type  are  about  five  feet  thick, 
and  are  inclosed  in  a  heavy  riveted  steel  shell  about  one-half  inch  thick. 
The  shell  is  usually  made  oversize  to  provide  a  small  space  between  it  and 
the  brick  work,  in  which  space  is  tamped  lightly  a  packing  of  loam  and 
granulated  slag,  to  allow  for  the  expansion  and  contraction  of  the  inwalls. 
Thick  walled  furnaces  are  seldom  water  cooled  above  the  bosh,  and  their 
walls  furnish  the  sole  support  for  the  top. 

The  Furnace  Lines  and  Bosh  Angles  of  furnaces  of  the  thick  wall 
type  differ  somewhat.  In  modern  blast  furnace  construction  the  lines  of 


CONSTRUCTION  137 


the  furnace,  by  which  is  meant  the  lines  formed  by  the  inner  edges  of  a 
vertical  section  through  the  center,  with  their  enclosed  angles,  are  con- 
sidered of  great  importance.  In  the  old  furnaces,  the  lines  of  the  inwalle 
were  straight,  and  the  boshes  somewhat  flat  with  corresponding  sharp 
angles.  But  with  the  fine  ores  from  the  Lake  Superior  district,  experience 
has  taught  that  much  better  practice  is  obtained  with  more  nearly  vertical 
lines.  So,  in  the  latest  type  of  furnace  the  lower  inwall  will  rise  verti- 
cally for  several  feet,  the  boshes  will  be  steep,  and  the  upper  inwall  will 
drop  vertically  for  a  distance  of  about  ten  feet  from,  the  stock  line.  Bosh 
angles,  that  is,  the  angles  at  the  top  of  the  bosh,  which  its  wall  forms 
with  a  horizontal  from  the  center  of  the  furnace,  are  now  being  increased 
from  about  75°  to  80°.  These  steeper  boshes  are  proving  to  be  an 
important  improvement. 

Intermediate,  or  Setni=Thin,  Wall  Type:  In  the  intermediate  type, 
the  walls  are  about  three  feet  thick,  and  to  protect  the  brick  as  much  as  possible, 
cooling  plates,  similar  to  bosh  plates,  are  inserted  in  the  lower  inwall.  They 
may  extend  for  a  distance  of  from  twenty  to  forty  feet  above  the  bosh. 
The  top  in  this  type  is  sometimes  supported  by  columns  of  fabricated  steel, 
but  in  the  majority  of  cases  it  is  supported  by  the  walls  as  in  the  thick 
walled  type.  The  inwalls  are  surrounded  by  a  steel  jacket  as  in  the  thicker 
type,  the  only  difference  being  in  the  necessary  openings  for  the  coolers. 

Thin  Walled  Type:  In  this  type  the  inwalls  are  from  nine  to  eighteen 
inches  thick,  the  top  is  always  supported  by  structural  work,  and  the  shell  must 
be  cooled  throughout  its  entire  length.  This  cooling  may  be  done  in  three 
ways.  One  method  consists  in  spraying  the  jacket  with  water,  conducted 
through  suitably  arranged  pipes  and  enclosed  by  a  light  "splash  jacket"  which 
conforms  to  the  size  and  shape  of  the  stack.  In  the  second  method  the 
shell  is  encircled  by  a  series  of  deep  and  narrow  horizontal  troughs  through 
which  water  is  kept  flowing  from  the  top  to  the  bottom  of  the  furnace, 
overflowing  from  each  trough  to  the  next  succeeding  lower  one.  Each  of 
three  or  four  of  these  troughs  drain  separately  to  a  common  point  where 
the  temperature  of  the  water  can  be  noted.  In  the  third  type,  the  entire 
outer  surface  of  the  stack  is  kept  covered  with  water  by  means  of  a  spiral 
trough  which,  slightly  separated  from  it,  encircles  the  stack  from  top  to 
bottom.  This  trough  is  kept  full  of  water  by  a  series  of  feed  lines  that  enter 
it  at  various  points  in  the  spiral. 

Furnace  Linings:  The  brick-work  which  forms  the  hearth,  bosh  and 
inwalls  of  a  furnace  are  referred  to  as  its  linings.  All  the  brick  used  in 
the  construction  of  these  parts  are  made  of  fire  clay,  and  are  of  three  kinds, 
known  as  hearth  and  bosh  brick,  inwall  brick  and  top  brick,  each  of 
which  is  made  of  such  materials  and  in  such  a  way  as  to  render  it  best  adapted 
to  the  conditions  it  is  to  be  subjected  to  in  service.  The  hearth  and  bosh 
brick  are  required  to  resist  a  very  high  temperature  and  the  action  of  flux 


138 


BLAST  FURNACE 


and  slag;  inwall  brick  must  be  able  to  withstand  abrasion  at  a  moderately 
high  temperature;  and  top  brick,  always  at  a  comparatively  low  temper- 
ature, must  resist  the  impact  and  abrasive  forces  of  the  charges  as  they 
are  dropped  into  the  furnace.  These  different  qualities  in  the  different 
bricks  are  obtained  by  varying  the  method  of  manufacture  especially  with 
respect  to  composition,  degree  of  grinding  and  temperature  of  burning. 
As  to  the  former  factor,  three  classes  of  materials,  or  clays,  are  available. 
These  are  flint  clay,  plastic  clay  and  calcined  clays.  Mixtures  employed 
by  different  manufacturers  are  by  no  means  uniform,  but  the  following 
may  be  taken  as  fairly  representative  of  good  practice. 


Table  26.     Showing  Data  Relative  to  Fire  Brick  for  Use  in 
Blast  Furnaces. 


PROPORTION  OF 


Kind  of  Brick 

Flint  Clay 

Calcined  Clay 

Plastic  Clay 

Manner  of 
Grinding 

Final 
Temperature 
of  Burning 

Hearth  and 
Bosh  Brick 

50  to  65% 

20  to  35% 

14  to  16% 

Coarse 

1350  °C 

Inwall  Brick 

40% 

30  to  40% 

20  to  30% 

Medium 

to 

Top  Brick.  . 

0  to  30% 

30  to  50% 

40  to  50  % 

Fine 

1450  °C 

All  the  materials,  irrespective  of  the  kind  of  brick,  should  be  and  are 
of  the  best  quality  obtainable,  and  the  brick  are  carefully  inspected  before 
being  put  in  place  in  the  furnace.  The  three  kirfds  of  brick  are  distinctly 
marked  by  the  manufacturer,  so  that  the  danger  of  wrongly  placing  a  brick, 
a  top  brick  in  the  hearth,  for  example,  may  be  avoided.  Great  care  is 
exercised  with  respect  to  brick,  because  the  life  of  the  furnace  depends  in 
a  large  measure  upon  the  lining,  and  the  item  of  cost  for  brick  is  not  a  small 
one.  In  the  construction  of  one  of  the  large  modern  furnaces,  close  to  the 
equivalent  of  800,000  nine  inch  brick  are  required,  and  the  average  con- 
sumption of  brick  is  a  little  more  than  two  brick  for  each  and  every  ton  of 
pig  iron  produced.  Fire  bricks  are  always  laid  in  a  thin  slurry  composed 
of  fire  clay  and  water.  The  slurry  is  applied  by  pouring  it  on  the  top  of 
each  course  with  a  dipper,  and  is  followed  immediately  by  the  next  course  of 
bricks,  which  are  hammered  into  place  to  squeeze  out  all  the  fire  clay  except 
that  required  to  compensate  the  inequalities  of  the  brick. 


CONSTRUCTION  139 


Water  Trough:  Encircling  the  furnace  bosh,  inside  of  and  above  the 
bustle  pipe,  will  be  found  one  or  more  water  troughs  into  which  the  water 
supplying  the  numerous  cooling  plates  is  discharged  in  visible  streams, 
thus  providing  means  of  determining  when  a  plate  is  burned  out.  The 
water,  flowing  from  these  troughs  into  a  well,  may  be  pumped  back  through 
the  cooling  system,  and  thus  be  used  over  and  over. 


Tops:  At  the  present  time  furnace  tops  are  somewhat  complicated 
affairs.  In  olden  times  the  tops  of  furnaces  were  left  open,  the  escaping 
gases  being  allowed  to  burn  in  the  air.  In  the  year  1814,  these  waste  gases 
began  to  be  employed  in  France  for  the  purpose  of  burning  bricks  and  heating 
small  furnaces.  The  first  attempt  to  heat  the  blast  by  utilizing  these  gases 
was  made  in  1834,  and  consisted  in  laying,  across  the  tunnel  head,  pipes 
through  which  the  air  blast  passed  in  going  to  the  tuyeres.  It  was  not 
till  1845  that  a  plan  was  evolved  by  which  the  gases  could  be  used  to  heat 
the  stoves.  To  effect  this  purpose,  changes  in  top  construction  were  neces- 
sary. At  first  the  gases  were  merely  drawn  off  by  the  chimney  draft  of 
the  stoves  through  openings  below  the  stock  line.  The  arrangement, 
known  as  the  bell=and=hopper,  or  cup=and=cone,  was  not  put  into  use 
till  1850.  It  consisted  in  closing  the  top  of  the  furnace  by  means  of  a  large 
circular  hopper,  the  smaller  opening  of  which  was  closed  by  the  bell 
that  could  be  lowered  and  raised  at  will.  With  the  bell  raised  against  the 
hopper,  the  materials  were  dumped  into  the  hopper;  then  the  bell  was  lowered, 
and  the  charge  dropped  into  the  furnace.  As  large  quantities  of  gas  escaped 
with  each  lowering  of  the  bell,  this  device  was  improved  by  the  double- 
bell=and=hopper,  which  is  of  comparatively  recent  origin.  Essentially, 
this  improvement  consisted  in  placing  a  second  but  smaller  bell-and-hopper 
above  the  first,  and  providing  a  gas  tight  space  of  large  size  between  the 
two.  The  raw  material,  upon  being  hoisted  to  the  top,  is  first  dropped  or 
dumped  into  the  upper  hopper,  whence  it  may  fall  into  the  larger  hopper 
below  when  the  small  bell  is  lowered.  The  small  bell  being  raised  against 
ttfe  upper  hopper,  the  large  bell  is  lowered,  and  the  charge  falls  into  the 
furnace  without  the  escape  of  gas.  The  bells  are  made  of  cast  steel,  in  one 
piece,  and  of  such  a  slope,  45°  to  55°,  as  to  permit  the  charge  to  slide  off 
readily.  They  are  usually  supported  from  their  top  centers  by  means  of  a 
rod  and  a  sleeve,  each  attached  to  a  counterbalanced  lever  operated  by 
means  of  a  steam  or  air  cylinder  or  an  electric  motor,  controlled  from  the 
ground.  The  large  bell  is  attached  to  the  rod  and  the  small  bell  to 
the  sleeve.  The  hoppers,  of  cast  steel  or  iron,  will  generally  be  made  up  in 
sections,  which  are  securely  bolted  together.  They  are  provided  with 
a  removable,  but  gas-tight,  flange  and  extension  ring,  also  in  sections, 
which  permit  the  bell  to  be  readily  removed  in  case  a  change  is 
necessary.  The  details  of  this  construction  differ  somewhat  to  conform 
to  the  introduction  of  improvements,  with  the  type  of  hoist,  and  with  the 
ideas  of  the  different  builders. 


140  BLAST  FURNACE 


Stock  Distributor:  One  of  the  alleged  improvements  in  the  bell- 
and-hopper  device  is  that  of  the  stock  distributor.  There  are  several  types 
of  these  distributors  employed,  a  description  of  which  would  not  be  profit- 
able here.  However,  the  object  aimed  at  by  such  devices  may  be  explained 
thus: — It  is  apparent  that,  in  a  mechanically  filled  furnace,  when  the  raw 
materials  are  dropped  into  the  receiving  bell,  the  larger  lumps  of  ore  and 
stone  will  have  a  tendency  to  roll  and  thus  collect  either  around  the  edges 
or  to  one  side  or  the  other.  The  same  things  will  also  happen  upon  dropping 
the  charge  into  the  furnace.  This  tendency  results  in  more  or  less  open 
and  continuous  channels  being  formed  through  the  materials  and  extending 
from  the  top  towards  the  bottom  of  the  stack.  These  channels  offer  less 
resistance  to  the  passage  of  the  blast  than  the  remainder  of  the  materials, 
or  the  fuels,  with  the  result  that  a  disproportinate  quantity  of  gas  passes 
through  them.  This  condition,  called  channelling,  results  in  higher  tem- 
peratures throughout  these  passages,  with  the  consequent  cutting  away  of 
the  walls  where  these  channels  come  in  contact  with  them.  It  is  to  over- 
come this  defect  that  the  various  devices  formerly  mentioned  have  been 
designed. 

Hoisting  Appliances:  The  old  time  method  of  charging  by  hand 
having  been  entirely  superseded  by  automatic  mechanical  charging,  there 
are  now  in  use  two  types  of  these  devices,  namely,  the  skip  hoist  and  the 
bucket  hoist.  In  both  cases  there  is  an  incline,  a  fabricated  steel  structure, 
extending  from  the  top  of  the  furnace  to  or  below  the  bottom  of  the  stock 
house;  and  over  the  tracks  of  this  incline  the  materials  charged  into  the 
furnace  must  pass.  In  the  skip  hoist,  the  conveying  vessel  is  a  small  open- 
ended  steel  car,  called  a  skip,  that  automatically  dumps  the  materials  upon 
the  little  bell-and-hopper.  Skip  hoists  are  generally  provided  with  double 
tracks,  so  that  while  a  loaded  skip  is  passing  up  the  incline  an  empty  one 
is  descending.  In  the  bucket  hoist  the  solid  materials  are  raised  in  a 
bucket,  suspended  from  a  truck  or  carriage,  that  drops  the  charge  into  the 
space  above  the  large  bell  direct.  When  in  position  for  dropping  the  charge, 
the  bucket,  being  itself  provided  with  a  small  bell  at  the  bottom,  takes  the 
place  of  the  little  bell  and  hopper.  During  the  time  the  bucket  is  filling 
at  the  stock  house,  the  opening  left  in  the  top  is  closed  with  a 
special  gas  seal. 

Top  Openings:  The  smallest  opening  in  the  top  of  a  furnace  is  the 
try=hole.  In  operating  a  furnace  it  is  necessary  to  be  able  to  determine 
the  position  of  the  stock  line.  This  is  done  by  means  of  the  stock  indicator, 
which  is  a  rod  of  steel  passing  through  and  fitting  the  try-hole  loosely  so 
that  one  end  rests  upon  the  stock,  while  the  other  is  attached  to  a  small 
steel  cable  that  leads  to  the  stock  house  or  the  cast  house  below.  Some 
stock  indicators  are  automatic  and  self-recording.  For  the  escape  of  the 
gases,  from  two  to  four  large  openings,  called  offtakes,  are  provided.  They 


CONSTRUCTION  HI 


pierce  the  furnace  top  just  beneath  the  large  bell.  From  these  openings, 
about  four  feet  in  diameter,  lead  fire-brick  lined  pipes  which  converge  into 
one  large  pipe  called  the  downcomer  or  downtake.  Into  openings,  either  in 
the  offtake  pipes  or  in  special  openings  in  the  top,  are  inserted  the  explosion 
doors.  These  doors,  located  usually  in  the  ends  of  upright  pipes  arranged 
so  as  to  prevent  ejection  of  material  from  the  furnace,  are  really  valves 
which  are  adjusted,  either  by  weights  or  by  a  mechanical  means,  to  open 
at  a  certain  pressure.  They  are  designed  to  relieve  pressure  and  so  prevent 
possible  injury  to  the  top  by  slips  in  the  furnace.  The  bleeder  is  a  tall 
vertical  pipe,  usually  inserted  on  the  higher  surface  of  the  offtake  pipe 
leading  to  the  downcomer,  to  allow  surplus  gas  to  escape.  It  is  closed 
with  a  valve  on  the  top,  which  opens  automatically,  and  may  also  be 
opened  from  the  ground.  Bleeders  are  usually  lined  with  one  course  of 
fire  brick. 

General  Consideration  for  Top  Construction:  As  previously 
pointed  out,  there  are  many  types  of  top,  and  the  description  above  is 
intended  to  give  a  general  idea  of  the  essential  parts  and  their  uses  only. 
The  chief  endeavor  in  top  construction  is  to  perfect  the  distribution  of  the 
stock  entering  the  furnace  stack,  and  either  eliminate  or  compensate  for 
as  many  irregularities  as  possible.  However,  in  attaining  this  end,  sim- 
plicity must  be  considered,  as  any  great  amount  of  mechanism  on  the  top 
of  a  furnace  is  objectionable.  It  is  important  to  prevent  large  material 
from  being  thrown  out  of  the  furnace  in  case  of  slips,  and  as  little  dust  as 
possible  should  be  carried  out  by  the  gases.  Hence,  in  the  most  recent 
construction,  the  offtakes  enter  vertical  up  takes,  closed  at  the  top  by 
explosion  doors,  and  are  taken  off  the  furnace  as  high  above  the  stock  line 
as  possible,  preferably  at  four  points  equally  spaced  on  the  circumference. 
The  downcomer  connections  are  taken  off  part  way  up  on  these  up-takes. 
In  locating  the  uptakes  in  furnaces  of  most  recent  construction,  care  is 
taken  to  see  that  they  do  not  enter  the  furnace  directly  over  the  tapping 
hole,  cinder  notch,  or  the  entrance  of  the  blast  main  to  the  bustle  pipe, 
because,  these  being  the  most  active  points  in  the  furnace,  this 
arrangement  will  tend  to  give  a  more  even  distribution  of  the  gases 
through  the  stock. 

Runners:  Though  not  given  much  prominence  in  blast  furnace  dis- 
cussions, the  runners,  through  which  the  slag  and  metal  are  carried  away 
from  the  furnace,  constitute  an  essential  part  of  the  furnace  proper.  These 
are  metal  castings  in  the  form  of  deep  troughs  which  are  made  in  sections 
laid  end  to  end  and  buried  so  that  their  top  edges  are  flush  with  the  floor 
of  the  cast  house.  The  trough  leading  from  the  cinder  notch  will,  of  course, 
be  elevated.  It  forms  an  uninterrupted  passage  for  the  slag  from  the  cinder 
notch  to  the  slag  ladle  or  granulating  pit.  The  metal  runner  is  more  com- 
plicated. Beginning  as  a  very  deep  trough  at  the  tapping  hole,  it  is  inter- 
rupted at  the  end  of  about  10  feet  by  the  skimmer,  a  device  for  separating 


142  BLAST  FURNACE 


the  metal  from  the  slag  that  comes  near  the  end  of  a  cast.  There  are 
two  branches  here,  one  for  carrying  away  the  slag  and  another  for  draining 
the  metal  from  this  part  of  the  skimmer  trough  after  the  cast.  From  the 
skimmer  the  main  trough  is  drained  by  branches  leading  to  casting  beds 
on  the  floor  of  the  cast  house,  or  what  is  more  common  now,  to  hot  metal 
ladles  on  a  track  far  enough  below  the  floor  of  the  cast  house  to  permit 
the  metal  to  flow  into  them  from  above.  Before  casting,  these  troughs 
are  given  a  heavy  coating  of  a  loam  or  clay  wash,  which  acts  as  an  insulator, 
protects  the  trough  from  the  hot  metal  and  facilitates  the  subsequent 
cleaning  up.  Without  this  wash  the  hot  metal  would  either  chill  in  the 
trough  or  melt  it  away. 


SECTION   V. 

BLAST  FURNACE   ACCESSORIES. 

The  Stoves,  of  which  there  are  nearly  always  four  to  a  furnace,  are 
first  in  importance  under  the  heading  of  accessories,  being  an  absolute 
necessity  in  modern  blast  furnace  operations.  This  importance  is  due  to 
their  function  of  heating  the  blast.  The  first  stoves  used  were  constructed 
of  iron  pipes  enclosed  in  a  brick  structure  through  which  the  blast  passed 
to  the  furnace,  the  gases  from  the  furnace  being  burned  as  they  circulated 
outside  and  around  these  pipes,  the  recuperative  principle.  Then  it  was 
found  that  the  regenerative  principle  is  much  more  efficient,  so  that  now 
stoves  are  built  entirely  of  brick.  Essentially  they  are  brick  walled  cylin- 
ders, enclosing  a  combustion  chamber  and  a  system  of  regenerative  flues. 
Externally,  the  brick  wall  of  a  stove  is  reinforced  and  supported  by  a  steel 
shell  of  riveted  plates.  The  top  of  the  stove  is  dome-shaped.  Generally, 
the  stoves  are  as  high  and  almost  as  wide  as  the  furnace  itself.  They 
vary  in  size  with  the  size  of  the  furnace.  For  the  largest  furnaces 
they  are  approximately  100  feet  in  height  and  22  feet  in  diameter.  Inter- 
nally, the  combustion  chamber  will  extend  from  the  bottom  to  the  top  of  the 
stove,  and  may  be  located  at  the  center,  in  which  case  they  are  called 
center  combustion  stoves,  or  at  the  circumference,  as  in  side  combustion 
stoves.  The  regenerative  flues  are  filled  with  brick  checker  work,  the 
checkers  being  so  laid  as  to  form  a  system  of  vertical  flues,  from  five  to 
nine  inches  square,  which  extend  from  the  rider  walls  on  the  bottom  to  the 
top  of  the  stove.  The  arrangement  of  the  flues  also  furnishes  a  means  of 
classifying  stoves.  Stoves  in  which  the  gases  from  the  combustion  chamber 
pass  through  only  one  regenerative  flue,  are  called  two=pass  stoves,  while 
in  three=pass  and  four=pass=stoves  they  pass  through  two  and  three 
regenerative  flues,  respectively.  Two-pass  and  three-pass  types  are  the 
most  common.  Since  the  combustible  gases  are  burned  at  the  bottom 
always  of  all  stoves,  it  follows  that  in  two-pass  stoves  the  products  of 
combustion,  passing  through  the  checkers,  must  leave  the  stove  at  the 


STOVES  143 


bottom,  hence  the  opening  to  the  stack  on  two-pass  stoves  is  at  the 
bottom.  At  some  plants,  stoves  of  this  type  are  provided  with  individual 
stacks  which  rise  along  the  side  of  the  stove,  but  in  other  plants  under- 
ground flues  from  a  number,  usually  a  set  of  four,  of  such  stoves  empty 
into  a  single  stack,  centrally  located.  In  the  three-pass  type  the  hot  gases 
are  returned  to  the  top  of  the  stove,  there  to  escape  through  an  opening 
in  the  dome  into  a  stack  which  tops  the  stove. 

Stove  Burners  and  Valves:  Since  the  checkers  in  stoves  are  alter- 
nately heated  by  the  products  of  combustion  of  a  gaseous  fuel  in  their 
passage  to  the  open  and  cooled  by  the  passage  of  the  air  or  blast  in  an 
opposite  direction  and  under  pressure,  a  system  of  burners  and  gas  tight 
valves  are  required.  The  burners  are  usually  very  simple  in  construction, 
consisting  of  a  movable  gooseneck  mounted  on  a  rack  attached  to  the 
terminal  of  a  vertical  section  of  an  underground  gas  flue  in  such  a  manner 
that  the  horizontal  portion  extends  into  a  gas  port  in  the  side  of  the  stove. 
A  plate,  or  valve  cover,  is  attached  to  the  base  of  the  goose-neck  or  the  rack, 
so  that  racking  the  goose-neck  back  and  forward  automatically  closes  and 
opens  the  connection  to  the  gas  main.  There  are  a  number  of  moie  com- 
plicated and  patented  burners  in  use,  which  aim  to  increase  the  efficiency 
of  the  stove1.  The  valves  present  such  a  variety  of  forms  that  a  detailed 
description  of  all  cannot  be  attempted.  The  essential  ones  are  named 
from  their  location.  The  gas  valve  has  already  been  described  in  con- 
nection with  the  burner.  The  chimney  valve  is  located  at  the  base  of  the 
stack,  its  office  being  to  prevent  the  escape  of  air  through  that  opening 
when  the  stove  is  on  blast.  In  three-pass  stoves  this  valve  is  controlled 
from  the  ground  by  means  of  chain,  or  cable,  and  pulleys.  The  cold  blast 
valve  is  located  in  the  air  line,  which  branches  from  the  cold  main  from 
the  blowing  engines  at  a  point  just  ahead  of  its  entrance  into  the  stove. 
As  it  is  never  subject  to  high  temperatures,  an  ordinary  form  of  gate  valve 
may  be  used.  In  the  three-pass  type  of  stove  this  valve  will  also  be  at 
the  top.  The  hot  blast  valve  controls  the  exit  of  the  blast  from  the  stove 
through  which  the  air  passes.  The  blast  being  highly  heated  at  this 
point,  the  hot  blast  valve  must  be  constructed  to  withstand  high 
temperature.  It  is  usually  of  the  mush-room  type,  and  water  cooled. 

Other  Stove  Openings:  Besides  the  openings  mentioned  above,  the 
stove  will  be  provided  with  a  blow  off  valve  to  relieve  the  pressure  and 
provide  partial  escape  of  air  on  changing  the  stove  from  air  to  gas.  This 
valve  may  also  regulate  the  admission  of  air  for  combustion.  Numerous 
clean  out  holes,  through  which  the  flue  dust  that  collects  in  the  stove 
while  it  is  being  heated  may  be  removed,  will  be  placed  at  points  most 
desirable  for  the  purpose. 

iSee  Modern  Methods  of  Burning  Blast  Furnace  Gas  by  A.  N.  Diehl.  Year 
Book  of  the  American  Iron  and  Steel  Institute,  1915. 


144 


BLAST  FURNACE 


r 


\ 

I 


i 


-1! 


STOVES 


145 


Stove  Linings:  Stove  linings  is  a  term  that  corresponds  to  furnace 
lining,  and  includes  all  the  brick  work  enclosed  by  the  shell.  As  in  the 
case  of  the  furnace,  an  expansion  space  of  about  two  inches  is  left  between 
the  circular  brick  wall  and  the  shell.  For  these  linings  a  strong  yet  porous 
firebrick  is  required,  because  such  brick  absorb  the  most  heat  and  also 
give  it  up  most  readily.  The  brick  need  not  be  very  refractory,  for  the 
temperature  in  the  stove  is  relatively  low  except  in  the  combustion  chamber, 
where  a  brick  possessing  fairly  high  refractory  properties  is  required.  The 
temperature  of  the  hot  blast  is  maintained  at  about  538°  C.  (1000°  F.) 
which  marks  the  lowest  temperature  to  which  the  hottest  part  of  the  stove 


Fio.  21  a.     Cross  Section  of  Blast  Furnace  Stove  Section  C  C  of  Fig.  21. 


146  BLAST  FURNACE 


can  drop.  With  modern  stoves,  from  25  to  30%  of  the  gas  produced  by 
the  blast  furnace  is  required  to  maintain  the  blast  at  the  correct  temper- 
ature. Of  the  remainder  about  one  fifth,  (12  to  20%  of  the  whole)  is  used  by 
the  blowing  engines,  so  that  a  little  more  than  half  of  the  total  gas  produced 
by  the  furnace  is  available  as  surplus  for  the  generation  of  electrical  power. 

Dust  Catcher  and  Gas  Mains:  From  the  down-comer  the  gas  from 
the  furnace  passes  directly  into  the  dust  catcher.  Its  object,  as  implied 
by  its  name,  is  to  clean  the  gas  as  much  as  possible  of  the  flue  dust  blown 
over  from  the  furnace,  with  which  dust  the  gas  is  heavily  laden.  If  this 
dust  is  not  removed,  in  part  at  least,  it  cakes  upon  the  wal  Is  of  the  combustion 
chamber  and  small  flues  of  the  stoves  and,  dropping  down,  necessitates  frequent 
cleaning.  Besides,  it  acts  as  an  insulator  on  the  brick,  preventing  the  full 
absorption  of  heat.  Similar  conditions  also  prevail  when  the  dirty  gas  is 
burned  under  boilers.  The  dust  catcher  may  be  looked  upon  as  a  great 
enlargement  of  the  flue,  or  down-comer.  Its  diameter  is  often  20  feet  or 
more.  It  is  brick  lined,  often  has  a  dome  shaped  top,  and  a  bottom  in 
the  shape  of  an  inverted  cone.  The  principles  involved  in  its  construction 
is  that  of  greatly  reduced  velocity  accompanied  by  sudden  change  in 
direction.  By  this  means  the  dust  in  the  gas  may  be  reduced  sufficiently 
to  be  used  under  boilers  and  in  stoves  with  large  flues  very  satisfactorily. 
From  the  dust  catcher  the  gas  passes  through  a  gas  main  that  divides 
into  two  branches — one  to  supply  the  stoves  and  one  to  furnish  gas  to  the 
boilers  for  generating  steam,  which  disposal  will  now  apply  to  the  older 
and  less  progressive  plants  only.  In  up-to-date  plants,  the  gas  will  be 
subject  to  additional  and  more  efficient  treatment,  after  which  it  may  be 
used  in  the  two  ways  mentioned  or  in  internal  explosion  engines.  This 
additional  cleaning  of  the  gas  is  a  necessity  where  gas  engines  are  used, 
and  it  is  also  claimed  that  gas  for  the  stoves  is  cleaned  at  a  profit,  since 
it  eliminates  the  necessity  of  frequent  cleaning  of  the  stoves  and  permits 
smaller  checker  flues,  thus  increasing  the  heating  surface  of  the  brick. 
The  matter,  while  past  the  experimental  stage,  is  not  yet  fully  developed 
at  all  plants.  As  representing  a  highly  developed  method  of  gas  cleaning, 
the  Duquesne  works  will  furnish  a  good  example. 

Arrangement  of  Furnaces  and  Cleaning  Plant  at  Duquesne:    At 

this  plant  there  are  six  furnaces  situated  in  a  row,  for  the  full  length  of  which 
extends  a  large  gas  main,  called  the  rough  gas  main.  The  gas  from  all 
these  furnaces  may  enter  this  main  after  passing  the  dust  catchers.  From 
this  main,  gas  may  be  led  to  any  part  of  the  plant  to  be  used  in  the  raw 
state,  though  it  is  primarily  intended  to  supply  the  cleaning  plant.  The 
flow  of  the  gas  through  the  main  is  controlled  by  water  valves.  A  water 
valve  is  a  vertical  cylinder  with  a  cone-shaped  bottom;  in  its  center  is  a 
vertical  diaphragm  reaching  down  over  half  way  to  the  base  of  the  valve. 
Water  can  be  admitted  into  the  valve  to  a  level  somewhat  higher  than  the 
lower  edge  of  this  diaphragm.  With  the  water  level  below  the  diaphragm 
an  outlet  is  provided  so  that  a  current  of  gas  may  be  allowed  to  flow  through; 


GAS  CLEANING  PLANT 


147 


when  water  rises  high  enough  above  the  base  of  the  diaphragm  to  resist 
the  pressure  of  the  gas  and  prevent  its  passage  under  the  diaphragm,  the 
valve  is  sealed.  By  means  of  these,  any  furnace  can  be  shut  off  from  the 
system.  The  gas  cleaning  plant  consists  of  two  divisions  called  the  Primary 
and  Secondary.  The  primary  division  receives  and  washes  all  the  gas  that 


Blast  Furnace 


Dust  Catcher—* 


Dust  Catcher 


Dustpocket 


Fia.  22.  Diagram  showing  Route  of  Gas  from  Furnace  through 

Gas  Cleaning  Plant  to  Boilers,  Stoves  and  Gas  Engines. 

Carnegie  Steel  Company,  Duquesne  Steel  Works. 

is  brought  from  the  furnace  by  the  rough  gas  mains  and  returns  the  washed 
gas  to  the  stoves  or  boiler  houses  when  desired.     The  secondary  division 


148  BLAST  FURNACE 


receives  only  such  gas  as  is  intended  for  use  in  the  gas  engines. 

Primary  Division:  The  primary  cleaning  of  the  gas  is  accomplished 
by  vertical  water  scrubbers  and  fans.  It  reduces  the  dust  content  of  the 
gas  to  .06  grain  per  cubic  foot  of  gas  under  standard  conditions.  The 
vertical  water  scrubbers  are  the  most  important  part  of  the  equipment  in 
respect  to  the  amount  of  dust  removed  from  the  gas.  There  are  nine  of 
them,  and  the  gas  connections  for  them  are  led  to  their  bases  from  the 
gas  main  through  water-and  damper- valves.  These  scrubbers  are  vertical 
steel  cylinders,  unlined,  77  feet  6  inches  high  and  12  feet  in  diameter,  and 
are  built  of  %  inch  steel  plates.  Gas  is  admitted  at  the  base.  Water  is 
admitted  so  as  to  fall  against  the  gas,  and,  as  the  currents  flow  in  opposite 
directions,  there  is  intimate  mixture  between  them.  The  water  is  applied  to 
the  gas  in  the  form  of  a  spray  and  when  falling  in  the  interior  of  the 
scrubbers  is  like  rain  in  that  it  is  in  small  drops  and  thus  presents  the 
greatest  possible  surface  to  the  gas. 

Methods  of  Scrubbing  the  Gas:  Two  methods  of  producing  and 
supplying  the  water  spray  have  been  used  at  this  plant.  The  older  method 
employed  a  horizontal  spray  pipe  located  in  the  top  of  the  tower  and  rotated 
by  a  small  electric  motor.  Water  was  supplied  to  it  from  a  pipe  inserted 
at  the  top.  The  falling  water  was  prevented  from  striking  the  shell  by 
a  vane  in  the  bottom  of  the  spray  pipe.  Just  below  the  spray  pipe  were 
12  screens  set  together  so  as  to  break  up  the  water  stream  as  it  fell,  but 
from  that  location  the  spray  fell  uninterrupted  to  the  base,  where  it  was 
drained  out  through  a  gas  seal.  In  the  improved  form,  two  series  of  seven 
pipes  each  are  inserted  one  above  the  other.  The  water  is  forced  up  through 
screens  placed  at  six  foot  intervals  and  must  then  fall  back  through  them. 
Motor-driven  cut-off  valves  shut  off  the  water  from  each  pipe  in  turn,  making 
an  area  of  low  resistance  over  the  pipe  from  which  water  has  been  cut  off. 
The  gas  rushes  to  this  region;  then  water  is  turned  on  again  and  the  gas  is 
deflected.  A  spiral  motion  results,  giving  a  larger  exposure  of  gas  area  to 
cleaning  water  than  would  ordinarily  result.  The  scrubbers  use  about 
6,000,000  gallons  of  water  per  24  hours.  The  temperatures  of  the  gas 
entering  the  scrubbers  range  from  300°  to  600°  F.,  and  the  pressure  varies 
from  8  to  16  inches  of  water.  The  water  enters  the  scrubbers  at  river 
temperature  and  at  an  average  of  57.4°  F.  with  a  maximum  of  84°  F.  and  a 
minimum  of  33°  F.  The  dust  caught  in  the  settling  basin,  which  is  built  in 
duplicate  and  extends  from  one  end  of  the  plant  to  the  other,  averages  half 
to  three-quarters  of  a  standard  50-ton  hopper  car  a  day.  The  gas  passes 
at  a  velocity  of  four  feet  per  second  up  through  the  steel  shell  into  a 
pipe  connecting  with  a  10  foot  6  inch  main.  The  gas  leaves  at  a  temperature 
varying  from  96°  F.  to  37°  F.,  or  at  an  average  of  68 °F.  The  dust  in  the 
gas  is  reduced  from  3.5  grains  per  cubic  foot  to  .22  grain  at  standard 
conditions;  the  moisture  in  the  gas  entering  the  scrubbers  is  34  grains  per 
cubic  foot  and  on  leaving  is  8.5  grains.  About  25  cubic  feet  of  gas  is 
cleaned  per  gallon  of  water  used. 


GAS  CLEANING  PLANT  149 

The  Fans :  From  the  scrubbers,  a  large  gas  main,  10  feet.  6  inches  in 
diameter  and  about  40  feet  above  the  ground,  conveys  the  gas  to  a  number 
of  fans  that  complete  the  primary  cleaning  of  the  gas.  The  connections 
to  these  fans  are  provided  with  water  valves.  The  fans  are  located  in  a 
gas  cleaning  building,  or  fan  house,  and  are  four  in  number.  Each  fan  has 
a  rated  capacity  of  84,000  cubic  feet  of  gas  per  minute  at  100°F.  The  fans 
raise  the  pressure  of  the  gas  to  about  six  inches  of  water  and  thus  give  it 
sufficient  head  to  pass  through  the  entire  system  of  stoves,  boilers  and 
engines;  the  furnace  pressure  alone  is  not  sufficient  to  supply  this  head. 
The  gas  leaves  the  fans  at  temperatures  varying  from  93°  F.  to  35°F.,  or 
an  average  of  69°  F.  By  introducing  water  at  several  points  into  the  shell 
of  each  fan,  the  fans  are  made  to  serve  as  cleaners,  and  the  dust  content  of  the 
gas  is  reduced  from  .22  grain  per  cubic  feet  to  .06  grain  per  cubic  feet. 

Water  Separator:  From  the  fans,  the  gas  passes  through  water 
separators.  These  are  made  of  two  concentric  steel  cylinders  which  stand 
in  a  vertical  position.  Tlie  outer  cylinder  is  much  larger  in  Diameter  than 
the  inner  one  and  somewhat  longer,  so  that  the  gas,  entering  at  the  top 
of  the  outer  cylinder  and  on  a  tangent,  is  given  a  downward  spiral  motion 
and  escapes  at  the  bottom  rising  through  the  inner  pipe.  In  this  way, 
the  greater  portion  of  the  water,  owing  to  its  greater  inertia,  is  deposited 
by  the  gas  current.  From  the  water  separator  the  gas  enters  the  clean 
gas  main  and  is  distributed  to  the  stoves  and  boilers  and  also  to  the 

secondary  division. 

• 

The  Secondary  Division:  This  division  furnishes  gas  for  internal 
combustion  engines,  which  require  gas  almost  as  free  from  dust  as  the  air 
itself.  It  consists  of  four  Theisens  cleaners.  This  cleaner  is  a  combina- 
tion fan  and  cleaner.  Externally  it  has  a  form  approximately  like  that  of 
a  large  steel  cylinder  and  is  mounted  horizontally.  This  outer  cylinder  is 
stationary  and  encloses  a  similarly  shaped  but  smaller  revolving  cylinder  on 
the  shell  of  which  is  riveted  twenty-four  steel  -vanes.  These  vanes  project 
12  inches  from  the  shell  of  the  inner  cylinder  and  extend  longitudinally  in  a 
slight  spiral  to  the  circumference.  At  the  receiving  end  the  vanes  project 
beyond  the  end  of  the  cylinder  to  form  a  drawing  fan  for  receiving  the  gas, 
while  at  the  delivery  end  they  terminate  in  blades,  attached  to  the  same 
cylinder,  that  act  as  a  booster  fan  for  propelling  the  gas  through  the  succeed- 
ing apparatus.  Water  is  admitted  at  low  pressure  through  six  pipes  half 
way  up  and  on  the  side  of  the  outer  shell.  This  water  is  dashed  to  a  spray 
by  the  revolving  vanes,  and,  being  propelled  in  a  direction  opposite  to  that 
of  the  gas,  is  thoroughly  mixed  with  it,  thus  wetting  the  last  small  particles 
of  dust,  which  must,  therefore,  separate  with  the  water.  This  water  is 
let  out  of  the  apparatus  through  a  water  seal  at  the  bottom.  The  gas 
flows  through  the  shell  and  out  into  a  water  separator,  thence  to  the  gas 
main  leading  to  the  gas  engines.  The  Theisens  cleaners  have  a  rated 
capacity  of  14,000  cubic  feet  of  gas  per  minute  at  standard  conditions.  The 
gas  leaves  the  Theisens  at  an  average  temperature  of  64.2°  F.,  or  a  maximum 


150  BLAST  FURNACE 


of  91°  F.  and  a  minimum  of  35°  F.  The  water  enters  at  an  average  of  57.5° 
F.  The  dust  in  a  cubic  foot  of  gas  is  reduced  from  .06  grain  to  .009  grain. 
45.44  cubic  feet  of  gas  is  cleaned  per  gallon  of  water  consumed. 

SECTION   VI. 

EQUIPMENT   FOR   HANDLING    RAW   AND    FINISHED    MATERIALS. 

The  Boiler  House,  Power  Plant,  Pumping  Station,  Blowing  Engines, 
etc.  while  constituting  a  very  vital  part  of  the  blast  furnace  equipment 
present  features  of  more  interest  to  engineers  than  to  metallurgists  and 
are  therefore,  best  omitted  from  this  discussion. * 

Dry  Blast :  About  60%  by  weight  of  all  the  materials  entering  the 
blast  furnace  is  air.  As  air  always  contains  moisture  and  since  the  decom- 
position of  water  is  an  endothermic  reaction,  the  heat  absorbed  by  the 
amount  of  water  thus  entering  the  furnace  may  be  very  great.  It  has 
been  estimated  that  during  the  month  of  July,  for  instance,  the  average 
quantity  of  water,  per  hour,  entering  a  furnace  lising  40,000  cubic  feet  of  air 
per  minute  is  approximately  224  gallons.  That  this  quantity  of  water 
may  seriously  affect  the  operation  of  the  furnace  is  now  well  recognized, 
and  installations  for  drying  the  air  have  been  made  at  a  few  plants.  With- 
out discussing  in  detail  the  apparatus  used,  the  principle  employed  is  that 
of  refrigeration.  By  cooling  the  air  to  a  low  temperature  by  drawing  it 
over  a  system  of  pipes  cooled  with  brine,  (a  solution  of  common  salt,  NaCl2, 
or  calcium  chloride,  CaCl.2,  which  has  a  less  corrosive  action  on  the  pipes), 
which  in  turn  is  cooled  with  liquified  ammonia,  the  moisture  is  condensed 
and  frozen  on  the  pipes,  leaving  the  air  practically  dry. 

Cold  and  Hot  Blast  Mains:  It  is  still  the  most  common  practice  to 
use  undried  air,  which,  compressed  by  the  blowing  engines,  is  forced 
normally  under  the  high  pressure  of  about  15  pounds  per  square  inch  through 
the  cold  blast  main  into  the  stoves,  from  which  it  issues  highly  heated;  and 
passing  successively  through  .the  hot  blast  main,  the  bustle  pipe  and  the 
tuyeres,  begins  its  work  in  the  furnace.  In  this  connection  one  or  two 
apparently  minor  details  of  construction  referring  to  temperature  regu- 
lation and  pressure  control  should  be  noted.  Leading  around  the  stoves 
from  the  cold  blast  mam  into  the  hot  blast  main  is  a  small  pipe  called 
the  by=pass.  It  provides  a  means  of  controlling  the  temperature  of  the  hot 
blast.  The  Snort  Valve,  also  located  in  the  cold  blast  main,  is  used  to 
reduce  the  pressure  of  the  blast  at  the  end  of  a  cast  while  the  tap-hole  is 
being  stopped,  or  to  release  the  pressure  in  case  of  a  hanging  furnace. 

Appliances  for  Handling  Ores,  Coke  and  Stone:  As  was  pointed 
out  in  Chapter  III,  all  ore  is  shipped  over  the  Lakes  from  May  until 
December.  Consequently  the  ore  required  to  operate  the  furnaces  during 
the  months  intervening  between  shipping  seasons  must  be  stored  until  used, 
either  at  the  docks  or  at  the  w^orks.  This  storing  of  ore  requires  a  stock 

*For  details  on  construction  of  the  blast  furnace  and  equipment,  see  Blast- 
Furnace  Construction  in  America  by  J.  E.  Johnson,  Jr.,  published  by  McGraw-Hill 
Book  Company,  New  York. 


HANDLING  RA  W  MA TERIALS  151 

yard  with  suitable  provision  for  an  ore  pile,  rapid  means  of  unloading  cars, 
and  convenient  and  economical  methods  and  appliances  for  handling  large 
quantities  of  ores.  For  unloading  the  cars,  car  dumpers  have  been 
installed,  while  for  piling  and  delivering  the  ore  to  the  bins  over  the  stock 
house,  ore  bridges  are  employed.  The  ore,  arriving  at  the  works  in  train 
load  lots,  is  switched  to  a  siding  ahead  of  the  car  dumper,  and  the  cars 
are  unloaded  one  by  one  in  rapid  succession.  A  car,  being  pulled  up  an 
incline  to  the  platform  of  the  dumper,  is  bodily  lifted  and  turned  over  so 
as  to  empty  its  contents  into  large  larry  cars,  or  into  bins,  if  small  larry 
cars  are  used.  The  dumper  then  resumes  its  former  position,  and  the  car 
is  pushed  off  the  platform  by  the  next  car  of  ore  to  an  incline,  down  which 
the  empty  car  moves  to  a  car  siding.  Larry  cars,  designed  for  the  purpose, 
carry  the  ore  to  the  ore  pile,  where  the  ore  bridge  picks  up  the  ore  and 
dumps  it  in  its  proper  place  in  the  pile.  The  details  of  this  operation  will 
vary  much,  but  the  general  scheme  is  essentially  as  stated.  Aside  from 
the  mere  storing  of  the  ore  other  aims,  while  more  or  less  incidental,  must  be 
kept  in  mind.  In  order  to  obtain  uniform  conditions  necessary  to  keep  the 
furnace  operation  under  good  control,  it  is  desirable  to  mix  the  ore  of  each 
kind  or  grade  as  much  as  possible;  again,  the  uniformity  of  the  ore  may 
be  affected  by  dumping  on  large,  sharply  peaked  piles,  because  dumping  in 
this  manner  causes  a  separation  of  the  coarse  and  the  fine  material,  which 
always  differ  widely  in  chemical  composition.  For  similar  reasons,  the 
use  of  ore  direct  from  hopper  cars  unloaded  from  the  trestle  into  the  bins 
is  undesirable.  The  ore  is  the  only  material  stored,  both  the  limestone 
and  the  coke  being  brought  in  as  required.  All  up-to-date  plants  are 
provided  with  an  ore  trestle  running  out  over  the  bins  above  the  stock 
house.  The  bins  are  used  for  storing  smaller  amounts  of  ore,  fuel  and  flux, 
which  are  then  conveniently  available  for  immediate  use.  The  bins  are 
large  hoppers,  the  bottom  openings  of  which  are  closed  in  such  a  way  as 
to  permit  the  withdrawal  of  fixed  quantities  of  materials  as  desired.  The 
bins  for  the  three  materials  are  alike  except  that  those  used  for  coke  are 
provided  with  screens  for  removal  of  the  "fines."  In  the  most  modern 
plants  the  open  tops  of  the  bins  are  covered  with  a  heavy  grid-iron  grating, 
which  serves  the  two-fold  purpose  of  preventing  accidents,  resulting  from 
workmen  falling  into  the  bins,  and  the  stoppage  of  the  chutes  below,  due  to 
oversize  pieces  of  material  that  might  otherwise  be  dropped  in. 

Stock  House  Equipment:  Under  the  trestle  and  bins  is  a  large  space 
known  as  the  stock  house.  Here  are  found  the  mechanical  devices  which 
have  superseded  the  old  and  original  method  of  charging  by  hand.  The 
equipment  will  be  different  for  each  type  of  hoist.  If  the  skip  hoist  is  in 
use  the  arrangement  in  general  will  be  as  follows: — The  skip  tracks  will 
extend  down  beneath  the  floor  of  the  house  far  enough  to  permit  the  lowering 
of  the  skip  beneath  chutes,  which  lead  from  the  floor  so  as  to  deliver  the 
materials  into  the  mouth  of  the  skip.  These  materials  will  be  delivered 
to  the  chute  by  means  of  a  small  trolley  car,  running  on  tracks  that  extend 


152  BLAST  FURNACE 


under  the  bottom  openings  of  the  bins.  This  car— a  small  hopper  car— 
is  provided  with  a  scale  to  weigh  the  ore  and  stone  as  it  falls  into  the  hopper 
of  the  car.  In  this  way  any  mixture  of  ores  or  stone  desired  may  be 
accurately  made  up  by  weight  for  charging.  In  the  bucket  hoist  the  bucket 
itself  is  placed,  on  descending,  upon  the  weighing  car,  which  is  transported 
by  trolley  or  dinkey  from  bin  to  bin  for  the  different  ores  required  in  making 
up  the  charge.  Only  the  ore  and  stone  are  weighed,  the  coke  being  charged 
by  volume. 

Disposal  Equipment  for  the  Iron:  The  old  method  of  casting  the 
metal  in  beds  of  sand  has,  for  many  reasons,  been  replaced  by  casting 
machines.  Of  the  two  types  of  these  machines,  the  endless  chain  carrying 
a  series  of  parallel  moulds  or  troughs  with  over-lapping  edges  is  the  one 
most  commonly  used.  In  the  operation  of  this  machine,  the  molten  metal 
from  the  furnace  is  allowed  to  flow  into  ladles,  which  are  pulled  at  once 
into  the  casting  house.  Here,  the  metal  is  poured  slowly  into  a  trough 
from  which  it  flows  onto  two  lines  of  moving  moulds,  which  have  been 
previously  prepared,  to  prevent  sticking  of  the  iron,  by  being  either 
"limed"  or  "smoked."  The  chains  may  carry  the  iron  directly  through 
a  trough  of  water,  or  dump  the  half  cooled  pigs  upon  a  second  conveyor  to 
be  so  cooled.  A  number  of  modifications  of  this  machine  are  in  use. 

Equipment  for  Slag  Disposal:  The  greater  portion  of  the  slag 
produced  cannot  be  used  except  as  waste,  so  most  of  it  will  be  transported 
while  molten  to  a  convenient  spot  and  dumped.  When  the  slag  is  to  be 
used  for  certain  purposes,  as  for  making  Portland  cement,  it  is  best  granu- 
lated. This  condition  is  produced  as  the  slag  flows  from  the  furnace  by 
allowing  it  to  fall  into  a  large  concrete  lined  pit,  partly  filled  with  water 
and  known  as  the  granulating  pit.  By  forcing  a  small  stream  of  water  against 
and  from  behind  the  stream  of  molten  slag  as  it  drops  into  the  pit,  the  stream 
of  slag  is  broken  up  and  the  fineness  of  the  slag  is  increased.  Merely 
allowing  the  slag  to  fall  into  the  water  is  a  much  less  effective  method. 

SECTION   VII. 

OPERATING   THE    FURNACE. 

Blowing  In :  Upon  being  completed  and  provided  with  as  much  of  the 
equipment  described  above  as  is  necessary  or  desired,  the  active  career  of 
the  furnace  is  begun.  In  blast  furnace  parlance,  the  process  of  starting  a 
furnace  is  called  blowing  in.  It  is  carried  out  in  three  steps;  these  steps 
are  drying,  filling  and  lighting. 

Drying:  Newly  constructed  furnaces  and  stoves,  or  new  linings,  must 
be  carefully  and  thoroughly  dried  before  being  put  into  operation.  In  the 
case  of  a  furnace  fully  equipped  and  ready  to  operate,  the  drying  may  be 
accomplished  by  either  wood  fires  built  in  the  hearth  or  by  gas.  The  heat 
is  applied  very  gradually,  and  the  drying  is  continued  for  about  ten  days. 


OPERATION  OF  THE  FURNACE  153 

Filling:  After  the  furnace  is  sufficiently  dried,  it  is  allowed  to  cool 
slightly,  and  then  the  important  process  of  filling  is  begun.  While  different 
individuals  will  pursue  slightly  different  methods,  the  general  scheme  will  be 
rather  uniformly  carried  out.  Briefly  stated,  it  consists  of  first  placing  wood 
and  coke  on  the  bottom  to  a  height  somewhat  above  the  tuyeres,  about  which 
fine  kindling,  shavings,  oily  waste  or  any  material  easily  ignited  is  piled; 
then  following  the  wood  with  a  large  quantity  of  coke,  mixed  with  enough 
lime  stone  to  flux  its  ash,  and  gradually  introducing  ore  with  the  proper 
amount  of  flux.  Good  practice  requires  that  this  initial  volume  of  coke 
should  be  about  half  the  cubical  contents  of  the  furnace.  Sometimes,  to 
get  an  easily  fusible  slag  and  a  good  volume  of  it,  blast  furnace  slag  may 
be  introduced  ahead  of  the  ore.  These  are  called  the  blowing-in  burdens, 
and  additions  are  made  till  the  furnace  has  been  filled  to  the  stock  line, 
when  it  is  ready  for  lighting. 

Lighting:  Starting  the  burning  of  the  wood  in  the  bottom  of  the 
furnace  may  be  done  in  several  ways.  If  the  space  in  front  of  the  tuyeres 
has  been  filled  with  light  kindling  wood,  as  is  customary,  oil  is  poured  or 
sprayed  in  at  the  tuyeres  until  the  wood  is  thoroughly  soaked  with  it.  Then 
with  all  the  gas  burners  and  valves  in  the  gas  mains  and  the  bells  closed, 
the  bleeder  and  explosion  doors  are  opened,  a  light  blast  is  turned  on  and 
the  wood  ignited  by  inserting  hot  bars  through  the  tuyeres.  Often,  instead 
of  the  hot  bars,  a  wood  fire  is  built  in  the  stove  nearest  the  furnace,  and 
the  oil  is  ignited  by  blowing  sparks  over  with  the  blast.  With  a  light 
blast  on,  the  wood  soon  burns  away,  and  the  stock  begins  to  settle,  after 
which  the  blast  pressure  is  gradually  increased.  Some  furnacemen  start 
off,  after  the  fires  are  well  caught,  with  a  fairly  high  blast  pressure  for  a 
few  minutes,  in  order  to  drive  the  flames  well  in  toward  the  center  of  the 
furnace  and  consume  the  wood  quickly,  as  it  is  thought  that  a  better  initial 
settling  of  the  stock  is  thus  obtained.  As  soon  as  the  stock  gives  signs 
of  settling,  the  blast  pressure  is  reduced  to  that  normally  used  for  the 
remainder  of  the  blowing-in  period,  which  is  at  first  about  %  that  used 
when  the  furnace  is  in  full  blast.  Up  to  this  point  a  great  deal  of  gas  and 
smoke  escape  from  the  furnace  openings,  and  great  care  must  be  exercised, 
for  the  gases  contain  a  high  percentage  of  carbon  monoxide,  and  are  very 
poisonous.  Great  care  is  also  required  to  prevent  explosions,  because 
mixtures  of  furnace  gas  and  air  in  a  wide  range  of  proportions  are  explosive. 
Since  the  interstices  of  the  stock  in  the  furnace  and  all  the  gas  mains  are 
filled  with  air  to  start  with,  an  explosive  mixture  may  be  formed  any  time 
soon  after  the  lighting,  and  if  this  mixture  should  be  ignited  it  might 
cause  serious  damage.  The  difficulty  is  generally  overcome  by  providing 
outlets  for  the  gas  at  the  ends  of  the  gas  mains.  These  outlets  are  kept 
open  until  all  the  air  has  been  expelled,  which  condition  is  indicated  by 
the  color  and  odor  of  the  escaping  gas.  Both  men  and  fires  are  kept 
away  from  these  openings  until  it  is  time  to  use  the  gas  and  the  outlets 
are  closed. 


154  BLAST  FURNACE 


Heating  the  Bottom:  Another  feature  connected  with  the  lighting 
of  the  furnace  is  heating  up  the  bottom,  which  is  warmed  by  the  dry- 
ing-out fires  to  only  a  slight  degree  as  compared  with  the  temperature 
required  to  keep  the  slag  and  iron  that  form  in  a  molten  state.  In  order  to 
have  the  bottom  at  the  proper  temperatrue  when  slag  begins  to  form,  two 
methods  are  employed,  both  of  which  involve  leaving  an  opening  at  the 
tapping  hole  so  as  to  draw  the  flame  downward  from  the  tuyeres  upon 
the  bottom.  In  the  first  method  a  round  tapered  wood  plug,  three  or  four 
inches  in  diameter  at  the  smaller  end,  is  placed  in  the  tap-hole  and  the 
space  about  it  is  packed  full  and  tight  with  clay.  With  the  rise  in  tem- 
perature due  to  the  burning  of  the  wood  and  coke  in  the  bottom,  the  clay 
sets,  and  this  plug  is  then  removed,  which  permits  the  flame  from  within  to 
shoot  forth,  thus  heating  up  the  runner  outside  as  well  as  the  bottom  inside  of 
the  furnace.  When  slag  begins  to  flow  from  the  tap-hole,  the  opening  is 
closed  until  time  for  tapping  the  first  iron  has  arrived.  In  the  second 
method,  an  iron  pipe,  about  four  inches  in  diameter,  is  placed  in  the  fur- 
nace, before  it  is  filled,  so  that  one  ead  protrudes  from  the  tap-hole  out- 
side of  the  hearth,  while  the  other  extends  to  the  center  of  the  furnace. 
The  space  about  the  pipe  where  it  passes  through  the  wall  of  the  hearth  is 
tamped  with  clay  or  ball  stuff,  which  is  also  built  up  about  the  part  of  the 
pipe  within  the  furnace  for  a  foot  or  so  from  the  hearth  wall.  When  the 
furnace  is  lighted  the  gas  flame  is  drawn  to  the  center  of  the  bottom  to 
pour  forth  from  the  exterior  end  of  the  pipe.  This  pipe  need  not  be  moved 
until  a  fairly  large  flow  of  slag  is  attained,  when  it  is  drawn  from  the  tap- 
hole,  which  is  immediately  closed,  as  in  the  case  of  the  wooden  plug. 

The  heating  of  the  stoves  is  another  factor  connected  with  the  light- 
ing of  the  furnace.  The  temperature  of  the  hot  blast  when  the  furnace  is  in 
full  operation  is  500  to  550°  C.  (930  to  1020°  F.),  and  it  is  a  great  help  if 
the  stoves  can  be  heated  nearly  to  this  point  for  the  lighting  of  the  furnace, 
especially  as  the  furnace  and  filling  are  cold  to  the  bottom.  But  this  stove 
temperature  can  be  obtained  by  the  use  of  gas  only,  so  that  in  the  case  of 
isolated  furnaces  where  gas  is  not  available  before  starting  up  the  furnace, 
the  stoves  must  be  heated  as  hot  as  possible  for  the  lighting  by  means  of 
wood  and  coal  fires. 

Tapping:  At  the  end  of  ten  or  fifteen  hours  after  the  blast  is  on  full, 
there  will  be  a  sufficient  accumulation  of  slag  to  tap.  This  is  done  by  re- 
moving the  bott  from  the  monkey,  and  pricking  through  the  solid  slag  clos- 
ing the  opening,  if  the  cinder  does  not  flow  immediately.  The  bleeder  is 
closed  after  the  first  cinder  is  tapped,  as  the  gas  can  now  be  used  in  the 
stoves,  and  boilers  or  gas  engines.  It  requires  from  30  to  40  hours  before  much 
iron  accumulates.  When  the  iron  is  ready  to  tap,  a  hole  is  bored  by  means 
of  a  long  auger  or  drill,  electrically  or  otherwise  operated,  almost  through 
the  clay  plug  of  the  tapping  hole.  During  the  boring,  the  dust  is  blown 
put  of  the  hole  by  a  jet  of  compressed  air.  The  splasher  having  been  put 
in  place,  the  opening  is  then  completed  by  driving  a  long  pointed  bar  into 
the  furnace.  When  this  bar  is  removed,  the  iron  will  usually  flow  out,  at 


OPERATION  OF  THE  FURNACE  155 

first  slowly.  As  the  flow  of  iron  progresses,  the  opening  is  enlarged  and 
the  metal  flows  out  rapidly.  The  iron  will  then  flow  out  through  the 
runners  under  the  skimmer  to  the  ladles  provided  to  receive  it.  During 
the  flow  of  the  metal,  samples  of  the  iron  for  chemical  analysis  and  fracture 
tests  are  taken  by  collecting  small  spoonfuls  from  the  main  runner.  The 
slag,  which  follows  the  iron  near  the  end  of  the  cast,  is  stopped  by  the 
skimmer,  where  it  may  be  run  off  through  a  more  elevated  runner  to  the 
slag  ladle  or  granulating  pit.  When  the  iron  has  almost  ceased  to  flow 
from  the  tapping  hole,  and  gases  are  pouring  forth,  the  blower  signals  the 
engineer  to  reduce  the  blast  and  opens  the  snort  valve  on  the  cold  gas 
main  to  relieve  the  pressure.  Then,  the  iron  and  slag  having  been  drained 
from  the  skimmer,  the  clay  gun,  hung  on  a  crane,  is  swung  into  the 
opening,  either  by  hand  or  mechanically.  This  gun  is  provided  with  a 
steam  cylinder  which  operates  a  rammer  that  forces  a  quantity  of  clay 
mixed  with  a  little  coke  dust  into  the  tap  hole.  The  clay  forms  a  plug 
that  closes  the  opening.  This  plug  of  clay  is  then  backed  up  with  more 
of  the  mixture,  which  is  fed  into  the  gun,  through  an  opening  for  the 
purpose,  in  the  form  of  moist  balls.  As  soon  as  the  hole  is  stoppered, 
the  snort  valve  is  closed  and  the  furnace  goes  on  blast  till  next  tapping 
time — four,  five  or  six  hours  afterward. 

Care  of  Runners:  After  the  tapping  hole  has  been  closed,  from  one  to 
three  minutes  being  required,  the  troughs  are  emptied,  and  preparations  for 
the  next  cast  are  begun.  The  runners  are  cleaned  carefully  of  both  metal 
and  slag,  and  their  inside  surfaces  are  carefully  brushed  with  a  thick  clay 
or  loam  slurry  which,  when  dry,  protects  the  trough,  an.d  prevents  the 
iron  from  sticking  to  the  runner. 

Sampling  the  Iron:  Sampling  pig  iron  is  a  very  important  part  of 
every  tapping.  As  the  iron  is  graced  by  chemical  analysis,  care  should 
be  taken  to  secure  a  sample  for  the  chemical  laboratory  that  will  be  repre- 
sentative of  the  whole  cast.  This  sample,  therefore,  is  generally  made 
up  of  a  number  of  equal  portions  taken  from  the  main  runner  at  the  farther 
side  of  the  skimmer  and  at  periods  corresponding  to  the  middle  of  each 
ladle  of  metal  in  the  cast.  These  samples  may  be  in  the  form  of  shot  made 
by  pouring  the  molten  metal  slowly  into  water  or  upon  a  cold  iron  plate,  or 
they  may  be  small  castings  made  by. pouring  the  metal  into  a  mould.  In 
addition  to  these  laboratory  tests,  samples  called  sand  tests  or  chill  tests, 
according  to  the  manner  of  casting  them,  are  also  taken.  In  these  tests 
the  iron  is  allowed  to  cool  in  small  moulds  about  two  inches  square  in  cross 
section  and  four  inches  long.  The  moulds  maybe  either  of  sand  as  in  "sand 
tests"  or  of  metal,  when  they  are  called  "chill  tests."  When  cold,  the 
small  casting  is  broken  with  a  hammer,  and  from  the  fracture  thus  exposed, 
if  the  test  has  been  cooled  properly,  the  blower  is  able,  generally,  to  judge 
very  closely  as  to  the  quality  of  the  iron.  Chill  tests  of  all  slags  are 
also  taken  and  carefully  inspected. 


156  BLAST  FURNACE 


Tapping  Slag:  In  about  two  hours,  the  slag  will  have  risen  near  the 
tuyeres,  and  another  flush  will  be  necessary.  If  the  iron  is  tapped  six 
times  a  day,  only  two  flushings  of  slag  are  necessary  between  tappings, 
but  if  the  tapping  is  on  a  five  hour  schedule  three  flushings  will  be 
required. 

Changing  Stoves:  The  temperature  of  a  furnace  at  the  hearth  is  a 
matter  of  great  importance,  as  this  is  one  of  the  two  main  factors  which 
control  the  quality  of  the  iron  produced.  One  of  the  means  of  regulating 
this  temperature  is  by  changing  the  slag  composition,  as  has  been  suggested. 
Another  way  by  which  quicker  results  may  be  obtained  is  by  control  of 
the  hot  blast  temperature.  This  may  be  raised  or  lowered  by  use  of  the 
by-pass,  and  can  be  kept  high  by  proper  manipulation  of  the  stoves.  As 
a  part  of  the  routine  of  blast  furnace  work,  the  tending  of  stoves  is  of  im- 
portance. They  must  be  kept  clean  and  be  changed  regularly  and  a't  not  too 
long  intervals.  Usually  but  one  stove  at  a  time  is  employed  for  heating  the 
blast,  and  the  stoves  are  changed  once  each  hour.  Thus,  each  stove  is  heating 
for  three  hours.  In  changing  stoves  the  hot  stove  must  be  put  on  the  furnace 
before  the  cold  one  is  taken  off.  To  put  a  stove  on  hot  blast,  the  gas  burner 
is  racked  back  from  the  gas  port,  and  the  blow  off  and  chimmey  valves  are 
closed.  Then  in  quick  succession  the  cold  blast  valve  and  the  hot  blast  valve 
are  opened,  when  the  blast  is  free  to  pass  through  the  stove,  which  it  does 
in  the  direction  opposite  to  that  by  which  the  stove  was  heated.  The 
cold  stove  is  nov  taken  off,  the  procedure  being  the  reverse  of  the  above. 
The  cold  air  valve  is  closed,  and  then  quickly,  the  hot  blast  valve.  To 
relieve  the  pressure  in  the  stove,  the  blow-off  valve  is  slowly  opened,  which 
permits  the  chimney  valve  to  be  opened.  The  stove  is  then  ready  for  the 
gas,  which  is  admitted  by  racking  the  burner  forward. 

Charging  the  Furnace:  The  charging  of  the  furnace  is  a  part  of  the 
routine  that  must  be  done  with  great  care  and  cannot  be  interrupted.  The 
furnace  tends  to  empty  itself  rapidly,  and  constant  vigilance  is  necessary 
to  keep  the  stack  full.  The  proportions  of  the  materials  used  is  a  pre- 
determined quantity.  Therefore,  all  the  materials  are  carefully  weighed 
before  charging  into  the  furnace.  The  charging  is  usually  done  in  rounds. 
The  basis  of  charging  is  the  weight  of  fuel  in  each  round.  The  fuel  remains 
a  fixed  quantity,  and  any  variations  in  the  charge  are  made  with  the  ore 
and  flux.  Usually  the  coke  in  the  round  is  measured  by  volume  and 
not  weighed,  but,  of  course,  the  weight  of  the  given  volume  in  a 
round  is  known.  The  weight  of  this  coke  unit  varies  at  different  plants, 
because  it  is  subject  to  no  fixed  rule,  the  opinions  of  furnacemen 
differ  as  what  it  should  be,  and  it  is  affected  by  the  size  of  the 
furnace  and  other  conditions.  The  weights  most  often  used  are  10,000, 
12,000,  and  15,000  pounds.  Under  present  conditions  the  weight  of  ore 
in  the  rounds  will  approximate  twice  and  the  limestone  half  the  weight 
of  the  coke.  The  manner  of  charging  the  materials  is  also  subject  to 
much  variation.  Often  it  will  be  found  that  all  the  coke  in  a  round 


IRREGULARITIES  157 


will  be  charged,  followed  by  the  ore  and  limestone  mixed  together.  To 
charge  in  this  manner,  each  skip  or  bucket  of  coke  is  first  dropped  upon 
the  small  bell  or  placed  over  the  gas  seal  which  is  lowered  to  allow  the 
coke  to  fall  upon  the  big  bell.  This  operation  is  repeated  until  all  the 
10,000,  12,000  or  15,000  pounds  of  coke  has  been  dropped  upon  the  big  bell, 
which  is  then  lowered,  allowing  the  coke  to  drop  into  the  furnace.  The 
ore  and  stone  are  then  charged  in  the  same  manner.  To  illustrate  the 
variation  to  be  expected  in  the  manner  of  charging,  the  simple  scheme 
outlined  above  may  be  compared  with  the  following,  which  was  once  found 
in  use  at  a  certain  plant. 

1  skip  of  ore — mixture  of  ores  A.  and  B.   Weighed.    Small  bell  lowered. 
1  skip  of  stone  and  ore — mixture  of  stone  and  ore  C.     Weighed.     Small 
bell  lowered. 

1  skip  of  coke — not  weighed.    Small  bell  lowered. 
1  skip  of  coke — small  bell  lowered. 

Big  Bell  Lowered. 

1  skip  of  stone  and  ore — mixture  of  stone  and  ore  C. — small  bell  lowered. 
1  skip  of  ore— mixture  of  ores  A.,  B.  and  C.— small  bell  lowered, 
1  skip  of  coke — small  bell  lowered. 
1  skip  of  coke — small  bell  lowered. 

Big  Bell  Lowered. 

Some  Irregularities  of  Furnace  Operation:  The  blast  furnace,  even 
in  its  highest  development,  is  by  no  means  the  even-going,  easily-regulated 
monster  the  casual  observer  may  take  it  to  be.  Although  furnace  operations 
are  under  better  control  now  than  ever  before,  the  furnacemen  still  refers 
to  his  furnace  in  the  feminine  gender,  because,  he  knows  she  is  a  fickle 
maid  capable  of  acting  in  most  unexpected  and  astonishing  ways.  There- 
fore, a  full  discussion  of  this  subject  would  lead  to  possibilities  and  prob- 
abilities almost  without  end.  However,  the  subject  lends  itself  to  at  least 
one  positive  statement.  It  is  this:  there  are  few  situations  in  life  where 
promptness  and  decision,  forethought  and  good  judgment,  skill  and  experi- 
ence are  more  needed  than  about  a  blast  furnace  in  times  of  trouble.  A 
few  of  these  troubles  are  here  enumerated. 

Slips  are  due  to  a  wedging  of  the  stock  in  the  upper  part  of  the  stack. 
They  are  thought  to  be  caused  by  carbon  deposition,  which  may,  in  some 
cases,  be  more  in  volume  than  that  of  the  ore.  This  deposition  fills  up 
the  interstices  of  the  stock,  so  that  the  gas  can  penetrate  it  only  with 
difficulty.  When  this  condition  occurs  the  stock  beneath  the  wedged 
•portion  settles  from  that  above,  the  blast  pressure  rises  and  the  wedged 
stock  finally  falls.  The  sudden  release  of  pressure  on  the  gases  produces 


158  BLAST  FURNACE 


a  result  like  that  of  an  explosion.     Slips  of  great  violence  have  been  known 
to  tear  off  the  top  and  do  very  serious  damage. 

Scaffolding  occurs  near  the  top  of  the  bosh.  This  condition  is  often 
due  to  irregularities  in  the  working  of  the  furnace,  the  following  explanation 
often  being  suggested:  If  the  zone  of  fusion  is  suddenly  lowered,  the  pasty 
mass  at  its  top  tends  to  adhere  to  the  encircling  wall,  with  the  result  that 
an  incrustation  is  formed  which  projects  toward  the  center  of  the  furnace. 
This  mass  offers  obstruction  both  to  the  gases  and  to  the  descent  of  the 
stock.  If  this  condition  is  not  soon  remedied,  the  blast  gases  will  channel, 
perhaps  on  one  side,  in  which  case  serious  damage  to  the  lining  would 
result.  Dynamite  is  sometimes  necessary  to  break  a  scaffold.  This 
condition  is  often  referred  to  as  hanging. 

Chimneying  and  Hot  Spots:  Chimneying  is  caused  by  the  improper 
distribution  of  the  charge  with  the  coarser  material  segregating  to  the 
center  of  the  furnace.  The  hot  gases  naturally  seek  the  lines  of  least 
resistance,  and  the  principal  reaction  is  up  through  this  more  open  center, 
with  a  corresponding  slower  movement  of  the  finer  and  more  compact 
material  along  the  side  walls.  With  the  coarser  materials  segregating  next 
the  side  walls,  the  more  violent  reactions  are  next  the  brick  work,  with  a 
cold  column  in  the  centre,  and  the  condition  is  sometimes  called  pillaring. 
If  the  latter  condition  becomes  localized,  the  action  of  the  stock  and  the 
hot  gases  soon  cut  away  the  walls  adjacent  to  the  area  affected,  if  the 
condition  continues  for  any  length  of  time.  Eventually,  this  may 
develop  a  hot  spot,  showing  on  the  shell.  By  the  generous  use  of 
water  sprayed  against  the  hot  spot  the  furnace  can  sometimes  be  kept  in 
operation  for  a  considerable  length  of  time  after  a  hot  spot  shows.  In 
either  case  the  colder  material  from  the  inactive  zone  causes  a  cold  hearth 
and  poor  quality  of  iron. 

Loss  of  Tuyeres  and  Chilled  Hearth  may  be  brought  about  by  burning 
out  the  coolers  due  to  failure  of  the  water  and  by  filling  during  a  slip.  Bad 
slips  always  throw  a  great  deal  of  the  molten  slag  up  into  the  tuyeres, 
blowpipes  and  tuyere  stock  where  it  immediately  solidifies,  necessitating 
a  shut  down.  The  large  amount  of  comparatively  cold  stock  that  drops 
into  the  hearth  from  a  severe  slip  may  lower  the  temperature  of  the  molten 
iron  and  slag  below  the  fusion  point,  thus  producing  a  chill  in  the  hearth. 
When  the  tuyeres  are  finally  opened  in  case  of  a  bad  chill,  and  the  furnace 
is  on  blast,  if  necessary,  before  the  tap  hole  can  be  opened,  the  iron  can 
be  tapped  through  the  cinder  notch  after  the  removal  of  the  coolers. 

Uncertainties  and  Variables  in  Furnace  Control:  Besides  the 
irregularities  just  mentioned  which  affect  and  occur  in  the  furnace  itself, 
there  are  many  others  which  may  arise  from  outside  sources,  because  to 
obtain  uniform  working  of  the  furnace  it  is  necessary  that  all  the  raw 


BANKING  159 


materials,  the  limestone,  the  coke,  the  ore,  and  the  air,  be  kept  uniform, 
a  feat  that  is  manifestly  impossible.  Again,  the  furnace  plant  may  be 
looked  upon  as  a  composite  mechanism  containing  many  vital  parts,  of  which 
the  furnace  itself  is  but  the  central  figure.  The  prolonged  failure  of  any 
one  of  these  parts,  the  boiler  plant,  the  blowing  engines,  the  pumping  station, 
the  gas  mains,  the  water  lines,  or  the  stoves,  is  sufficient  to  close  down  the 
furnace.  All  of  these  things  are  of  great  interest  to  the  furnaceman,  but 
their  discussion  cannot  be  undertaken  in  as  brief  a  discourse  as  the  present 
one  is  intended  to  be. 

Banking:  Whenever  it  becomes  necessary  to  close  down  a  furnace 
temporarily,  it  is  banked.  This  is  done  by  charging  coke  blanks,  beginning 
a  few  hours  before  banking.  The  Amount  of  the  blanks  varies  with  the  time 
the  furnace  is  to  be  off.  After  the  blanks  have  been  charged,  the  furnace 
is  drained  as  "dry"  as  possible  of  iron  and  slag,  the  connections  to  the  rest 
of  the  plant  are  closed,  the  blast  is  shut  off,  the  blow  pipes  and  the  tuyeres 
are  removed,  and  the  openings  are  bricked  up  tight.  The  bleeders,  explosion 
doors  and  then  the  bells  are  opened,  and  the  gas  is  allowed  to  pass  out  at 
the  top.  The  furnace  may  now  remain  inactive  for  several  days  or  weeks. 
In  starting  up,  the  furnace  is  filled  up  with  coke  and  a  little  ore,  the  ashes 
are  raked  out  through  the  tuyere  openings,  the  tuyere  connections  are 
made  and  the  blast  is  turned  on.  The  same  precautions  with  regard  to  gas 
must  be  observed  here  as  in  blowing  in.  A  week  or  more,  depending  upon 
the  length  of  the  banking  peroid,  may  be  required  for  the  furnace  to 
return  to  normal  condition. 

Blowing  Out:  In  blowing  cut,  charging  is  merely  stopped  and  the 
stock  is  allowed  to  settle.  Streams  of  water  are  allowed  to  flow  into  the 
try  holes  to  keep  the  top  cool  and  prevent  warping  of  the  bells.  As  soon 
as  the  stock  line  descends  near  the  tuyeres,  the  blast  is  taken  off,  the  tuyeres 
are  removed,  and  the  rest  of  the  stock  is  later  removed  with  shovels.  This 
done,  the  career  of  the  furnace  is  ended. 

SECTION   VIII. 

THE  BLAST    FURNACE   BURDEN. 

Burdening  the  Furnace:  The  amounts  of  ore  and  stone  charge 
per  ton  (or  other  fixed  quantity)  of  fuel  is  referred  to  as  the  burden,  the 
fuel  or  coke  being  constant  in  amount.  Any  increase  in  ore  and  stone  above 
the  normal  is  spoken  of  as  a  heavy  burden,  while  the  reverse  of  this  results 
in  a  light  burden.  The  regulation  of  the  proportions  of  ore,  flux  and  coke 
is  called  burdening.  It  has  two  objects;  namely,  the  most  efficient  oper- 
ation of  the  furnace  and  at  the  same  time  the  production  of  the  grade  of 
metal  desired.  The  subject  is  of  the  greatest  importance  in  the  operation 
of  a  furnace,  and  is  a  problem  that  may  be  solved  either  by  practical  exper- 
ience or  by  calculations  based  on  theoretical  considerations.  With  a 
furnace  well  started  and  on  familiar  materials,  practical  knowledge  only 


160 


BLAST  FURNACE 


may  be  required  to  operate  successfully.  But  in  dealing  with  unknown 
materials,  theoretical  burdening  based  on  chemical  analysis  must  be  resorted 
to.  A  full  discussion  of  these  matters  would  make  this  Chapter  too 
technical  for  the  purpose  it  is  intended.  However,  as  illustrating  the  pro- 
blems that  confronts  the  blast  furnace  operator,  the  following  will  supply 
concrete  examples: 

Given:    A  furnace  with  a  certain  capacity  and  raw  materials  of  the  com- 
position shown  in  the  following  table: 
Required:    1.    To  produce  1  ton  (2240  Ibs.)  pig  iron     with    2000   pounds 

coke  or  less. 

2.    To  produce  metal   containing  silicon,    less    than    1.25%; 
sulphur,  less  than  .040%;  manganese,   as  high  as  possible; 
carbon  and  phosphorus,  not  specified. 
To  determine:    1.     In  what  proportions  the  ores  shall  be  mixed. 

2.  Weight  of  ore  mixture  in  the  charge. 

3.  Weight  of  flux  in  the  charge. 

Table  27.*    Analysis  of  Raw  Materials  Used  in  the  Blast  Furnace. 


ELEMENTS  AND  RADICALS 
Dry  Basis 

js 
£ 

ORES 

Limestone 

Coke 

1 

2 

3 

4 

% 

% 

% 

% 

% 

% 

Silica  

SiO2 
Fe 
Mn 
P 
A1203 
CaO 
MgO 
C 
C02 
S 

SOs 

Na2O- 
K2O 
TiO2 

H2O 

6.48 
56.80 
1.14 
.082 
3.22 
.11 
.14 

9.04 

54.84 
1.09 
.096 
2.70 

.18 
.26 

12.78 
52.93 
.83 
.083 
3.34 
.25 
.21 

5.86 
55.59 
.16 
.618 
3.63 
1.22 
.87 

3.43 
.30 
.08 
.006 
.86 
51.45 
1.66 

4.40 
1.35 
.07 
.030 
2.80 
.25 
.15 
90.00 

.940 

Un- 
deter- 
mined 
Trace 

Trace 
1.50 

Iron  

Manganese  

Phosphorus  

Alumina 

Lime 

Magnesia  

Fixed  Carbon  

Carbon  Dioxide  

41.43 

Sulphur  

Sulphuric  Anhydride  
Alkalies 

.03 
Trace 
.018 
14.06 

.04 
Trace 
.009 
14.50 

.04 
Trace 
.012 
15.00 

.06 
Trace 
.019 
12.10 

.060 
Trace 
Trace 
.50 

Titania.  .  .    . 

Water,  (Wet  Basis)  

*N.  B.  The  preceding  table  is  intended  to  give  a  complete  list  of  the 
elements  and  radicals  which  make  up  the  solid  materials  entering  the 
furnace,  or  the  charge.  The  gases,  i.  e.,  the  blast,  may  be  looked  upon 
as  a  mixture  of  oxygen  and  inert  gases  composed  mainly  of  nitrogen.  In  this 
mixture  the  oxygen  content  is  20.8%  by  volume  or  23.2%  by  weight. 


BURDEN  161 


Outline  of  a  Method  for  Solving  a  Burdening  Problem :  In  a  general 
way  the  solution  of  the  problem  is  arrived  at  in  the  following  manner: 
From  the  physical  condition  of  the  various  ores  and  the  amount  of  each 
on  hand,  their  relative  cost  or  other  considerations,  the  furnaceman 
first  decides  the  approximate  proportions  in  which  it  is  desirable  to  use 
the  ores.  From  these  proportions  he  is  able  to  determine  the  average 
composition  of  the  ore  mixture  in  each  charge,  the  size  of  which  he  has 
also  decided  upon.  From  this  average  he  is  able  to  calculate  the  amount 
of  ore  required  to  produce  one  ton  of  pig  iron,  and  the  weight  of  the  impuri- 
ties therein.  Then,  since  he  must  make  one  ton  of  iron  with  one  net  ton  of 
coke,  or  less,  he  is  able  to  arrive  at  the  total  impurities  in  the  ore  and  coke 
required  to  produce  one  ton  of  iron.  These  impurities,  he  separates  into 
acids  and  bases,  and  then  combines  them  according  to  the  slag  ratio  of 
acid  to  base  which  experience  has  taught  is  the  best  to  produce  the  kind 
of  iron  desired.  This  process  gives  the  excess  acids  which  must  be  fluxed 
with  limestone.  From  the  analysis  of  the  stone  he  determines  the  available 
base,  from  which  the  amount  of  limestone  required  to  flux  the  excess  acids 
in  accordance  with  the  accepted  ratio  can  be  found.  The  next  thing  to 
consider  is  the  slag  volume,  or  the  amount  of  slag  to  be  made  per  ton  of 
iron,  which  experience  has  taught  must  be  within  certain  limits  to  be  con- 
sistent with  good  furnace  practice.  If  the  volume  of  slag  is  very  low,  its 
ability  to  remove  sulphur  from  the  iron  may  be  seriously  interfered  with, 
while  if  it  is  very  high,  the  fuel  consumption  will  increase  above  that  desir- 
able, because  coke  must  be  consumed  to  furnish  the  heat  necessary  to  form 
and  fuse  the  slag.  If  the  slag  volume  falls  outside  the  limits  which  the 
furnaceman's  judgment  from  experience  has  set  for  it,  he  must  begin  all 
over  again,  starting  with  a  different  mixture  of  ores,  or  different  limestone 
or  coke.  Evidently,  with  new  materials  the  solution  of  the  problem  involves 
a  great  deal  of  try-work  with  different  combinations  of  the  materials  that 
may  be  available. 

The  Burden  Sheet:  During  the  operation  of  a  furnace,  the  burden  may 
be  changed  from  time  to  time  to  meet  the  ever  changing  conditions.  These 
changes  are  governed  by  observation  and  by  the  analysis  of  the  pig  iron  and 
slag  produced.  An  accurate  record  is  kept  of  all  changes  made,  and  of  the 
weights  and  analyses  of  all  materials  charged,  and  for  purposes  of  record  and 
of  comparison  between  the  theoretical  and  actual  conditions,  this  data  is  all 
assembled  at  certain  times,  usually  once  each  week,  placed  on  a  burden  sheet, 
and  the  theoretical  amounts  of  the  various  ingredients  of  the  raw  materials 
and  the  products  are  calculated.  To  illustrate  the  calculations  involved,  the 
following  burden  sheet  is  appended.  The  figures  given  are  based  on  a  single 
charge  instead  of  on  amounts  of  materials  used  for  any  given  length  of  time, 
otherwise  they  represent  actual  conditions  and  show  a  typical  charge  for  a 
furnace  making  basic  iron.  In  studying  the  sheet  it  should  be  kept  in  mind 
that  only  the  weights  of  the  ores,  cinder,  scale,  scrap,  coke  and  stone,  together 
with  their  analyses,  and  the  theoretical  analyses  of  the  pig  iron  are  given  to 


162 


FURNACE 


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16  cow 


o  oo  <N?o 
rn  q  qo 


3  o>o 


O  O 

<N  IN 

oo  oo 

O>  OJ 

<N  <N 


5  *     A 


1C    ^  °?   ^ 

10  -     <"~8 


1=1 

1  = 
s  . 


O 


»>    0 

aaj1 


CO  CO  CO  O 
iOO30<N 

o^  co  i>  o 


0  1 
o^  1 


O  CO  CO  CO 
COCNCN<N 


00  CN  CO  IN 

lo'oodco 


O  O  J^CO 

co  01  q»c 


o  ^  >o  >c   • 

1C    CN    rH05      • 

o  oo  *o-*    • 


CO    CO    rH  1C 
rH    (N    COrH 


>c  co  t>  t> 

O   O  CN  O 
C$  <N  00  CN 


t»O 


OOt>.(NlOO        rH 


co  co  <N 

O5  CO  CO 


1  I. 

oo     i 


ooco 


'^-fo 


FH  .00 

no 

rH    O 


ic  co    •   • 

«  «   :  : 


00  CO  COCO 
t^iCC5(N 

05  CO  000 


oooo 


o  o  oo 

iO   O  CO 


S 

° 


'iC  CO  1C  CO 

.•  (N  O  rH  O 


Socoooo 
OOrHO5 


r-((NO5OOO 
Tt<  Tt*  i—  1  (N  t> 

CO  CO  00  OOO 


TAL 
CHARGE 


TO 
CH 

ed 

lag 


Reduce 
Slagged 


CHEMISTRY  163 


begin  with,  and  that  all  the  other  figures  are  supplied  by  calculation.  Also, 
it  will  be  observed  that  the  analyses  of  the  raw  materials  are  based  on  these 
materials  in  their  undried,  or  natural,  state. 

SECTION    IX. 

CHEMISTRY  OF   THE   PROCESS 

Methods  of  Investigating  the  Reactions  of  the  Blast  Furnace:    A 

question,  which  the  non-technical  reader  is  usually  much  interested  in,  is 
this:  What  changes  do  these  numerous  ingredients  of  the  raw  materials 
undergo  during  their  passage  through  the  furnace?  Now,  the  reactions  as 
they  take  place  in  the  furnace  are  beyond  the  reach  of  thorough  investi- 
gation; but  from  a  study  of  the  chemical  properties  of  these  elements 
and  compounds  under  conditions  similar  to  those  existing  in  the  furnace 
and  from  the  chemical  composition  of  the  products,  which  is  easily  obtained 
by  analysis,  together  with  observations  made  in  working  with  the  furnace, 
reliable  conclusions  as  to  the  reactions  that  must  bring  about  the  various 
transitions  may  be  formed.  Nearly  all  the  data  necessary  to  this  study 
has  already  been  supplied.  However,  the  following  brief  review  of  the 
chemical  properties  of  the  elements  under  furnace  conditions  may  profitably 
be  made.  These  properties  are  revealed  by  laboratory  experiments  properly 
conducted  under  conditions  approximating  those  of  the  blast  furnace. 

The  Functions  of  Oxygen  and  Carbon :  20.8%  of  the  blast  by  volume 
is  oxygen,  which  enters  the  furnace  at  a  high  temperature,  about  530°  C., 
and,  coming  in  contact  with  hot  coke,  immediately  reacts  with  carbon 
giving  off  heat  thus: 

(1)  C+O2=CO2     (+97200  cal.)      l^ 

In  the  presence  of  an  excess  of  carbon  at  a  high  temjjferature,  CO2  is  at  once 
reduced  to  CO,  and  68040  cal.  are  absorbed  (2)  CO2+C=2  CO  (—68040  cal.) 
The  net  heat,  then,  from  (1)  and  (2)  is 29160  cal.  (+97200— 68040=29160  cal.) 
At  moderately  high  temperatures  the  CO  gas  formed  acts  as  a  powerful 
reducing  agent  and  will  liberate  heat  at  the  same  time,  thus: 
(3)  3CO+Fe2O3=2  Fe+3CO2  (+8520  cal.) 
—87480  cal.— 195600  cal.  +291600  cal.=8520  cal. 

At  temperatures  ranging  from  250°  C.  to  700°  C.,  a  dull  red  heat,  the  reduc- 
tion of  Fe2O3  by  CO  may  take  place  in  three  steps,  the  Fe2O3  being  successive- 
ly reduced  to  FesO^  FeO  and  finally  to  Fe.  That  the  reduction  of  the  ore 
in  the  blast  furnace  does  take  place  in  this  way  is  shown  by  the  fact  that  a 
large  part  (60%  to  75%)  of  the  flue  dust,  ejected  from  the  top  of  the  furnace, 
is  magnetic,  though  only  Fe2Os,  may  have  been  charged.  The  total  heat 
liberated  by  these  three  reactions  would  be  a  little  more  than  twice  and  the 
total  iron  reduced  one-half  as  much  as  that  in  reaction  (3)  for  equal  weights  of 
CO.  A  very  interesting  reaction  that  takes  place  between  Fe2Os  and  CO  at 
low  temperature  is  (4),  in  which  carbon  is  deposited  and  heat  is  liberated  thus: 
\  (4)  2  Fe2O3+  8  CO  =  7  CO2+4  Fe+C  (+55920  cal.) 
—391200  cal.— 233280  cal. +680400  cal. 


164  BLAST  FURNACE 


Carbon  is  not  deposited  with  magnetite  and  CO  reacting  together,  but 
it  may  be  deposited  at  temperatures  below  600  °C  by  the  action  of 
metallic  iron  upon  CO,  thus;  Fe+CO=FeO+C.  The  CO2  formed  in  the 
preceding  reactions  and  from  the  decomposition  of  limestone  may  act  as 
an  oxidizing  agent,  absorbing  or  giving  off  heat,  as  shown  in  reactions 

(5)  (6)  (7). 

/v'  (5)     Fe     +     C02    =        FeO  +       CO       (— 2340  cal.) 

— 97200  cal.     +     65700  cal.      +     29160  cal. 

(6)  3FeO         +        C  O2        =       Fe3  O4       +     C  O          (+5660  cal.) 
—197100  cal.    —    97200  cal.     +     270800  cal.     +     29160  cal. 

(7)  3Fe     +    4CO2         =        Fe3O4        +        4CO  (—1360  cal.) 

—388800  cal.     +     270800cal.     +      116640cal. 

These  reactions  will  take  place  at  temperatures  ranging  from  about  350°  C. 
to  800°  C.,  and  their  extent  will  be  governed  by  the  relative  amounts  of 
CO2  and  CO  in  the  furnace  gas,  obeying,  in  this  respect,  the  law  of  mass 
action.  To  be  reducing  the  volume  of  CO  in  the  gas  mixture  must  equal 
or  exceed  twice  the  volume  of  the  CO2. 

Carbon  alone  is  also  a  reducing  agent  toward  oxides  of  iron  at 
low  temperatures  (450°  C.  to  700°  C.),  but  the  reduction  of  ore  by  carbon 
alone  absorbs  much  heat  as  shown  by  the  following  reactions: 

(8)  3Fe2O3+C    =      2Fe3O4        -f          CO  (—16040  cal.) 
—586800  cal.    +     541600  cal.     +     29160  cal. 

(9)  Fe3O4          +      C=3FeO     +          CO  (—44540  cal.) 
—270800  cal.     +     197100  cal.     -f-     29160  cal. 

(10)  FeO  +        C=Fe         +          CO  (— 36o40  cal.) 
—65700  cal.                                    +     29160  cal. 

Under  proper  conditions  the  reduction  of  Fe2O3  by  solid  carbon  may  take 
place  in  a  direct  way,  thus: 

Fe2O3     +J?C=2  Fe+3CO  (—108120  cal.) 
—195600  cal.  +87480  cal. 

At  very  high  temperatures — say  around  1500°C. — carbon  in  large  excess 
may  reduce  manganese,  silicon  and  phosphorus  oxides,  the  reactions  being 
represented  thus: 

(11)  Mn3O4+C=3  MnO+CO— Heat  is  absorbed. 

(12)  MnO+C=Mn+CO— Heat  is  absorbed. 

(13)  SiO2+2C=Si+2  CO.— Heat  is  absorbed. 

(14)  P2  O5+5C=2P+5CO— Heat  is  absorbed. 

Some  oxygen  also  enters  the  furnace  as  water  vapor  in  the  blast,  where  the 

following  endothermic  reaction  occurs:    H2O+C=CO+H2. 

The  hydrogen  formed  may  do  work  temporarily  by  reacting  with  iron 

oxide  and  reducing  it  thus:— (15)  FeO+H2=H2O+Fe. 

But  the  water  BO  formed  is  again  decomposed  as  shown  by  the  presence 

of  hydrogen  in  blast  furnace  gas.     Therefore,  the  net   energy  result  from 

water  vapor  is  a  loss. 

In  this  connection  it  should  be  noticed  that,  since  carbon  is  the  only 


CHEMISTRY  165 


fuel  employed,  the  carbon-oxygen  reactions  must  be  relied  upon  to  furnish 
the  heat  required  in  the  process,  and  that  only  a  few  of  these  are  heat  pro- 
ducing. Reactions  (l)to  (4)  produce  most  of  the  heat  absorbed  by  other  modes 
of  reduction,  also  that  required  to  dry  the  raw  materials,  to  decompose  the 
limestone,  to  flux  the  impurities,  to  melt  the  iron  and  slag,  and  to  replace 
the  waste.  On  this  account  they  are  among  the  most  important  reactions 
occurring  in  the  furnace. 

Behavior  of  Nitrogen  in  the  Furnace:  Nitrogen  and  the  other  inert 
gases  of  the  air,  totalling  79.2%  of  the  blast  by  volume,  pass  through  the 
furnace,  for  the  most  part,  unchanged  chemically.  Since  they  equal  in 
weight  about  six-tenths  of  all  the  other  materials  entering  the  furnace, 
they  play  an  important  part  in  heat  conduction,  and  make  a  source  of 
unavoidable  heat  waste.  Some  nitrogen,  however,  may  react  with  alkali 
carbonates  and  carbon  to  form  salts  of  hydro-cyanic  acid. 
(16)  K  2CO3+4  C+N2=2K  CN+3  CO. 

This  reaction  explains  the  small  amount  of  cyanogen,  CN,  always 
present  in  blast  furnace  gases. 

Action  of  Phosphorus  in  the  Furnace:  Phosphorus  enters  the 
furnace  with  the  charge  in  the  form  of  phosphates.  At  very  high  tem- 
peratures and  in  the  presence  of  coke  (carbon)  these  compounds  are  com- 
pletely reduced,  as  shown  in  reaction  (14).  Phosphorus  reacts  with  iron 
to  form  Fe3P,  thus:  (17)  3Fe+P=Fe3P. 

This  phosphide,  being  soluble  in  iron,  becomes  a  part  of  the  metallic 
bath  in  the  blast  furnace.  Hence,  the  phosphorus  in  the  pig  iron  can  be 
controlled  only  through  the  selection  of  materials. 

Disposition  of  Sulphur  in  the  Furnace:  Sulphur  is  carried  into  the 
furnace  mainly  by  the  coke,  though  small  amounts  are  found  in  both  the 
ore  and  the  limestone.  The  greater  portion  contained  in  the  coke  enters 
in  the  form  of  FeS,  which,  when  melted,  alloys  with  the  iron  in  the  furnace; 
a  smaller  portion,  in  the  form  of  sulphates,  as  CaSO4,  enters  as  an  impurity 
in  the  ore,  limestone  and  coke,  and  is  reduced  to  sulphide  at  a  low  red  heat 
and  in  the  presence  of  carbon.  At  a  very  high  temperature  and  in  the 
presence  of  a  very  basic  slag,  or  CaO,  and  carbon,  the  following  reaction 
may  take  place^Q  (18)  FeS+CaO+C=CaS+Fe+CO.  Owing  to  lack  of 
proper  conditions  in  the  blast  furnace,  this  reaction  is  never  complete,  so 
a  small  portion  of  the  sulphur  remains  in  combination  with  the  iron.  This 
iron  sulphide,  being  soluble  in  iron,  becomes  a  part  of  the  metal. 

Behavior  of  Silicon:  Silicon  enters  the  furnace  as  SiO2,  some  of 
which  may  be  combined  with  bases  as  silicates.  At  temperatures  of  about 
1200°  C.,  corresponding  to  the  fusion  zone  in  the  blast  furnace,  the  greater 
portion  of  this  silica  combines  with  lime,  CaO,  and  other  bases  to  form 
silicates,  which  have  already  been  discussed  under  the  heading  of  slags. 
However,  at  a  high  temperature,  such  as  exists  in  the  hearth  of  the  furnace, 
and  in  the  presence  of  carbon,  silica  is  reduced,  and  the  resultant  silicon 


166  BLAST  FURNACE 


combines  with  the  iron.     (19)  SiO2+2C=Si+2CO. 

(19A)  Fe+Si=FeSi. 

Action  of  Calcium  and  Magnesium:  Calcium  and  Magnesium  enter 
the  furnace  mostly  as  carbonates.  Small  portions  may  be  in  the  form  of 
silicates,  in  which  CaO  and  MgO  are  combined  with  SiO2,  and  may  undergo 
no  chemical  change  in  the  furnace.  The  carbonates,  however,  are  decom- 
posed at  temperatures  above  800°  C.,  liberating  CC>2. 
!J  (20)  CaCO3=-CaO+CO2.  (21)  MgCO3=MgO+CO2. 

At  the  proper  temperature  for  their  formation  the  caustic  lime  and  magnesia 
in  intimate  contact  with  Si(>2  will  both  combine  with  it  to  form  slags. 

Action  of  Aluminum:  Aluminum,  in  the  form  of  alumina,  A^Oa,  and 
alumina  silicates,  is  found  in  ore,  flux  and  fuel.  Neither  alumina  nor  its 
silicates  are  reduced  under  the  conditions  that  prevail  in  a  blast  furnace. 
Al2O3,  as  already  pointed  out,  may  exert  a  marked  influence  upon  the 
fluidity  and  fusibility  of  the  slag. 

Action  of  Less  Abundant  Elements:  Titanium,  potassium,  sodium, 
zinc,  arsenic,  copper  and  chromium,  are  elements,  a  few  of  which  are  present 
in  very  small  amounts  in  the  materials  used  in  the  Pittsburgh  district. 
Titanium  enters  the  furnace  as  titania,  TiC>2,  combined  with  some  base. 
Titania  is  similar  to  silica,  SiC>2,  except  that  it  is  more  difficult  to  reduce 
at  temperatures  attainable  in  the  blast  furnace,  and  all  but  traces  of  it, 
which  is  found  in  the  iron,  passes  out  with  the  the  slag.  Under  the  con- 
ditions prevailing  in  the  furnace,  titanium  exhibits  a  slight  tendency  to 
combine  with  carbon  and  nitrogen  to  form  titanium  cyano-nitride.  This 
substance  is  sometimes  found  in  the  salamander  on  the  hearths  of  furnaces 
being  repaired.  Here,  it  occurs  in  the  form  of  small  cubes  that  have  the 
appearance  of  copper.  The  alkalies,  soda  and  potash,  are  found  in  nearly 
all  blast  furnace  slags,  and  when  they  are  present  in  the  raw  materials 
to  a  considerable  extent,  they  are  partly  volatilized  and  driven  over 
out  of  the  furnace  with  the  flue  gases,  from  which  they  may  be  separated 
with  an  installation  of  suitable  apparatus.  Zinc  is  a  very  troublesome 
element  when  present  in  blast  furnace  material.  Its  compounds  may 
be  reduced  in  the  lower  regions  of  the  stack;  but,  if  so,  the  zinc  is  vol- 
atilized, driven  upward  by  the  blast,  and  oxidized  to  zinc  oxide,  which 
condenses  on  the  walls  of  the  colder  part  of  the  flues  and  in  time  closes 
up  the  passages  to  such  an  extent  as  to  seriously  restrict  the  flow  of  the 
gases.  Zinc  oxide  also  tends  to  combine  with  the  alumina  in  the  fire 
brick  lining  of  the  furnace,  causing  the  brick  to  expand  with  consequent 
evil,  or  even  disastrous,  results.  Arsenic  acts  very  much  like  phosphorus. 
All  of  its  compounds  are  reduced,  and  the  resultant  elementary  arsenic  then 
combines  with  iron  to  form  iron  arsenide  which  dissolves  in  the  metal. 
Copper  compounds  are  readily  reduced,  yielding  metallic  copper,  which 
alloys  with  the  iron.  Chromium  is  separated  from  its  oxides  only  with 
great  difficulty  in  the  blast  furnace,  an  exceedingly  high  temperature  and  a 
special  slag  being  required  for  the  reduction  of  its  oxides. 


REACTIONS  167 


The  Reactions  Within  the  Furnace:  With  these  facts  concerning  the 
properties  of  the  various  ingredients  of  the  raw  materials  in  mind,  the 
changes  that  take  place  in  the  blast  furnace  are  easily  understood.  The 
accompanying  chart  (Fig.  23)  gives  a  graphic  representation  of  these  changes, 
showing  the  relative  weights  and  volumes  of  materials,  the  reactions  and  the 
temperatures  at  which  the  changes  take  place  and  the  final  disposition  of  the 
products.  In  studying  this  chart,  however,  one  important  fact  should  be 
kept  in  mind.  It  is  this:  Owing  to  the  conditions  prevailing  within  the  fur- 
nace, very  few,  if  any,  of  the  reactions  will  be  complete,  that  is,  use  up  all 
the  material  at  hand  at  the  location  indicated.  Thus,  the  first  reaction, 
showing  the  reduction  of  the  ore  to  metallic  iron  with  the  deposition  of  carbon, 
affects  only  a  part  of  the  ore  and  gas.  This  condition,  with  but  one  exception 
holds  for  all  these  reactions.  Even  limestone,  which  will  decompose  com- 
pletely into  lime  and  carbon  dioxide  at  1000°  if  given  sufficient  time,  will  often 
reach  the  tuyeres  as  calcium  carbonate.  The  fact  that  iron  and  manganese 
oxides  are  not  completely  reduced  is  established  by  their  presence  in  the 
slag.  The  one  exception  to  this  rule  is  phosphorus.  Its  compounds,  down  to 
small  traces,  are  completely  reduced. 

The  explanation  for  these  statements  is  to  be  found  only  in  a  careful 
study  of  chemical  laws  in  connection  with  the  conditions  prevailing  in  the 
furnace.  Such  a  study  reveals  the  fact  that  the  reactions  in  the  upper  part 
of  the  stack  of  the  furnace  are  subject  to  conflicting  tendencies.  Thus, 
there  are  in  constant  contact  with  the  solid  substances  FesC>4,  FeO,  Fe,  and  C 
the  gaseous  substances  CO  and  COs.  Of  these,  FesO^  and  CO2  are  oxidizing 
agents.  FeO  and  CO  may  act  as  either  oxidizing  or  reducing  agents,  while 
C  and  Fe  are  reducing  agents.  With  these  substances  in  contact  at  any  given 
temperature  and  in  any  given  proportions  as  shown  on  the  chart  the  reversible 
reactions  would  proceed  in  a  given  direction  until  equilibrium  should  be  estab- 
lished, and  no  further  change  would  occur  until  either  the  concentration  of  one 
of  the  reacting  substances  or  the  temperature  should  change.  Then  the  re- 
actions, subject  to  the  law  for  mass  action,  would  proceed  in  a  direction  that 
would  again  establish  equilibrium.  But  the  slow  downward  movement  of  the 
stock  to  regions  of  higher  and  higher  temperatures,  the  presence  of  an  excess 
of  carbon  and  the  rapid  upward  flow  of  the  gases,  which  has  the  effect  of  giving 
a  constant  surplus  of  CO  and  of  carrying  CO2  out  of  the  field  of  action,  tend 
to  prevent  the  establishment  of  equilibrium,  and  to  force  the  reactions 
to  proceed  in  a  direction  that  will  result  in  the  final  reduction  of  the  iron 
oxides,  with  the  consequent  oxidation  of  either  the  C  or  the  CO.  These 
same  conditions,  however,  which  tend  to  reduce  the  oxides  of  iron,  prevent  the 
complete  oxidation  of  the  CO  to  CO2,  because  the  CO,  passing  so  rapidly 
over  the  stock,  does  not  have  time  to  become  wholly  oxidized,  and  the  presence 
of  the  reducing  agents,  Fe,  FeO,  and  C,  tend  to  oppose  the  formation  of  CO2. 
The  escaping  top  gases,  therefore,  always  show  a  large  content  of  CO  much 
in  excess  of  the  CO2  content.  In  modern  furnaces,  operating  according  to 
the  prevailing  practice  with  respect  to  coke  consumption,  the  relative  volumes 


168 


BLAST  FURNACE 


I50000CU.FT  ia72ILBS.  =      2357LBS. 


GASES 

2OOLBS.    - 
DUST 


26  LBS. 
SiO* 


C0 

IOOLB5. 
Fc3Q4 


I 

2977  LBS. 
CO 

23LBS.       1.6  LB5. 
FeO  MnO 


1076 

STONE 

I  DISTANCE  FROM  f 

|  BOTTOM  IN  FT.  58 

85 


2162 
COKE 


4333 
ORE  MIX 


97-4 

CaCO, 


3167 


I 
732 


C 


60 


190.3       39.2     451.2     54.6 
AI,C\       MnO       SiO,      FeS 


4.7        2O.S* 


75 


70 


_65_ 


*  '        r 

g  Feg  O^tflCO  — *•  4 Fe  +C->-7COa 


fc 

<co  — ^ 


/C  *   |CfO 

Fe*04  +\CO  =^FeO+jCOe 


eo 


3FeO  »  C02  — ^Fe3p4  ».C 
Fe  +  C0£  — »  FeO'+  CO 


50 


45 


—  -l4Los.H£-»-|96  LeS.CO 
CaCQ,  —  >c 


40 


MgCOA — -( 


—  ,277Lss. 


FeO+C    — * 


30 


MnOC 


TAPPING  H 


25       CaOAlpOj  »^iQ^     — ^ 


J 

9  44  LBS  RP^  3760.6  LBS 


c'a 


Sfl08LBsCOz+766LB&C—  -  3574  LBS  CO 
2042LBS  0+766L85C—  *280SLB5  C  O 

—  >9.44  LBS  H2  ^132  23LBS.CO 
FeS+CaO  +  C  —  ^CaS  t  Ke  +  CO 

1  22^.5  LBS.  SLAG  =4O3.4LBaS»O4,l.2LDifeo,  i3iLBs.Mn  O 


5CO  +  2  Fe3P 


2240  LBS.PtG  IRON  =  21 05.6 LBS.Fe>  e7LBS.C, 


FIG.  23.  The  Making  of  a  ton  of  Pig  Iron.     A  diagram   showing    the   raw 
cbanges  that  take  place  therein. 


REACTIONS 


169 


Z3  LBS, 


675  8  LBS. 


6O6  LBS. 


.5LB.           4LB5.       3.6 LBS.    ILB.       4OLBS.         1.3 LBS. 
Ca3P2Ofl       AlaQ3         CaO      MgO          C FeS 

WEIGHTS  OF  RAW  MATERIALS. 


OF  CHIEF 


/APPROX.  TEMP. 
DEGREES  CENT 
275 


RELATIVE  WEIGHTS    OF  CHIEF   IMPURITIES. 


375 


SOME  IRON  SESQUIOXIDE  is  REDUCED  ANO  CARBON  DEPOSITED.    475 
SOME  IRON  SESQUIOXIPE   is  REDUCED  TO  MAGNETIC  OXIDE:.        550 

SOME  MAGNETIC  OXIPE    is  REDUCED  TO  FERROUS  OXIDE.         625 

SOME  FERROUS  OXIDE    is  REDUCED  TO  METALLIC  IRON. 

SOME  IHQN  MAV  BE  RFQXIDIZE.D  AND  CARBON  DEPOSITED.    7OO 

775 


CARBON  DIOXIDE  MAY  BE  REDUCED  BY  IRON 
OR   FERROUS   OXIDE. 


MUCH  OF  THE  CARBON  DIOXIDE    is  REDUCED  BY  CARBON. 


875 


COMBINED  WATER  REMAINING  is  DECOMPOSED. 


975 


LIMESTONE   is  DECOMPOSED. 

TOTAL  LIME  FROM  ORE  AND  STONE    =  576.4  LBS. 

CARBON    is  ABSORBED  BY  SPQNGV  IRON. 


1075 


REDUCTION  OF  IRON  OXIDES  is  COMPLETED 


1175 


PART  OF  THE  MAMGANOUS OXIDE  is  REDUCED. 


1250 


LIME.  ALUMINA,  AND  SILICA  UNITE  To  FOR.M   SLAG. 


1350 


FUSION  ZONE  FOR  ALL  SUBSTANCES  BUT  COKE 


1550 


COMBUSTION  ZONE,  (OXYGEN  AHDV/ATEK  OF  THE  AIR 
COMBINE  'WITH  CARBON  OFTHE.COKE  TO  FORM  HYDROGEN 
AND  CARBON   MONOXIDE.) 


1700 


£000 


NEARLY  ALL  THE  IRON  SULPHIDE  is  CONVERTED  INTO  CALCIUM  SULPHIDE. 

I90i3  LBS.  AliO3,  539.4LB3.  C&Q,  ZZZLes-MgO,  474  Las.Ca  S 


CIUM  PHOSPHATE  is  REDUCED  TO  IRON  PHOSPHIDE. 
SOME  SILICA  is  REDUCEI?  FORMING  IRON  SIHCIDE. 

.a2.4Les.5i,  2O.  E  LBS.  Mn.  4.13  LBS.  R  .67LB.S 


\wtR  NOTCH.. 


materials  and  the  products  of  the  blast  furnace;  their  relative   weights   and   the 


170  BLAST  FURNACE 


of  CO  and  CO2  are  approximately  2  to  1.  In  the  lower  part  of  the  stack, 
the  temperature  is  so  high  that  CO  2  cannot  exist  in  the  presence  of  carbon, 
and  any  oxide  reduced  in  this  region  results  in  the  gasification  of  a  proportion- 
ate amount  of  carbon.  This  direct  reduction  of  oxide  by  carbon  is  the  most 
inefficient  mode  of  reduction,  because  it  absorbs  much  heat,  as  shown  by  re- 
actions (8),  (9),  and  (10),  and  robs  the  tuyeres  of  carbon  needed  for  combus- 
tion. This  mode  of  reduction,  then,  is  one  the  furnaceman  strives  to  avoid  so 
far  as  possible. 

Tracing  the  Materials  Through  the  Furnace:  The  ore,  limestone 
and  coke,  upon  being  charged  into  the  top  of  the  furnace,  come  in  contact* 
with  an  ascending  current  of  hot  gases  (temperature  about  275°  C.).  The 
first  change  that  takes  place  is  the  physical  one  of  drying.  The  hygroscopic 
water,  being  first  driven  off  and  carried  out  of  the  furnace  by  these  gases, 
is  then  followed  by  the  water  of  crystallization.  The  stock,  with  its  inter- 
stitial spaces  filled  with  an  ascending  atmosphere  containing  the  reducing 
gas  CO,  starts  to  descend  toward  the  bottom  of  the  furnace  and  to  regions 
of  higher  and  higher  temperatures.  At  different  levels,  then,  chemical 
reactions  peculiar  to  the  temperatures  of  these  levels  will  occur.  At  first 
only  the  oxides  of  iron  and  carbon  suffer  change,  and  the  first  reaction  to 
occur  is  number  (4),  in  which  carbon  deposition  takes  place  at  a  temperature 
as  low  as  300°  C.  A  large  part  of  the  remaining  iron  oxide,  in  the  presence 
of  both  C  and  CO,  is  next  reduced  in  successive  levels  and  temperatures  as 
follows: 

fc      fpo 

3  Fe203+|^0=W2+2  Fe304,  begins  at  450°  C. 
Fe3O4+<       =<  ™  +3  FeO,  complete  at  600°  C.    . 


FeO    +co==\CO  +Fe'  begins  at  7°°°  C- 

At  about  800°C.  the  free  iron  is  subject  to  re-oxidation  by  CO2,  as  is 
also  the  compounds  FeO  and  Fe3O4  though  to  a  less  degree,  the  chief  action 
being  represented  by  reaction  (5).  At  800°  C.,  or  a  little  above,  the  decom- 
position of  limestone  takes  place,  thus  :  CaCO3=--CaO+CO2-  This  reaction 
is  complete  at  1000°  C.  At  900°  C.,  carbon  reduces  CO2  to  CO.  thus: 
C+CO2=2CO,  so  that  CO2  does  not  exist  below  the  60  foot  level.  From 
this  level  the  mixture  is  one  of  gangue,  quick  lime,  coke,  spongy  iron  and 
varying  amounts  of  unreduced  ore,  all  of  which  descend  to  the  fusion  zone 
with  very  little  change,  if  the  absorption  of  carbon  by  the  iron  and  the 
action  of  carbon  on  the  unreduced  ore  be  excepted.  At  this  level,  which 
is  located  at  the  top  of  the  bosh,  the  lime  combines  with  some  of  the  gangue 
and,  with  a  little  unreduced  iron  oxide  and  manganese  oxide,  forms  a  part  of 
the  slag.  The  slag,  such  as  is  already  formed,  and  the  iron,  both  now  in 
the  liauid  state,  trickle  down  through  the  interstices  of  the  coke  to  the 


REACTIONS  171 


hearth,  where  they  become  separated  by  gravity,  forming  these  two  layers; 
a  lower  or  metallic  layer  containing  all  reduced  substances  and  an  upper 
or  slag  layer  containing  all  unreduced  matter.  Here,  since  these  two 
layers  are  in  contact  with  each  other  and  with  carbon  of  the  coke,  which 
probably  extends  to  the  bottom  of  the  hearth,  or  at  least  to  within  a  few 
inches  of  the  bottom,  reactions  (11),  (12),  (13),  (14),  (17),  (18),  and  (19), 
known  as  hearth  reactions,  occur. 

Conditions  Affecting  the  Amount  of  Silicon  and  Sulphur  in  the 
Metal:  Reactions  13  and  18  should  receive  special  attention  here,  because 
they  affect  the  quality  of  metal  and  are  subject  somewhat  to  the  control 
of  the  furnaceman.  Number  (13),  SiO2+2C=Si+2CO,  depends  upon  two 
conditions,  namely,  temperature  and  basicity  of  slag.  High  temperatures 
favor  the  reaction,  while  basic  conditions  of  the  slag  retard  it.  Reaction 
(18),  FeS+CaO+C=CaS+Fe+CO,  is  also  subject  to  the  same  influences. 
Therefore,  the  conditions  which  tend  to  raise  the  silicon  in  the  iron  will 
lower  the  sulphur  content,  provided  the  high  temperature  is  obtained 
without  the  use  of  an  excessive  amount  of  high  sulphur  coke.  In  both 
these  cases  the  extent  of  the  reactions  is  governed  by  time.  The  longer 
the  time  the  farther  they  will  progress.  This  fact  results  in  a  difference 
in  composition  between  the  first  and  last  metal  in  the  same  cast.  Since 
the  iron  on  the  bottom  of  the  furnace  crucible  is  formed  four  or  five  hours 
before  that  on  the  top  of  the  layer  at  the  time  of  tapping,  these  reactions 
will  tend  to  advance  farther  in  the  first  than  in  the  last  iron  formed  under 
normal  conditions.  The  first  of  the  cast  will,  therefore,  usually  be  found 
to  contain  a  higher  percentage  of  silicon  and  a  lower  percentage  of  sulphur 
than  the  last.  This  first  iron  is  called  "hot  iron"  on  this  account. 


172  THE  BESSEMER  PROCESS 


CHAPTER  VII. 

THE  BESSEMER  PROCESS  OF  MANUFACTURING  STEEL. 

SECTION   I. 

THE   CLASSIFICATION  OF  FERROUS   PRODUCTS. 

Introductory:  In  beginning  this  chapter  it  is  desirable  to  decide  the 
question  as  to  what  constitutes  steel.  Owing  to  the  many  varieties  of  iron 
now  classed  as  steel,  a  concise  and  wholly  satisfactory  definition  is  well 
nigh  impossible.  Attempts  have  been  made  to  restrict  the  usage  of  the 
term,  but  without  success,  because  in  defining  any  term,  the  name  must 
be  taken  as  it  is  used.  Therefore,  since  an  adequate  definition  of  steel  is 
lacking,  a  brief  resume  of  the  commercial  products  of  iron  may  be  profitable. 
In  beginning  this  survey,  it  is  to  be  born  in  mind  that  the  basis  for  the 
preparation  of  the  various  ferrous  products  is  pig  iron  and  that  this 
substance,  a  direct  product  of  the  blast  furnace,  represents  the  crudest 
form  of  commercial  iron.  All  higher  grades  are  the  products  obtained  by 
different  methods  of  refinement  and  the  degree  to  which  this  refinement 
is  carried.  The  ferrous  products  may,  therefore,  be  placed  under  two 
classes,  namely,  pig  iron  and  refined  iron. 

Pig  Iron  and  Cast  Iron:  As  pointed  out  in  the  preceding  chapter, 
pig  iron  may  vary,  or  be  varied,  very  much  in  chemical  composition  and 
constitution.  This  variation  gives  the  different  grades  of  pig  iron  and 
determmes  the  use  to  which  the  metal  can  be  applied.  On  cooling,  the 
crude  forms  first  undergo  a  slight  expansion,  which  is  followed  by  a  slight 
contraction.  This  fact  makes  it  particularly  suitable  for  mould  casting, 
in  which  form  it  is  called  Cast  Iron.  Cast  iron  offers  a  high  resistance 
to  crushing,  but  all  forms  of  unrefined  iron  are  lacking  in  tenacity, 
elasticity  and  malleability. 

Malleable  Cast  Iron:  In  the  second  class  will  be  found  a  series  of 
products,  which  may  be  classified  according  to  the  initial  method  of  refine- 
ment. This  refinement  may  be  brought  about  in  two  ways, — namely,  one 
in  which  the  metal  remains  in  the  solid  state  throughout  the  process  and 
another  in  which  the  purification  involves  fusing  the  metal.  Malleable 
cast  iron  is  an  example  of  the  first  method.  Products  of  this  class  are 
obtained  from  crude  pig  iron  of  a  certain  composition  chemically,  which, 
upon  being  cast  into  the  desired  form,  is  subsequently  subjected  to  a  com- 
bined anneaMng  and  oxidizing  process  by  which  the  malleability  is 


WROUGHT  IRON  AND  STEEL  173 

developed.  In  carrying  out  the  process,  the  clean  casting  is  packed  in  iron 
oxide  and  subjected  to  a  temperature  of  about  700°  C.  for  three  or  more 
days,  when  it  is  allowed  to  cool  in  the  furnace  very  slowly.  By  this  treat- 
ment the  greater  portion  of  the  combined  carbon  is  converted  into  graphite 
that  takes  the  form  of  very  minute  particles  evenly  distributed  throughout 
the  casting,  and  so  does  not  have  the  weakening  effect  that  flakes  of  graphite 
have.  Some  carbon,  say  twenty  per  cent  of  that  originally  present  in  the 
iron,  is  oxidized  and  eliminated  from  the  metal.  It  is  said  that  a  slight 
reduction  in  the  sulphur  content  also  takes  place. 

Wrought  Iron:  At  present  there  are  two  classes  of  iron  products 
recognized  as  being  produced  by  the  method  of  purification  by  fusion.  To 
these  are  given  the  names  of  wrought  iron  and  steel.  Wrought  iron,  as 
indicated  in  the  study  of  the  blast  furnace,  may  be  produced  directly  from 
the  ore.  This  method,  however,  has  now  been  superseded  by  the  indirect 
process,  in  which  pig  iron  is  melted  in  a  reverberatory  furnace,  called  a 
puddling  furnace,  the  hearth  of  which  is  lined  with  iron  oxide.  This  treat- 
ment results  in  the  oxidation  and  consequent  removal,  from  the  metal,  of 
all  but  small  amounts  of  carbon,  silicon,  manganese,  phosphorus  and  sulphur. 
The  purification  brings  about  a  rise  in  the  fusion  temperature  of  the  iron 
above  that  of  the  furnace,  and  at  this  point  the  metal  is  removed  from  the 
furnace  in  the  form  of  pasty  balls  in  which  more  or  less  slag  is  incorporated. 
As  much  as  possible  of  this  slag  is  at  once  removed  by  hammering  or 
squeezing,  after  which  the  bloom  thus  produced  is  rolled  into  muck  bar. 
In  this  form  it  may  be  converted  into  steel  as  noted  below,  or  subjected 
to  further  treatment  to  produce  merchant  bar.  Wrought  iron  is  soft, 
tough  and  very  malleable.  It  welds  easily,  and  is  characterized  by  a 
fibrous  structure,  due  to  the  presence  of  the  intermingled  slag  and  the 
mechanical  treatment  it  receives.  Various  modifications  looking  to 
improvement  in  the  process  of  producing  wrought  iron  have  been  devised. 

Steel  is  the  term  applied  to  all  refined  ferrous  products  not  included 
under  the  classes  described  above.  It  is  distinguished  from  pig  iron  by 
being  malleable  at  temperatures  below  its  melting  point,  from  malleable 
iron  by  the  fact  thatit  is  initially  malleable  without  treatment  subsequent 
to  being  cast,  and  from  wrought  iron  by  the  circumstance  of  its  manufacture. 
In  the  case  of  wrought  iron,  the  metal  was  in  a  fused  state  during  a  part 
of  the  purifying  process  only,  whereas  the  purification  of  pig  iron  to  produce 
steel  takes  place  at  a  higher  temperature,  and  the  metal  remains  in  the 
molten  state  throughout  the  period  of  purification.  From  a  chemical 
analysis  it  is  practically  impossible  to  distinguish  wrought  iron  from  soft 
steel,  but  the  one,  being  obtained  in  a  state  of  complete  fusion  and  free 
from  slag,  may  exhibit  physical  properties  very  different  from  the  other, 
which  is  obtained  in  a  semi-fused  state  and  retains  small  amounts  of  the 
slag  incorporated  with  it.  Between  pig  iron  and  steel,  however,  a  marked 
difference  in  chemical  composition  as  well  as  in  physical  properties  is 


174 


BESSEMER  PROCESS 


observed.     All  three  substances  show  a  wide  variation  in  chemical  com- 
position.    The  following  table  may  be  studied  with  profit. 


Table  28.     Chemical  Relations  of  Pig  Iron,  Wrought 
Iron  and  Plain  Steel. 

PER  CENT.    OF 


Name 

Iron 

Carbon 

Manganese 

Sulphur 

Phosphorus 

Silicon 

Pig  Iron. 

91  —  94 

3.50  —  4.50 

.50—2.50 

.018  —  .100 

.030  —  1.00 

.25  —  3.50 

Plain 

Steel.  . 

98.1  —  99.5 

.07—1.30 

.30  —  1.00 

.020—  .060 

.002—  .100 

.005—  .50 

(.03  —  .10 

(.120) 

as  cast) 

Wrought 

Iron.  . 

99.0  —  99.8 

.05  —  .25 

.01—  .10 

.020  —  .100 

.050  —  .20 

.02  —  .20 

This  table  would  indicate  that  wrought  iron  is  not  the  purest  form  of 
commercial  iron,  as  is  often  asserted.  However,  in  wrought  iron  part  of 
the  manganese,  sulphur,  phosphorus  and  silicon  shown  in  the  table  above 
may  be  derived  from  the  incorporated  slag,  in  which  case  they  would  exert 
little  influence  upon  the  metal  itself. 

Methods  of  Making  Steel :  Formerly  it  was  possible  to  make  a  much 
finer  distinction  between  wrought  iron  and  steel  than  that  indicated  above. 
Prior  to  1856,  there  were  but  two  kinds  of  finished  steel;  they  were  known 
as  shear  steel  and  crucible,  or  cast,  steel.  Both  were  at  that  time  manu- 
factured from  blister  steel  made  by  the  cementation  of  wrought  iron.  Shear 
steel  was  made  by  piling  and  welding  blister  steel  bars  into  faggots,  which 
were  then  forged  or  rolled  into  strips  or  bands  suitable  for  cutlery.  Crucible 
steel  was  produced  by  melting  blister  steel  and  scrap  in  graphite  crucibles, 
casting  the  fluid  metal  into  moulds,  and  then  forging  these  small  ingots 
into  bars  of  the  required  size  and  shape.  These  products  were  distinguished 
from  wrought  iron  by  the  fact  that  they  could  be  hardened  and  tempered, 
and  this  property  was,  therefore,  made  the  basis  for  a  definition  of  steel. 
But  the  introduction  of  the  Bessemer  and  open  hearth  processes,  with 
their  numerous  grades  of  products,  many  of  which  can  also  be  hardened 
and  tempered  and  all  of  which  are  quite  different  from  wrought  iron,  neces- 
sitated a  revision  of  this  definition  for  steel,  because,  lacking  a  better 
name,  the  term  steel  was  applied  to  the  products  from  the  new  processes 
also.  Then,  still  more  recently,  the  advent  of  the  electric  furnace  added 
another  variety  to  the  ferrous  metals.  Finally,  the  cementation  process 


PRINCIPLES  175 


has  been  superseded  almost  entirely  by  the  crucible  process,  and  the  intro- 
duction of  alloying  elements  has  made  a  definition  based  on  the  purity  of 
the  metal  inapplicable.  It  appears  therefore  that  the  only  general  definition 
for  steel  that  can  be  offered  is  one  based  on  the  method  of  refinement. 
On  this  basis,  then,  steel  is  a  ferrous  metal,  derived  from  pig  iron  or 
wrought  iron,  which  has  been  subjected  to  a  refining  process  by  complete 
fusion. 

General  Principles  of  the  Methods  of  Purifying  Pig  Iron:  From  a 
commercial  standpoint,  the  fundamental  principle  by  which  the  purification 
of  pig  iron  is  effected  is  that  of  oxidation  in  all  cases,  excepting  the  electric 
furnace,  which  employs  both  oxidation  and  reduction.  For  the  purpose  of 
purifying  by  oxidation  two  substances  are  available.  These  substances  are  air 
and  iron  oxide,  the  application  of  which  requires  different  types  of  apparatus. 
The  two  chief  methods  of  purification,  then,  represent  attempts  to  meet 
these  requirements.  These  methods  are  known  as  the  pneumatic,  or 
Bessemer,  and  the  open  hearth,  or  Siemens'  processes.  In  both,  the  puri- 
fication may  be  brought  about  by  oxidation  alone,  in  which  case  they  are 
called  acid  processes,  or  by  oxidation  in  conjunction  with  strong  bases, 
such  as  lime,  when  they  are  designated  as  basic  processes.  By  the  first 
class  of  process,  only  the  elements  carbon,  silicon  and  manganese  are 
removed  from  the  iron,  while  the  second  method  also  removes  phosphorus 
and,  to  a  limited  extent,  sulphur.  The  basic  Bessemer  process  has  been 
named  after  its  inventors,  the  Thomas=Gilchrist,  and  the  basic  open 
hearth  is  generally  spoken  of  as  the  basic.  Each  of  the  five  purifying 
processes  mentioned  above,  namely,  the  acid  Bessemer,  the  basic  Bessemer, 
the  acid  open  hearth,  the  basic  open  hearth,  and  the  electric,  produces 
steel  having  certain  peculiar  properties,  and  with  the  exception  of  the 
electric  process,  each  requires  pig  iron  of  a  composition  different  from 
any  of  the  others.  Owing  to  the  composition  of  iron  ores  available  in 
this  country,  the  pig  iron  produced  is  best  adapted  for  treatment  by  the 
basic  open  hearth  or  the  acid  Bessemer  process;  hence,  these  are  the 
leading  methods  employed. 


SECTION   II. 

PRINCIPLES   AND    HISTORY    OF  THE   BESSEMER  PROCESS. 

Principles  of  the  Process:  Of  all  the  processes  for  the  purification 
of  pig  iron,  the  Bessemer  is  the  simplest.  Essentially,  it  consists  of  blow- 
ing air  under  pressure  through  a  bath  of  molten  metal  contained  in  a 
vessel  constructed  of  proper  refractory  materials,  whereby  a  portion  of 
the  iron,  all  of  the  silicon  and  manganese,  and  then  the  carbon  are  suc- 
cessively oxidized.  The  first  three  elements,  upon  combining  with  oxygen, 
go  to  form  a  slag,  while  the  carbon  is  eliminated  in  the  form  of  the  gases, 
carbon-monoxide,  CO,  and  carbon  dioxide,  CO2-  As  noted  elsewhere,  the 


176  BESSEMER  PROCESS 

oxidation  of  these  elements  are  exothermic  reactions,  from  which  the  heat 
required  to  maintain  the  metal  in  the  liquid  state  is  derived.  Since  steel 
produced  in  this  way,  without  recarburization,  contains  deleterious  oxides 
which  render  it  unfit  for  use,  it  is  necessary  to  add  deoxidizers  to  the  metal 
after  blowing.  This  fact  was  not  realized  at  first,  and  the  history  of  the 
process  serves  to  emphasize  its  importance. 

Some  Incidents  Connected  with  the  Early  History  of  the  Process: 

The  history  of  this  process  also  furnishes  an  example  of  the  way  in  which 
a  method  is  developed,  and  illustrates  the  fact  that  the  perfecting  of  a 
process  is  seldom  accomplished  by  one  mind  alone,  but  by  many  minds 
thinking  toward  one  goal.  The  method  was  almost  concurrently,  but 
independently,  originated  by  two  men:  one,  an  American  named  Wm.  Kelly 
of  Eddyville/  Ky.;the  other,  an  Englishman,  the  illustrious  inventor,  Henry 
Bessemer.  Although  Kelly  did  not  apply  for  patents  until  1857,  almost 
two  years  after  Bessemer's  English  patent  was  granted,  his  application 
was  allowed  on  grounds  of  priority,  because  he  was  able  to  prove  that  he 
had  worked  out  the  idea  as  early  as  1847.  In  the  same  year  that  he  made 
application  for  patents,  Kelly  erected  a  tilting  converter  for  the  Cambria 
Steel  Works  at  Johnstown,  Pa.  This  vessel  is  still  preserved.  Lacking 
financial  means,  however,  Kelly  was  unable  to  perfect  this  invention,  and 
after  much  litigation  with  the  Bessemer  interests,  a  settlement  was  made, 
whereby  Kelly  dropped  out  of  the  game.  Bessemer,  on  the  other  hand, 
in  addition  to  conceiving  the  idea  and  putting  it  to  trial,  continued  his 
experiments  in  the  face  of  great  difficulties  and  many  failures  until  he  had 
brought  the  process  to  a  high  degree  of  perfection.  At  first  Bessemer 
accidently  employed  only  Swedish  iron,  which  had  a  low  phosphorus  and 
a  high  manganese  content,  and  was  very  successful  in  converting  it.  Then, 
it  having  been  adopted  by  many  manufacturers,  the  process  failed  when 
applied  to  English  irons  which  were  high  in  their  phosphorus  and  low  in 
their  manganese  content,  and  prejudice  and  opposition  to  the  method 
became  so  great  among  steel  makers  that,  in  order  to  save  his  process, 
Bessemer  was  obliged  to  build  a  steel  works  himself.  His  plant,  built  at 
Sheffield,  began  to  operate  in  1860. 

Importance  of  Manganese :  At  the  Sheffield  works  the  process  was  used 
at  first  to  produce  high  carbon  steels  from  Swedish  pig  iron  only,  because  low 
carbon  steels,  obtained  by  subjecting  the  metal  to  a  full  blow,  were  almost 
invariably  hot  short,  even  when  made  from  the  excellent  Swedish  iron. 
This  defect  was  later  overcome  by  the  addition  of  manganese  in  the  form 
of  spiegeleisen,  the  beneficial  effects  of  which  were  first  recognized  by 
R.  Mushet  as  early  as  1856.  With  the  adoption  of  the  use  of  manganese, 
mild  or  soft  steels  produced  by  the  process  came  into  so  great  demand 
that  the  former  practice  in  blowing  was  abandoned  in  England,  though  it 
is  still  employed  in  Sweden.  The  first  Bessemer  plant  in  this  country  was 
erected  in  1867. 


HISTORY  177 


Thomas  and  Gilchrist:  The  removal  of  phosphorus  by  the  use  of  a 
basic  lining  and  the  addition  of  lime  ta  the  bath  was  first  conceived  by 
Thomas,  who  made  known  the  success  of  his  scheme  in  1878.  In  the  develop- 
ment of  this  process,  Thomas  was  assisted  by  his  cousin,  the  chemist 
Gilchrist,  hence  the  name  Thomas-Gilchrist. 

Other  Improvements :  While  the  process  was  highly  developed  along 
mechanical  lines  by  Bessemer,  himself,  it  remained  for  Alexander  Holley, 
an  American  Engineer,  to  introduce  many  improvements  in  the  erection  of 
Bessemer  plants.  The  most  important  of  these  was  his  invention  of  the 
detachable  bottom,  which  will  be  described  later.  Another  important 
invention  was  that  of  the  hot  metal  mixer,  since  it  furnished  a  ready  supply 
of  molten  metal  of  fairly  uniform  composition,  thus  allowing  the  process 
to  be  operated  much  more  rapidly  and  economically.  This  vessel,  also  to 
be  described  later,  was  the  invention  of  W.  R.  Jones  of  the  Carnegie 
Steel  Company's  Edgar  Thomson  Plant  at  Braddock. 

Plan  of  Study:  Before  beginning  a  more  minute  description  of  the 
process  as  it  is  carried  on  with  these  modern  improvements,  it  is  well  to 
note  that  the  details  of  the  operation  will  vary  much  in  different  plants 
as  well  as  in  different  countries.  The  description,  therefore,  must  be  either 
very  general  in  character,  or  be  restricted  to  some  one  plant  which  will 
suffice  as  an  example  for  all.  For  the  present  purpose,  it  is  best  to  follow 
the  latter  course,  and  the  Carnegie  Steel  Company's  plant  at  the  Edgar 
Thomson  Works  is  selected  to  serve  as  such  an  example.  General  features 
of  great  importance  may  then  be  introduced  in  connection  with  the  dis- 
cussion of  the  various  topics.  At  these  works,  the  product  from  eleven 
modern  blast  furnaces  is  available  to  supply  both  the  open  hearth  plant 
of  fourteen  90-ton  furnaces  and  the  Bessemer  plant  of  four  converters,  the 
maximum  capacity  of  which  is  twenty  tons. 


SECTION   III. 

EQUIPMENT  AND   ARRANGEMENT  OF  THE   EDGAR  THOMSON   PLANT. 

The  Converter  House:  The  four  converters  are  arranged  in  a  row 
along  one  side  of  the  converter  building,  which  is  located  in  one  corner  of 
the  works  in  close  proximity  to  the  rail  mills.  The  converters,  being  of 
the  concentric  type,  tilt  in  two  directions,  in  one  direction  for  charging 
and  in  another  for  pouring.  On  the  charging  side  of  the  vessels  the  building 
is  erected  three-story  fashion.  The  ground  floor  extends  under  the 
converters  and  offers  space  for  the  removal  of  bottoms,  slag,  etc.  The 
second  floor,  designated  as  the  charging  floor,  is  on  a  level  with  the 
trunnions.  From  this  floor  all  molten  materials  are  charged  into  the 
vessels.  From  the  third  floor,  called  the  scrapping  floor,  all  cold  materials 
are  charged.  Serving  the  four  converters  on  the  pouring  side,  are  two 
jib  cranes  for  handling  the  steel  ladles  into  which  the  metal  is  poured  after 


178 


THE  BESSEMER  PLANT 


EQUIPMENT  179 


each  blow.  These  cranes  may  be  swung  around  so  as  to  deliver  the  steel 
to  stationary  teeming  tables  located  in  front  of  the  teeming  platform  which 
extends  along  the  side  of  the  building  opposite  the  converters.  Between 
this  platform  and  the  tables,  which  support  the  ladles  during  the  teeming 
process,  is  laid  a  narrow  gauge  track,  along  which  the  ingot  moulds,  set 
upon  small  cars,  are  moved  during  and  after  the  teeming.  This  motion 
in  front  of  the  platform  is  imparted  by  means  of  dogs  attached  to  three 
hydraulically  operated  cylinders  that  lie  between  the  rails  of  the  tracks. 
All  the  operations  of  the  converters  and  jib  cranes  are  controlled  from 
two  pulpits  in  opposite  corners  of  the  building  and  above  the  teeming 
platform.  Just  back  of  the  converter  building  and  inter-communicating 
with  it  through  an  open  side  beneath  the  charging  floor,  is  the  bottom 
house,  equipped  with  over-head  cranes  and  buggies  for  handling  bottoms. 
Here  the  frequent  repairs  to  bottoms  are  made.  As  these  repairs  must  be 
made  with  wet  refractories,  new  bottoms  require  thorough  drying  before 
being  put  into  service.  For  this  purpose  six  drying  ovens,  each  large 
enough  to  contain  two  bottoms,  are  provided.  Built  against  one  end  of 
the  converter  house,  like  the  wing  of  a  building,  is  a  cupola  house.  It  also 
is  inter-communicating  with  the  converter  building  on  its  charging  floor. 
In  the  angle  formed  by  the  cupola  and  bottom  houses  are  kept  the  stores 
of  cold  pig  iron,  spiegel,  and  ferro  manganese,  while  beyond  these 
will  be  found  a  building  in  which  is  housed  suitable  rock  crushing  machines 
and  Chilean  mills  for  crushing  and  mixing  the  refractory  materials  used 
in  making  up  the  various  mixtures  required  for  bottoms  and  repairs  about 
the  plant. 

The  Larger  Accessories:  The  cupolas,  blowing  engines,  mixers  and 
strippers,  are  each  separately  housed  and  are  located  at  various  distances 
from  the  converter  house.  All  these  accessories  play  a  very  vital  part  in 
the  process  and  in  the  operation  of  the  plant,  hence  are  deserving  of  special 
consideration. 

The  Cupolas:  In  former  times,  when  converter  plants  were  operated 
as  independent  units,  detached  and  far  removed  from  the  blast  furnaces, 
cupolas  were  used  to  melt  the  cold  pig  iron  preparatory  to  charging.  At 
this  plant  furnaces  are  used  only  for  melting  the  pig  iron  and  spiegel  mixtures 
employed  as  recarburizers.  In  construction  a  cupola  is  cylindrical  in  shape 
and  resembles  a  miniature  blast  furnace.  Those  at  Edgar  Thomson  Works 
are  eight  feet  in  diameter  outside  and  some  twenty  feet  in  height,  measur- 
ing from  the  mantle  to  the  charging  doors.  Like  the  blast  furnace,  there 
is  an  opening  at  the  bottom  of  the  hearth  for  tapping  out  metal  and  another 
for  slag.  Above  these  openings  are  inlets  for  ten  tuyeres,  through  which 
cold  air,  under  a  pressure  of  six  to  ten  ounces,  is  blown  by  fans.  Near 
the  top  are  the  two  large  openings  or  doors  for  charging,  directly  opposite 
each  other  and  opening  upon  the  charging  floor.  A  little  above  these 
openings,  a  contraction  of  four  or  five  feet  in  the  outside  diameter  of  the 


ISO  BESSEMER  PROCESS 


shaft  forms  the  stack,  also  about  twenty-four  feet  high,  for  the  escape 
o-f  gases.  The  entire  furnace  rests  vertically  on  a  mantle  which  is 
supported  by  a  number  of  columns  fixed  upon  a  firm  foundation.  This 
construction  permits  the  use  of  the  drop  bottom,  which  facilitates  the 
removal  of  worn-out  linings,  the  frequent  repairing  required  by  the  lower 
lining,  and  the  rapid  discharge  of  the  stock  in  case  of  emergency.  For  the 
sake  of  economy,  the  lining,  or  wall,  is  made  of  different  materials.  The 
upper  wall,  for  a  distance  of  about  four  feet  below  the  charging  doors,  is 
made  of  fire  brick  and  is  nine  inches  thick.  Below  this  brick  work,  the 
wall  is  built  of  firestone  and  is  gradually  increased  in  thickness,  forming  a 
kind  of  bosh  above  the  hearth,  the  walls  of  which  are  about  eighteen  inches 
thick.  No  attempt  is  made  to  cool  these  walls,  so  it  is  customary  to 
back  up  the  firestone  of  the  hearth-wall  with  fire  brick  in  order  to  safe- 
guard the  steel  shell.  The  shell,  like  that  of  the  blast  furnace,  supports 
and  re-enforces  the  masonry.  It  is  made  of  steel  plates,  which  are  riveted 
together. 

Charging  the  Cupola:  The  cupola  charge  is  composed  of  coke,  spiegel 
and  pig  iron,  in  alternate  layers  of  metal  and  coke,  to  the  last  of  which 
is  added  sufficient  limestone  to  flux  the  ash.  When  the  orders  call  for  steel 
with  a  high  content  of  silicon,  ferro-silicon  is  also  added  to  the  charge. 
The  ratio  of  coke  to  metal  varies  a  little.  At  all  times  the  amount  of  fuel 
will  be  as  small  as  possible,  both  for  the  sake  of  economy  and  to  exclude 
sulphur  and  phosphorus,  which  are  absorbed  by  the  metal,  as  much  as 
possible.  Sulphur  in  the  charge  does  not  result  in  a  rise  in  the  sulphur 
content  of  the  molten  spiegel,  but  in  a  waste  of  the^manganese,  which  reacts 
with  the  ferrous  sulphide  to  form  manganous  sulphide,  and  goes  off  wit/h  the 
slag.  Ordinarily,  the  coke  will  be  about  8%  and  the  stone  about  2^%  of 
the  metallic  charge. 

The  Blast:  Just  outside  the  converter  house,  on  the  pulpit  side, 
is  the  blowing  room.  Here  are  located  three  steam  blowing  engines  of  the 
compound  vertical  type,  which  create  the  air  blast  for  the  converters.  The 
bla,5t  from  'these  engines  is  delivered  into  a  common  main,  through  which 
it  is  conducted  into  the  converter  building,  where  it  is  distributed  through 
a  manifold  to  lines  leading  separately  to  the  four  vessels.  The  admission 
of  air  to  the  vessels  and  its  pressure  are  nicely  regulated  by  a  system  of 
valves  under  the  control  of  the  blower.  Thus,  the  pressure  on  the  main  is 
maintained  at  about  25  pounds  per  square  inch  by  means  of  a  blow-off  valve, 
which  is  used  to  regulate  the  pressure  while  the  vessels  are  charging  or 
pouring.  In  case  some  of  the  converters  are  not  being  operated,  one  or  more 
of  the  blowing  engines  is  stopped.  By  means  of  a  second  valve,  operated 
from  the  pulpit  by  a  screw  control,  a  pressure  of  18  to  20  pounds  per 
square  inch  is  maintained  on  the  line  leading  to  each  vessel.  Under  this 
pressure  the  blast  may  be  almost  instantaneously  admitted  to  or  shut 
off  from  the  vessel  by  means  of  a  third  valve  of  the  butter-fly  type.  A 
fourth  valve  provides  a  means  by  which  steam  may  be  admitted  to  the 


EQUIPMENT  181 


blast  line  as  required.  The  limits  of  blast  pressure  to  the  converter  are 
about  10  and  25  pounds  per  square  inch.  The  lower  pressure  is  just 
about  sufficient  to  keep  the  metal  out  of  the  tuyeres  in  a  normal  charge, 
while  if  the  higher  pressure  be  exceeded,  large  amounts  of  metal  are  blown 
out  of  the  converter. 

The  Mixers:  The  supply  of  molten  pig  iron  is  obtained  from  two 
200-ton  hot  metal  miners  located  near  the  blast  furnaces  and  some  three 
hundred  yards  from  the  converter  mill.  They  are  large  vessels  constructed 
of  steel  plates  riveted  together  to  form  a  shell,  which  is  lined  with  silica  or  a 
good  grade  of  fire  brick.  The  vessels  at  this  plant  represent  the  oldest  type. 
They  have  a  rectangular  horizontal  section  and  discharge  the  metal  by 
tilting.  This  type  has  a  slightly  arched  roof  and  a  bottom  which  slopes 
from  the  front  or  pouring  end  toward  the  rear.  The  axis  of  rotation  is 
located  at  the  bottom  near  the  center  line  of  the  vessel.  Molten  iron 
from  the  blast  furnaces  is  conveyed  to  the  mixer  in  tipping  ladles,  from 
which  the  metal  is  poured  into  the  mixer  through  an  opening  in  its  top  at 
the  rear  end.  In  the  opposite  end  another  opening,  provided  with  a  spout, 
permits  the  drawing  off  of  hot  metal  as  required  by  merely  tilting  the 
mixer,  thus  permitting  the  metal  to  be  weighed  with  a  fair  degree  of  exact- 
ness. These  mixer's  are  not  provided  with  gas  burners,  as  is  customary, 
for  very  little  heat  above  that  held  by  the  metal  is  ever  required  to  keep 
the  contents  molten. 

Importance  of  the  Mixer:  The  hot  metal  mixer  is  almost  indis- 
pensable to  a  modern  Bessemer  plant,  or  for  that  matter,  to  any  steel 
making  plant.  Primarily  the  mixer  serves  as  a  storage  place  for  the  hot 
metal  from  the  blast  furnace,  and  in  performing  this  function  bestows  great 
benefits.  Thus,  not  only  is  the  heat  from  the  hot  pig  iron  conserved,  but  the 
metal  delivered  to  the  vessel,  or  vessels,  is  of  a  more  uniform  composition 
than  could  be  otherwise  obtained.  Again,  since  the  capacity  of  the  modern 
mixer  permits  it  to  contain  casts  from  several  furnaces,  iron  low  in  some 
elements  may  be  mixed  with  some  that  is  high  in  the  same  ingredients; 
and  so  it  is  possible  to  extend  the  chemical  limits  of  the  iron  receivable. 
Mixers  have  been  constructed  of  various  shapes  and  sizes.  Their  capacities 
will  range  from  150  to  1200  tons,  but  the  tendency  in  all  modern  construction 
is  toward  the  larger  size.  Purification  of  the  metal  is  said  to  take  place 
to  a  slight  extent  in  the  mixer,  sulphur  being  the  chief  impurity  removed. 
The  reduction  in  sulphur,  however,  is  only  noticeable  when  the  manganese 
content  of  the  iron  is  high.  This  removal  is  at  all  times  so  small  as  to  be 
of  minor  importance. 

The  Stripper:  One  of  the  most  efficient  and  economical  inventions 
contributed  to  the  steel  business  is  the  stripper.  As  its  name  indicates, 
it  is  a  device  whereby  the  moulds  are  pulled,  or  stripped,  from  the  ingots 
after  the  metal  has  cooled  sufficiently  to  form  a  solid  shell  on  their  outside 
surfaces.  Those  at  the  Edgar  Thomson  Works  are  of  a  late  type  and  are 


182  BESSEMER  PROCESS 


electrically  operated.  A  stripper  of  this  type  is  in  the  form  of  a  strong 
over-head  crane,  from  which  is  suspended  a  vertical  arm,  provided,  in  place 
of  a  hand,  with  two  jaws  that  fit  over  lugs  cast  on  either  side  and  near  the 
top  of  the  mould.  Operating  between  the  jaws  is  a  ram,  or  plunger,  capable 
of  exerting  pressure  on  the  top  of  the  ingot,  while  it  is beingstripped, sufficient 
to  balance  the  pull.  In  stripping  an  ingot,  the  jaws  engage  the  lugs  and 
exert  a  powerful  pull  upward,  while  the  ram,  having  been  inserted  through 
the  top  of  the  mould,  holds  the  ingot  on  the  stool  till  the  mould  is  loosened. 
The  mould  is  then  raised  high  enough  to  clear  the  ingot  and  placed  upon 
an  empty  car  standing,  ready  to  receive  it,  on  a  track  next  and  parallel  to 
that  on  which  the  stripped  ingot  stands.  Electric  strippers,  owing  to  the 
fact  that  they  are  travelling,  possess  a  decided  advantage  over  the  older 
type  of  hydraulically  operated  machines,  which  are  stationary. 

The  Casting  Equipment  includes  the  teeming  ladles,  ingot  moulds, 
stools,  and  cars.  The  teeming  ladle,  which  acts  as  a  container  for  the 
finished  steel  while  casting,  is  a  large  cup-shaped  vessel  made  of  steel  and 
lined  with  a  few  inches  of  "ball  stuff."  As  slag  is  liable  to  spoil  the  ingots 
if  allowed  to  flow  into  the  moulds,  steel  cannot  be  poured  from  a  vessel 
by  tipping,  but  must  be  teemed  from  a  small  hole  in  the  bottom.  For 
opening  and  closing  this  hole,  the  vessel  must  be  fitted  with  a  stopper 
that  can  be  operated  from  the  teeming  platform.  This  stopper  consists  of 
a  steel  rod,  protected  with  fire-clay  sleeves,  to  the  lower  end  of  which 
is  fastened  a  stopperhead,  made  of  plumbago  bonded  with  clay,  that  fits 
neatly  into  a  nozzle  placed  in  the  bottom  of  the  ladle.  The  upper  end  of 
this  stopper  is  fastened  to  a  goose  neck  that  fits  over  a  vertical  sliding 
bar  attached  to  the  outside  of  the  ladle.  This  bar  is  provided  with  a  lever 
by  which  it  may  be  raised  or  lowered,  causing  a  like  movement  of  the 
stopper.  To  guard  against  a  leaking,  or  "running,"  stopper  the  nozzle 
may  be  filled  with  dry  sand  or  loam,  which  is  held  in  place  by  a  sliding 
plate  on  the  outside.  When  the  ladle  is  ready  to  teem,  this  sand  is  easily 
punched  out  of  the  nozzle  after  removing  the  plate. 

The  Ingot  Moulds  into  which  the  finished  metal  is  teemed  are  made 
of  cast  iron  and  may  be  of  almost  any  convenient  form  and  size  to  suit 
the  respective  blooming  mills.  At  these  works,  the  standard  moulds  are 
about  6  feet  high,  have  a  square  section  of  23%  inches  at  the  bottom,  with 
corners  slightly  rounded,  'and  taper  sufficiently  to  allow  the  mould  to  be 
stripped  readily  from  the  ingot.  The  moulds  are  open  at  both  ends,  and, 
when  ready  for  teeming,  rest,  big  end  down,  on  heavy  cast  iron  plates,  called 
stools.  The  stools  are  mounted  in  twos  on  small  cars,  or  buggies,  which  are  so 
constructed  that  their  sides  form  aprons  that  protect  both  the  track  on  which 
the  cars  run  and  their  own  running  gear  from  splattering  by  hot  metal  during 
the  teeming  of  the  metal  from  the  steel  ladle.  The  care  of  the  moulds  is 
very  important,  since  defects  here  are  very  likely  to  show  up  in  the  finished 
material  after  rolling.  Their  sides  must  be  kept  smooth  and  clean,  and 
the  teeming  must  be  done  so  as  to  avoid  splattering  their  sides,  if  possible. 


CONVERTER  CONSTRUCTION  183 

After  being  stripped,  the  moulds  are  inspected  and,  if  their  condition  is 
satisfactory,  may  be  used  again.  So,  after  cooling  to  a  point  where  the 
hand  may  be  held  against  them,  they  are  cleaned,  then  sprayed  inside  and 
around  the  tops  with  a  clay  wash  to  prevent  the  steel  from  sticking,  and 
marked  for  size  of  ingot  required.  As 'soon  as  the  clay  wash  is  dry,  the 
mould  is  ready  to  receive  the  molten  steel.  Usually  about  seventy  ingots 
may  be  cast  in  one  mould  before  it  is  scrapped. 


SECTION   IV. 

CONVERTER  CONSTRUCTION  AND    REPAIRS. 

General  Features  Pertaining  to  Converters:  As  to  the  form  and 
size  of  converters,  methods  of  admitting  the  blast,  and  removing  the  steel 
after  blowing,  there  are  several  possible  arrangements,  and  converters  have 
undergone  many  modifications.  Thus,  as  was  originally  the  plan,  the  air 
might  be  admitted  horizontally  through  the  wall  of  the  vessel  near  the 
bottom,  in  which  case  the  vessel  would  be  of  the  side=blowing  type;  or 
a  blast  of  air  will  be  forced  upward  through  openings  in  the  bottom  of  the 
vessel,  to  which  method  the  term  bottom  blown  is  applied.  To  facilitate 
the  charging  of  materials  into  the  vessels  and  the  removal  of  metal  from 
them,  converters  are  now  always  constructed  so  that  they  may  be  rotated 
on  their  shorter  axis  through  arcs  of  varying  size.  Such  converters  are  of 
the  tilting  type.  The  first  vessels  were  of  the  fixed  type,  the  metal  being 
tapped  through  a  hole  in  the  wall  at  the  bottom.  In  both  size  and  shape, 
vessels  still  vary  much.  The  capacity  will  range  from  5  to  25  tons.  The 
vessels  at  Edgar  Thomson  are  11  feet  in  diameter,  outside  and  measured 
along  their  axis  of  rotation,  and  almost  18  feet  long.  As  to  form,  converters 
were  at  first  somewhat  pot-shaped.  Attempts  to  design  vessels  that  would 
retain  heat  and  prevent  the  ejection  of  materials  has  led  to  two  general 
forms,  each  with  its  own  advantages.  In  both  forms  the  upper  diameters 
are  shortened,  forming  the  nose  of  the  vessel  and  leaving  a  small  opening 
in  the  top,  which  forms  the  mouth.  The  body  may  retain  the  form  of 
the  cylinder,  as  in  the  straight=sided  type,  or  be  narrowed  at  the  bottom 
also,  in  which  case  the  body  has  a  curved  contour  and  somewhat  resembles 
an  egg  in  shape.  The  mouth  may  be  located  at  the  top  concentric  with 
the  bottom  and  in  a  plane  parallel  to  it,  or  it  may  be  placed  to  one  side, 
in  which  case  the  opening  lies  in  a  plane  at  an  angle  to  the  bottom  and  is 
then  called  eccentric.  The  vessels  at  Edgar  Thomson  Works  are  all  of 
the  bottom  blown,  curved  body,  tilting,  concentric  type. 

Parts  of  Converter:  For  convenience  in  constructing  the  vessel  to 
allow  for  contraction  and  expansion  and  for  making  repairs  later,  these 
converters,  as  are  all  bottom  blowing  types,  are  constructed  in  three 
separate  parts,  known  as  the  nose,  the  body,  and  the  bottom.  The  shell 
for  each  of  these  parts  is  made  of  heavy  steel  plates,  all  firmly  riveted 


184  BESSEMER  PROCESS 

together.  The  nose  section  is  bolted  to  the  body,  but  the  bottom  is  held  in 
place  against  the  lower  edge  of  the  body  by  linked  key  bolts.  The  links  of 
these  key  bolts  fit  over  lugs  on  the  body,  while  the  key  bolts  themselves 
fit  between  lugs  on  the  bottom,  making  it  easy  to  key  the  two  parts 
firmly  together.  When  it  is  necessary  to  replace  an  old  bottom  with  a 
new  one,  the  keys  can  be  very  quickly  knocked  out  or  driven  in  with 
sledges  in  the  hands  of  the  workmen.  The  shell  for  the  body  is,  itself, 
made  up  of  three  parts,  known  as  the  nose  section,  the  journal  section,  and 
the  shoulder  section.  The  journal  section  is  made  up  of  a  heavy  band 
to  which  the  two  trunnions  that  support  the  vessel  are  attached.  All 
these  parts  are  firmly  bound  together  by  a  great  number  of  long  key  bolts 
attached  to  the  shoulder  and  nose  sections,  respectively.  The  trunnions 
rest  on  bearings  in  a  frame  work  which  is  supported  by  cast  iron  columns. 
On  the  end  of  one  of  the  trunnions,  both  of  which  are  hollow,  is  the 
connection,  made  through  a  packed  joint,  to  the  blast  line.  From  capped 
openings  on  this  same  trunnion  between  the  bearing  and  the  vessel,  a 
copper  goose  neck  leads  to  the  bottom  of  the  vessel,  thus  forming  a 
continuous  passage  for  the  blast  from  the  main,  which  is  stationary,  to  the 
wind  box,  which  must  move  with  the  bottom  of  the  vessel.  To  the  other 
trunnion  is  attached  a  pinion  which  meshes  with  a  toothed  rack  that  slides 
horizontally.  By  means  of  a  double  acting  hydraulic  cylinder,  the  piston 
of  which  is  connected  to  this  rack,  the  vessel  may  be  rotated  through  an 
arc  of  270°,  the  pinion  and  rack  being  geared  so  that  the  vessel  may  be 
completely  inverted  for  dumping  slag  or  relining  the  vessel.  All  this 
mechanism  is  carefully  covered  to  protect  it  from  slag,  dust  and  other  dirt. 

Lining  of  the  Converter:  The  lining  for  the  shell  may  be  composed 
of  any  first  class  silicious  refractory  material.  At  most  works  a  highly 
silicious  sandstone,  known  as  firestone,  is  used,  while  a  mixture,  composed 
of  about  five  parts  crushed  ganister  and  one  part  best  quality  fire  clay  and 
called  ball  stuff,  serves  as  a  kind  of  mortar.  The  lining  varies  in  thickness 
from  ten  to  sixteen  inches  for  the  different  parts  of  the  vessel,  being 
thickest  on  those  parts  subject  to  the  greatest  wear.  When  lining  a  new 
vessel  or  relining  an  old  one,  the  bottom  is  detached,  the  vessel  is  inverted 
and  the  lining  is  begun  in  the  nose.  The  method  pursued  in  starting  the 
lining  will  then  depend  largely  upon  the  materials  available  and  the  shape 
of  the  vessel.  At  the  Edgar  Thomson  Works,  the  customary  procedure  is  as 
follows:  A  wooden  frame,  some  five  feet  square  and  with  a  hole  in  the  center 
of- the  same  shape  and  size  as  the  mouth  of  the  vessel,  is  laid  on  suitable 
cross  pieces  and  then  suspended  from  the  vessel  so  as  to  press  firmly  against 
the  nose  and  in  such  a  position  that  the  hole  is  superimposed  upon  the 
mouth.  In  this  way  a  ledge  upon  which  to  begin  the  wall  is  formed.  Upon 
this  ledge  is  placed  a  three  inch  layer  of  ball  stuff,  which  is  followed  by  a 
course  of  large,  flat,  undressed  firestone,  set  in  on  edge.  All  the  inter- 
stices are  rammed  full  of  wet  ball  stuff,  so  that  the  stones  are  securely 
keyed  into  place  and  the  side  and  top  present  a  smooth  surface.  Upon  this 


CONSTRUCTION  OF  THE  CONVERTER  185 

nose  wall,  which  is  about  sixteen  inches  thick  and  thirty  inches  high, 
the  body  wall  is  built.  It  consists  of  two  courses.  A  thin  course  of  split 
brick  is  laid  next  to  the  shell,  while  within  this,  the  inner  course,  about 
twelve  inches  thick,  is  built  up  of  rough  blocks  of  firestone  laid  in  a 
mortar  of  ball  stuff.  The  stones  for  the  top  course  of  this  wall  are  cut 
to  shape  and  keyed  in  so  as  to  hold  the  wall  in  place  when  the  vessel  is 
righted  and  also  to  form  a  smooth  joint,  or  shoulder,  against  which  the 
bottom  is  to  fit.  The  lining  is  now  completed  by  plastering  the  interior  of 
the  vessel  with  ball  stuff,  after  which  it  is  carefully  and  thoroughly 
dried.  The  coat  of  plaster,  aside  from  giving  a  smooth  surface,  protects 
the  stone  and  overcomes  its  tendency  to  spall.  To  prepare  the  vessel  for 
use,  the  bottom  is  put  on,  the  vessel  is  inclined,  and  then  heated  to  a  high 
temperature  with  natural  gas  fires  in  the  vessel  itself.  In  case  of  a 
shortage  or  absence  of  gas,  coke  or  wood  may  be  substituted  for  the  gas. 
With  careful  patching  this  part  of  the  lining  may  last  for  several  weeks, 
or  even  months,  of  continuous  running. 

The  Bottom  of  the  converter  warrants  special  mention.  It  is  the  part 
of  the  vessel  subject  to  the  greatest  wear  and  seldom  lasts  longer  than 
twenty  heats,  when  it  must  be  removed  for  repairs  and  replaced  by 
another.  This  change  can  be  made  with  a  delay  of  less  than  twenty 
minutes,  and  is  carried  out  in  the  following  manner:  The  bottom  of  the 
wind  box  is  removed  while  the  vessel  is  pouring,  then  as  soon  as  the  slag 
is  dumped,  the  converter  is  righted,  and  a  small  but  strongly  built  truck 
provided  with  a  hydraulic  jack,  or  lift,  is  run  beneath  it.  The  water 
connection  having  been  made  with  the  hydraulic  cylinder,  the  pressure  is 
applied  to  the  jack,  which  raises  a  small  table  against  the  bottom.  In  some 
plants  the  jack  is  placed  beneath  the  track,  in  which  case  the  whole  truck 
is  raised.  The  keys  are  next  knocked  out,  which  leaves  the  bottom  free 
to  descend  with  the  table  or  the  truck.  The  truck  is  then  pulled  into  the 
bottom  house,  where  an  overhead  crane  picks  up  the  bottom  and  carries 
it  to  one  side.  By  reversing  this  procedure,  a  new  bottom  is  soon  in 
place,  and  the  converter  is  ready  for  charging. 

Relining  the  Bottom :  The  repairing  of  the  old  bottom  is  immediately 
begun.  What  remains  of  the  old  tuyeres  and  filling  is  quickly  cooled  with 
water,  and  that  on  the  bottom  is  loosened  with  suitable  tools,  when  it  may 
be  removed  from  the  bottom  by  dumping  it  with  the  crane.  The  removal 
of  this  material  makes  it  easier  to  inspect  the  construction  of  the  bottom. 
The  shell  is  made  of  heavy  steel  plates  riveted  together  in  the  shape  of 
a  shallow  bowl  with  an  open  bottom.  Closing  this  opening  from  within 
the  bowl,  is  the  false  bottom,  a  flat  circular  casting,  with  openings  through 
which  the  tuyeres  may  be  inserted.  It  is  a  little  larger  in  diameter  than 
the  opening  which  it  closes,  thus  making  it  unnecessary  to  fasten  it  in  any 
way.  It  supports  the  bottom  stuff  in  which  the  tuyeres  are  packed. 
Covering  this  same  opening  from  without  is  the  tuyere  plate,  a  similar 
casting  containing  bevelled  openings  into  which  the  tuyeres  fit  when  in 
place.  This  plate  is  prevented  from  making  a  tight  joint  with  the  bottom 


186  BESSEMER  PROCESS 

by  means  of  the  splice  plates  that  hold  the  riveted  plates  together.  Thus, 
an  open  space  about  one  inch  in  depth  is  left  between  the  tuyere  plate  and 
the  false  bottom.  The  plate  forms  the  top  of  the  wind  box,  the  two  being 
firmly  bolted  to  each  other  and  to  the  bottom  with  the  same  bolts.  The 
side  of  this  wind  box  is  a  large  casting,  oval  in  shape,  and  about  twelve 
inches  in  depth.  The  bottom  of  the  box  is  a  steel  plate  which  is  firmly  . 
keyed  to  the  casting  to  make  an  almost  air  tight  joint  when  the  vessel  is 
blowing.  Connecting  the  wind  box  with  the  interior  of  the  bowl,  are 
nineteen  to  twenty-one  circular  bevelled  holes,  through  which  the  tuyeres 
are  inserted.  The  tuyeres  are  cylindrical  bricks,  flared  for  a  distance  of 
about  six  inches  from  one  end.  They  are  about  thirty  inches  long,  seven 
inches  in  diameter,  and  each  one  contains  about  twelve  holes,  one-half  inch 
in  diameter  and  extending  longitudinally.  To  place  a  tuyere,  the  flare  is 
covered  with  a  mortar,  composed  of  fire  clay  and  Portland  cement,  and 
the  tuyere  is  inserted  upward  through  the  opening  in  the  bottom,  where 
it  is  held  in  place  with  clamps  until  the  filling  has  been  put  in.  When  all 
the  tuyeres  have  been  thus  placed  in  position,  the  top  of  each  is  covered 
with  a  metal  plate  to  keep  dirt  out  of  the  tubes,  some  bottom  stuff 
is  placed  on  the  bottom  in  the  space  around  the  tuyeres,  and  on  this 
large  tiles  are  set  in  as  reinforcement  to  the  tuyeres.  The  space  remaining 
about  the  tuyeres  and  brick  is  then  tamped  full  with  more  of  the  bottom 
stuff,  which  is  a  moist  mixture  composed  of  28  parts  crushed  ganister,  12 
parts  blue  fire  clay,  3  parts  ground  brick  bats,  3  parts  old  bottom  stuff 
and  4  parts  coke  dust.  The  bottom  is  then  pushed  into  a  drying  oven, 
fired  with  coke  oven  gas,  and  carefully  dryed,  then  finally  baked  for  several 
hours.  The  time  required  to  dry  and  bake  a  bottom  properly  is  about 
forty-eight  hours,  though  bottoms  will  often  be  used  at  the  end  of  thirty- 
six  hours.  Upon  being  required  for  use,  it  is  withdrawn  from  the  oven, 
and  a  heavy  layer  of  a  stiff  clay  mixture  is  placed  around  the  upper  edge  to 
form  a  tight  joint  with  the  shoulder  of  the  vessel  when  the  bottom  is  in 
place.  The  mortar  is  then  sprinkled  heavily  with  coke  dust,  after  which 
the  bottom  is  put  into  service  as  previously  described.  The  function .  of 
the  coke  dust  is  to  prevent  the  bottom  from  cementing  itself  to  the 
shoulder  joint.  When  in  service  the  position  of  the  bottom  is  such  that 
the  long  axis  of  the  oval  wind  box  is  parallel  to  the  axis  of  rotation  of  the 
vessel.  The  advantage  of  this  shape  is  obvious,  for  it  is  easily  seen  that 
with  the  wind  box  in  this  position  a  greater  volume  of  metal  may  be  held  in 
the  vessel  while  in  the  horizontal  position  without  filling  the  tuyeres  than 
would  be  possible  with  a  round  box,  which  is  the  form  used  on  eccentric 
vessels.  The  double  bottom,  mentioned  above,  is  also  of  great  advantage. 
Since  the  space  between  the  upper  and  lower  plates  connects  with  the  outside, 
it  not  only  gives  warning  of  a  worn  out  tuyere,  but  also  prevents  the  wind 
box  from  being  filled  with  hot  metal  in  case  of  a  break  out.  When  a 
tuyere  becomes  defective  or  badly  and  dangerously  worn  during  a  blow, 
it  may  be  plugged  by  turning  the  vessel  down,  removing  the  wind  box  lid, 
and  stopping  its  openings  with  clay. 


PURIFYING  THE  METAL  187 

SECTION   V. 

THE   CONVERTER  IN   OPERATION — PURIFYING  THE   METAL. 

Charging  the  Vessel:  With  the  bottom  fastened  in  place  and  the 
vessel  at  the  proper  temperature,  it  is  ready  for  the  charge.  The  charging 
is  a  matter  of  much  importance.  Besides  being  a  factor  in  determining 
the  composition  or  grade  of  steel  produced  with  respect  to  phosphorus  and 
sulphur,  it  also  offers  a  means  of  controlling  the  temperature  during  the 
blow.  It  must  always  be  predetermined  by  the  blower,  who  has  charge 
of  the  blow.  In  acid  practice  the  charge  consists  of  molten  pig  iron, 
to  which  is  added  cold  pig  iron  or  steel  scrap  in  amounts  sufficient  to  meet 
the  heat  requirements  of  the  blow.  As  the  only  source  of  heat  is  the 
oxidation  of  the  iron,  silicon,  manganese  and  carbon,  the  composition  of 
the  pig  iron  is  important,  and  the  blower  must  be  kept  informed  in  advance 
as  to  the  composition  of  the  iron.  In  operating  a  hot  vessel  on  hot  iron 
there  is  much  more  heat  generated  than  is  required  to  keep  the  metal 
molten,  in  which  case  the  temperature  may  be  kept  under  control  by 
charging  steel  scrap.  Scrap  may  be  added  to  the  heat  at  any  time  during 
the  first  part  of  the  blow.  The  addition  of  scrap  also  has  the  advantage 
of  increasing  the  output.  In  beginning  on  a  new  lining  or  a  new  bottom, 
or  after  a  delay,  the  vessel  will  be  cold  and  will,  itself,  absorb  much  heat, 
which  condition  precludes  the  use  of  cold  materials  in  the  charge.  In  an 
attempt  to  lessen  the  loss  of  iron  through  oxidation  and  shorten  the  time 
of  a  blow,  roll  scale  or  other  oxides  of  iron  are  often  charged. '  Such  additions 
may  reduce  the  blowing  period  by  about  one-third,  and  are  made  regularly 
at  some  plants,  but  this  is  not  the  practice  at  Edgar  Thomson.  On  making 
a  steel  that  requires  a  high  sulphur  content,  like  screw  steel,  the  required 
amount  of  this  element,  in  the  form  of  pyrite,  may  be  added  along  with 
the  molten  metal.  The  blower,  having  been  informed  as  to  the  require- 
ments of  the  rolling  mills,  decides  upon  the  charge  best  suited  to  the  con- 
ditions, then  sends  an  order  to  the  mixer  for  a  certain  weight  of  pig  iron. 
At  these  works  this  amount  will  vary  from  30,000  to  36,000  pounds.  The 
molten  iron  is  weighed  at  the  mixer  as  it  is  poured  into  the  ladle,  the  truck 
of  which  sets  on  a  scale  platform.  Some  coke  breeze  is  then  thrown  upon 
the  molten  metal  to  keep  it  from  skulling  the  ladle,  when  it  is  taken  by 
a  dinkey  to  the  charging  floor  of  the  converter.  Here,  the  vessel  is  turned 
down  to  a  horizontal  position,  so  as  to  bring  the  tuyeres  well  above  the 
bath,  and  the  molten  iron  is  poured  into  the  mouth  of  the  vessel  by  slowly 
tipping  the  ladle.  The  scrap  is  added  from  the  scrapping  floor  shortly  after 
the  vessel  is  brought  to  the  vertical  position. 

The  Blow:  Immediately  after  the  vessel  has  received  the  charge  of 
molten  metal,  the  blast,  under  a  pressure  sufficient  to  prevent  the  metal 
from  flowing  into  the  tuyeres  and  also  force  the  air  through  the  liquid,  is 
turned  on,  and  the  vessel  is  racked  to  the  vertical  position.  With  this  act 
the  air  of  the  blast  is  forced  to  pass  up  through  the  molten  mass,  and 
chemical  action  between  the  oxygen  of  the  air  and  the  various  ingredients 


188  BESSEMER  PROCESS 

of  the  metal  immediately  begins.  This  oxidation  takes  place  in  successive 
stages,  each  of  which,  provided  the  blow  is  a  normal  one,  produces  its 
own  peculiar  effect  in  the  metal  and  upon  the  kind  of  matter  ejected  from 
the  mouth  of  the  vessel.  Their  order,  therefore,  may  be  followed  by  the 
naked  eye  or  through  colored  glasses.  As  the  vessel  is  righted  a  shower 
of  sparks  is  emitted  from  its  mouth.  Then  a  stream  of  dense  brown  fumes 
pours  forth,  to  be  succeeded  shortly  by  a  dull  red,  short,  pointed  flame 
that  protrudes  from  the  mouth  of  the  vessel.  This  action  occupies  but 
five  or  six  minutes,  when  this  flame  is  gradually  replaced  by  a  short  luminous 
one  that  plays  about  the  mouth.  This  flame  soon  begins  to  increase,  both 
in  length  and  luminosity,  until  it  has  reached  a  maximum  length  of  thirty 
feet  or  more,  which  it  maintains  steadily  for  about  eight  minutes.  During 
this  period,  known  as  the  boil,  a  dull  roaring  coming  from  the  vessel  may  be 
heard.  This  noise  is  caused  by  the  violent  agitation  of  the  bath  by  the 
blast  and  the  rapid  generation  of  carbon  monoxide  gas  within  it.  Just 
before  the  end  of  the  blow,  the  flame  begins  to  drop,  or  "die,"  that  is,  it  suddenly 
becomes  less  luminous,  giving  an  effect  similar  to  that  to  be  expected  if  a 
smoked  glass  or  a  cloud  were  placed  between  it  and  the  eye;  and  if  it  is  being 
observed  through  blue  glasses,  purple  streaks  are  visible  in  it.  If  the  blow 
should  be  continued,  this  flame  would  disappear  entirely,  but  the  metal  is 
always  poured  before  this  point  is  reached.  Thus,  the  entire  time  required 
to  convert  fifteen  to  eighteen  tons  of  pig  iron  into  steel  is  only  about  fifteen 
minutes. 

Controlling  the  Blow:  The  appearance  of  the  flame  just  described 
serves  as  an  index  to  the  change  going  on  in  the  vessel,  and  so  is  very 
important  to  the  blower,  upon  whom  rests  the  responsibility  for  the  proper 
operation  of  the  vessel.  He  is  also  held  accountable  for  the  quality  of 
the  steel  he  produces.  He  has  an  assistant  who  turns  the  vessel  for  charging 
and  pouring  and  operates  the  ladle  crane,  but  the  control  of  the  process 
is  in  the  hands  of  the  blower  himself.  He  must  decide  the  best  proportions  of 
hot  metal  and  scrap  to  use,  regulate  the  temperature,  determine  the  time 
for  turning  down  and  over-see  the  recarburizing  of  the  blown  metal.  AS 
to  the  kind  of  recarburizer  and  the  amount  to  use  per  ton  of  steel,  he  receives 
instructions  from  his  superintendent's  office.  Factors  that  enter  into  the 
making  up  of  the  charge  have  already  been  explained.  The  importance  of 
a  high  temperature  was  also  alluded  to  as  necessary  to  keep  the  bath  molten. 
In  this  connection  it  remains  to  be  pointed  out  that  temperature  is  an 
important  factor  in  controlling  the  blow,  and  so  exerts  an  influence  on  the 
quality  of  the  product.  As  it  is  impossible  to  regulate  the  charge  so  as 
to  meet  all  the  variations  in  the  conditions,  other  means  of  regulating 
the  temperature  must  be  resorted  to  during  the  blow  itself.  To  raise  the 
temperature  after  a  blow  is  in  progress,  the  vessel  may  be  turned  so  as 
to  expose  a  few  tuyeres  above  the  metal.  The  combustion  of  the  carbon 
monoxide  gas  over  the  bath  generates  heat,  which  raises  the  temperature 
of  the  vessel  and  consequently  of  the  metal  also.  This  method  wastes 
some  metal,  as  iron  is  excessively  oxidized.  Ferro  silicon  is  also  used  for 


PURIFYING  METAL  189 

this  purpose,  the  oxidation  of  the  silicon  being  the  source  of  heat  in  this 
case.  Either  method  is  expensive  and  should  be  avoided.  With  rapid 
working,  and  with  iron  of  proper  grade,  cold  heats  are  the  exception, 
occurring  mainly  on  new  linings  or  in  the  first  blow  on  a  new  bottom.  To 
lower  the  temperature  is  a  much  easier  matter.  The  vessel  may  be  tilted 
and  allowed  to  cool  by  radiation,  or  cold  metal  in  the  form  of  steel  scrap 
may  be  added,  if  the  heat  is  not  too  far  advanced.  A  more  convenient 
method  is  that  of  introducing  steam  with  the  blast,  and  as  it  is  very  con- 
venient, it  is  often  employed.  The  water  coming  in  contact  with  the 
highly  heated  metal  is  decomposed  according  to  the  following  reaction: 
H2O+Fe=FeO+H2.  Steam  thus  introduced  is  not  very  efficient  because 
the  oxidation  due  to  air  is  not  retarded  and  very  little,  if  any,  heat  can  be 
absorbed.  However,  less  heat  is  generated  in  oxidizing  iron  with  water  than 
with  air,  besides,  steam  is  easily  controlled,  is  always  at  hand,  and  can  be 
introduced  in  varying  amounts  without  delay  to  the  blow  or  turning  the 
vessel.  The  blower  will,  then,  keep  close  watch  on  the  flame,  and  introduce 
steam  during  the  blow  as  often  as  required  to  hold  the  temperature  at  the 
proper  level.  The  speed  of  the  blow,  and,  indirectly,  the  temperature,  may 
be  controlled  to  a  limited  extent,  also,  by  varying  the  blast  pressure.  In 
this  connection  it  should  be  stated  that  there  are  so  many  variables  con- 
nected with  the  operations  that  no  uniform  method  can  be  established. 
Even  with  metal  of  uniform  composition  and  other  conditions  apparently 
alike,  two  consecutive  heats  made  to  the  same  specification  will  seldom 
require  the  same  manipulation.  Thus,  the  success  of  the  entire  operation 
depends  upon  the  judgment  of  the  blower. 

The  End  of  the  Blow:  Owing  to  the  rapidity  of  the  reactions  and  other 
peculiar  conditions,  the  composition  of  the  steel  cannot  be  well  regulated  by 
stopping  the  blow.  While  it  is  possible  to  blow  a  heat  to  approximately  any 
carbon  content  desired,  the  method  is  not  practiced  in  America,  because  it 
slows  down  the  operation  too  much.  It  is  much  cheaper  and  surer,  therefore, 
to  blow  full,  and  add  both  carbon  and  manganese  with  the  recarburizer. 
Xhis  is  the  practice  at  Edgar  Thomson.  At  these  works,  if  the  blow 
is  stopped  at  the  first  indication  of  the  drop  of  the  flame,  it  is  said  to 
be  turned  down  young;  if  continued  till  the  drop  is  pronounced,  the  blow  is 
full.  In  either  case  the  silicon  will  have  been  completely  eliminated,  while 
only  small  amounts  of  manganese  and  carbon  will  remain.  The  residual 
manganese  may  be  as  high  as  .06  or  .08%,  depending  upon  the  extent  of  the 
blow  and  the  percentage  in  the  pig  iron.  If  the  blow  is  turned  down  young, 
.08%  to  .10%  carbon  will  remain,  while  in  a  full  blow  this  amount  is 
decreased  to  .03  or  .04%.  The  percentage  of  phosphorus  and  sulphur  is 
slightly  higher  than  in  the  original  pig  iron,  owing  to  a  loss  in  weight  due 
to  oxidation  and  elimination  of  the  silicon,  carbon,  manganese  and  part  of 
the  iron,  and  also  to  the  ejection  of  metallic  iron  from  the  vessel.  The 
total  loss  will  amount  to  something  between  8%  and  10%  of  the  charge, 
nearly  half  of  which  is  oxide  of  iron  and  manganese  which  can  be  recovered 
by  using  the  slag  in  the  blast  furnace. 


190 


BESSEMER  PROCESS 


SECTION   VI. 

FINISHING   OPERATIONS CONVERTING   THE   PURIFIED    METAL   INTO    STEEL. 

Deoxidation  and  Recarburization  must  always  immediately  follow 
the  blow.  At  Edgar  Thomson  this  is  done  in  the  ladle  as  the  metal  is  being 
poured,  though  at  certain  other  plants  some  of  the  additions  are  made  in 
the  vessel.  In  general  the  objects  sought  are:  1st.,  control  of  the  carbon 
content;  2d.,  deoxidation  of  the  steel;  and  3d.,  introduction  of  elements, 
such  as  manganese,  to  improve  the  quality  of  the  steel.  The  following 
table  shows  the  difference  in  the  analysis  of  steel  before  and  after  recar- 
burizing,  and  partly  illustrates  the  many  grades  produced. 

Table  29.     Showing  Chemical  Relation  of  Purified  Metal  to 
Different  Grades  of  Steel. 


Kind  of 
Steel 

Per  Cent. 
Carbon 

Per  Cent. 
Manganese 

Per  Cent. 
Sulphur 

Per  Cent. 
Phosphorus 

As  Blown..  . 

.03  to  .10 

Trace  to  .06 

.03  to  .06 

.08  to  .100 

Skelp 

Not  over  .08 

.30  to  .40 

Not  over  .06 

Not  over  .100 

Sheet  Bar.  . 

"       "     .10 

.30  to  .50 

"     .06 

"     .100 

Screw  Steel. 

"      .08 

.60  to  .80 

Not  under  .085 

"      .100 

Special 

Billet  Steel 

.25  to  .30 

.40  to  .50 

Not  over  .085 

'4     .100 

Light  Splice 

Bar  

.08  to  .10 

.35  to  .60 

"     .06 

"      .100 

Rail  Steel.  . 

.30  to  .50 

.70  to  1.10 

"     .06 

"      .100 

Needless  to  say,  the  different  grades  of  steel  require  different  methods 
of  recarburizing  to  meet  the  requirements,  which  fact  calls  for  different 
recarburizers.  The  various  recarburizers  and  deoxidizers  most  commonly 
employed  are  ferro  manganese,  spiegel,  anthracite  coal,  ferro-silicon, 
and  pig  iron,  analyses  of  representative  samples  of  which  are  given  in  the 
subjoined  table. 

Table  30.     Analyses  of  Representative  Samples  of  Deoxidizers 
and  Recarburizers. 


Per  Cent. 
Iron 

Per  Cent. 
Carbon 

Per  Cent. 
Manga- 
nese 

Per  Cent. 
Sulphur 

Per  Cent. 
Phos- 
phorus 

Per  Cent. 
Silicon 

Per  Cent. 
Ash 

Ferro  Manganese.  . 
Spiegel 

11.95 
73  20 

6.50 
5  00 

80.40 
°0  40 

Trace 

.160 
100 

1.00 
1  10 

Ferro-Silicon 

86  70 

2  00 

50 

050 

080 

10  60 

Pig  Iron.  .  .  . 

93  05 

4  50 

67 

047 

088 

1  67 

Anthracite  Coal.  .  . 

85.50* 

4  50 

*Fixed  carbon  only. 


FINISHING  THE  BLOW  191 


Loss  of  Recarburizer  and  Deoxidizer:  In  adding  the  recarburizers, 
a  loss  always  takes  place,  for  which  an  allowance  must  be  made.  The 
amount  of  this  loss  is  fairly  uniform  under  similar  conditions,  and  is  deter- 
mined by  experience.  In  the  case  of  manganese  it  amounts  to  about  20% 
of  the  manganese  added  for  full  blown  heats,  in  which  the  per  cent,  of 
manganese  does  not  exceed  .60.  The  loss  is  somewhat  less,  not  over  15%, 
if  the  blow  is  stopped  young.  The  loss  varies,  also,  with  the  amount  of 
manganese  added,  increasing  rapidly  as  the  per  cent,  in  the  steel  is  raised 
above  .60.  Similar  data  is  required  in  using  ferro-silicon  and  anthracite 
coal,  the  loss  of  carbon  in  using  the  latter  being  about  50%  of  the  total 
amount  added. 

^Examples  of  Recarburizing:  Some  simple  examples  of  recarburizing 
will  illustrate  the  methods  employed.  1.  Suppose  it  is  required  to 
produce  a  soft  steel,  such  as  the  skelp  shown  in  the  table  above.  The 
metal  will  be  given  a  full  blow  to  reduce  the  carbon  content  to  about  .04%, 
and  hot  ferro  manganese  will  be  added  in  sufficient  quantity  to  raise  the 
per  cent,  of  this  element  to  .40.  A  simple  calculation,  if  proper  allowance 
is  made  for  both  residual  manganese  and  manganese  lost,  will  show  that 
this  amount  of  ferro  will  raise  the  per  cent,  of  carbon  to  .08.  2.  In  the 
case  of  a  medium  soft  steel,  say  .20%  to  .25%  C.,  .40%  to  .50%  Mn.,  the 
recarburization  after  a  full  blow  may  be  made  with  molten  Spiegel  mixture 
containing  about  12%  Mn.  and  5%  C.,  or,  as  it  is  difficult  to  handle  and 
weigh  small  amounts  of  molten  metal,  coal  and  ferro-manganese  are  more 
often  used.  In  the  latter  case,  the  blow  may  be  turned  down  young.  3. 
In  the  case  of  a  rail  heat  the  blow  is  turned  down  young,  and  recarburized 
with  molten  spiegel  mixture.  Molten  pig  iron  and  ferro  manganese  could 
also  be  used,  but  this  is  not  the  practice  at  the  Edgar  Thomson  Bessemer 
plant.  At  this  plant  the  cupola  charge  for  the  spiegel  mixture  used  to 
recarburize  rail  heats  consists  of  spiegel,  ferro  silicon,  and  pig  iron,  in 
proportion  to  produce  a  mixture  containing  12%  Mn.,  4.50%  C.,  and  1.50% 
Si.  For  determining  the  quantity  of  deoxidizer  and  recarburizer  to  add, 
the  blower  is  provided  with  a  set  of  factors,  one  for  each  grade  of  steel 
produced,  the  numerical  values  of  which  are  fixed  by  experience.  Thus, 
for  sheet  bar  the  factor  giving  the  amount  of  80%  ferro  manganese  to  add, 
is  .0045,  but  for  skelp  it  is  .0055  because  this  steel  is  blown  very  full. 
Similarly,  factors  for  finishing  rail  steel  with  spiegel  are  given. 

Ladle  Reaction :  The  addition  of  the  recarburizer  is  usually  followed 
by  a  violent  boiling  of  the  metal  in  the  ladle,  causing  much  slag  to  be 
thrown  out  over  the  sides.  This  is  often  referred  to  as  the  spiegel  reaction 
or  ladle  reaction.  With  the  addition  of  the  recarburizer,  precautions 
will  be  taken  to  mix  it  thoroughly  with  the  metal.  At  Edgar  Thomson 
this  mixing  is  accomplished  in  the  case  of  rail  heats  by  using  molten 


192  BESSEMER  PROCESS 

spiegel    and  pouring  it  into  the  ladle   with   the   metal   from  the   vessel, 
and  in  the  case   of  soft  steels  by  poling  the  metal  in  the  ladle. 

Teeming:  The  history  of  the  heat  may  now  be  resumed.  Soon  after 
the  recarburizer  has  been  added,  the  pouring  of  the  metal  will  have  been 
completed.  The  converter  is  then  inverted,  and  the  slag  which  did  not 
flow  out  with  the  metal  is  dumped  upon  a  small  flat  car  beneath  the  vessel, 
which  is  then  ready  for  the  next  charge.  While  this  is  going  on,  the  steel 
has  become  quieter  in  the  ladle  and  has  been  raised  to  the  proper  level 
by  the  steel  crane,  which  then  transfers  it  to  the  teeming  table  in  front 
of  the  pouring  platform.  Here  the  teeming  hole  in  the  bottom  of  the  ladle 
is  opened  by  removing  the  small  plate  and  digging  out  the  sand,  when 
the  metal  may  be  allowed  to  flow  at  will  by  raising  and  lowering  the  stonper 
lever.  The  metal  is  now  teemed,  consecutively,  into  four  ingot  moulds, 
which  have  been  prepared  as  previously  described.  As  each  mould  is  filled 
to  the  mark,  the  next  is  moved  under  the  nozzle  by  means  of  the  "dog," 
hydraulically  operated  and  provided  for  the  purpose.  During  the  teeming 
of  each  ingot  of  soft  or  medium  soft  steel,  small  pieces,  about  four  ounces  in  all, 
of  aluminum  may  be  added,  as  the  judgment  of  the  teemer  directs,  to  assist 
in  further  deoxidizing  the  steel.  This  metal  will  always  be  added  if  the 
steel  is  very  wild,  which  condition  is  often  found  in  soft  steel  made  by 
this  process.  After  all  the  steel  has  been  teemed  into  the  moulds,  the 
little  train  is  pushed  along  the  track  to  the  end  of  the  teeming  platform, 
where  the  ingots  are  allowed  to  cool.  If  the  ingots  show  a  tendency  to 
grow  in  the  moulds,  the  tops  may  be  sprayed  with  water,  and  heavy  caps 
of  cold  iron  will  be  placed  on  them.  This  treatment  is  intended  to  chill  the  top 
and  stop  the  growing,  which  invariably  increases  the  number  and  size  of  the 
blow  holes  and  pipe  in  the  top  of  the  ingot.  Growing  is  peculiar  to  soft 
steels;  rail  heats  seldom  exhibit  this  tendency.  When  the  ingots  have 
cooled  sufficiently  to  form  a  thick,  strong  shell  on  the  outside,  they  are 
taken  to  the  stripper,  where  the  moulds  are  at  once  removed.  This  done, 
they  are  ready  for  the  soaking  pits,  which  are  more  properly  treated  under 
rolling  mills. 

Sampling  the  Steel  for  Chemical  Analyses:  A  sample  for  chemical 
analysis  is  taken  during  the  teeming  of  each  heat.  This  matter  is  of  much 
importance,  and  has  received  the  attention  it  deserves.  The  sample  is 
obtained  when  half  of  the  ladle  of  steel  has  been  teemed  by  holding  a  large 
steel  spoon  beneath  the  nozzle  and  allowing  a  small  stream  of  the  metal 
to  flow  therein  until  the  spoon  is  full.  This  metal  is  then  poured  from  the 
spoon  into  a  specially  constructed  mould  where  it  is  allowed  to  cool  or  set, 
after  which  it  is  stamped  with  the  heat  number  and  is  then  taken  to  the 
chemical  laboratory  for  analysis.  Everything  has  been  done  to  insure 
this  sample  is  truly  representative  of  the  whole  heat,  which  is  seldom  true 
of  samples  taken  in  other  ways. 


CHEMISTRY  OF  193 


SECTION   VII. 

CHEMISTRY  OF  THE   PROCESS. 

The  Order  of  Elimination  of  the  Elements :  As  previously  indicated, 
the  heat  required  for  the  process  is  generated  by  the  oxidation  of  the  iron 
and  the  metalloids,  silicon,  manganese,  and  carbon.  An  examination  of 
the  blow  will  show  that,  during  the  first  period,  the  oxygen  of  the  blast 
attacks  first  the  iron,  then,  both  directly  and  indirectly,  as  will  be  explained 
shortly,  the  silicon  and  manganese,  producing  exothermic  reactions  which 
rapidly  increase  the  temperature  of  the  bath.  The  converter  gases  during 
this  period  are  mainly  nitrogen  with  some  carbon  dioxide  and  traces 
of  oxygen  and  hydrogen.  These  reactions  produce  no  flame,  since  all  the 
products  of  the  oxidation  are  solids,  but  with  the  rise  in  temperature, 
carbon  begins  to  be  oxidized  to  carbon  monoxide,  which  will  burn  at  the 
mouth  of  the  vessel  to 'carbon  dioxide  and  produce  a  flame  outside  the 
vessel.  So,  the  heat  generated  by  combustion  of  the  CO  to  CO2is  wasted. 
The  rapid  generation  of  CO  in  the  metal  produces  the  "boil,"  and  the 
increasing  speeds  at  which  the  formation  of  this  gas  takes  place  causes 
the  flame  to  grow  to  a  maximum  size  and  finally  subside  with  the  elimi- 
nation of  the  carbon.  The  escaping  gases  during  this  period  consist  mainly 
of  nitrogen  and  carbon-monoxide  with  small  percentages  of  carbon  dioxide 
and  traces  of  hydrogen.  Thus,  at  no  time  during  the  blow,  except  for  a 
short  period  at  the  beginning,  does  any  but  traces  of  the  oxygen  of  the  air 
escape  from  the  bath  uncombined,  though  the  layer  of  metal  is  but  some 
twenty  inches  thick,  and  the  volume  of  the  blast  is  more  than  6000  cubic  feet 
per  minute.  This  fact  is  not  surprising,  if  it  is  remembered  that  the  temper- 
ature of  the  bath  from  the  first  is  much  above  the  kindling  temperature 
for  any  element  in  the  bath,  and  that  the  blast  is  delivered  by  the  tuyeres 
almost  in  the  form  of  a  spray.  Under  these  conditions,  the  combination 
of  these  elements  with  oxygen  must  be  almost  instantaneous,  resulting  in 
all  the  oxygen  being  consumed  at  the  mouth  of  the  tuyere.  Concerning 
the  brownish  fumes  ejected  by  the  converter,  especially  at  the  beginning 
of  a  blow,  various  suppositions  have  been  advanced  to  account  for  them. 
It  has  been  suggested  that  they  may  be  volatile  compounds  of  iron  and 
manganese  with  carbon,  which,  upon  coming  in  contact  with  the  air  at  the 
mouth  of  the  vessel,  are  immediately  oxidized,  the  metallic  oxides  producing 
the  brown  color.  Analysis  of  deposits  made  by  this  fume  have  been  made, 
and  they  are  found  to  be  composed  roughly  of  one  part  ferrous  oxide,  two  parts 
silica  and  three  parts  manganese  oxide.  Manganese  is  volatile  at  a  compara- 
tively low  temperature,  which  fact  may  account  for  a  part  of  the  fume, 
but  with  respect  to  iron  and  silicon  or  silica,  the  most  plausible  explanation 
is  that  they  are  carried  out  mechanically  in  a  finely  divided  state  by  the 
blast. 

The  Laws  and  Conditions  Governing  the  Reactions  in  the  Con- 
verter: A  review  of  the  laws  of  chemical  action  and  of  the  conditions  of 


194  BESSEMER  PROCESS 

the  blow  will  render  an  explanation  of  the  changes  that  take  place  to  bring 
about  the  results  enumerated  above  very  easily  understood.  If  reference 
be  made  to  the  laws  controlling  chemical  action  in  Chapter  I.,  it  will  be 
found  that, under  normal  conditions  of  blowing  metal,  only  two  are  applicable 
to  the  matter  under  consideration.  One  of  these,  the  law  of  mass  action, 
states,  in  effect,  that  the  rate  or  speed  of  a  chemical  reaction  may  be 
increased  by  increasing  the  active  masses,'  or  amounts,  of  the  reacting 
substances;  and  the  other  law  says  that  when  chemical  reactions  take 
place  without  the  aid  of  heat  supplied  from  an  external  source,  those  sub- 
stances which  have  the  greatest  heats  of  formation,  that  is,  those  that 
give  off  the  most  energy,  will  tend  to  form.  As  to  the  conditions,  these 
can  be  very  briefly  and  simply  stated.  They  are,  that  at  the  beginning  of 
the  blow  the  bath  represents  a  solution  of  approximately  4  parts  carbon, 
1.5  parts  silicon,  1  part  manganese,  .1  part  phosphorus  and  .05  parts  sulphur 
in  93.35  parts  iron  at  a  temperature  that  is  several'degrees,  say  100°,  above 
the  fusion  point  of  the  mixture;  but  this  temperature  is  rapidly  raised 
during  the  first  part  of  the  blow.  The  phosphorus  and  sulphur  are  not 
affected,  so  they  need  not  be  considered,  but  the  elimination  of  the  other 
impurities  presents  an  interesting  study. 

Reactions  of  the  First  Period :  Chemical  knowledge  does  not  tolerate 
the  idea  that  these  impurities  are  oxidized  by  the  action  of  oxygen  directly, 
but  indicates  that  the  reactions  occurring  at  the  beginning  of  the  blow  are 
governed  by  the  law  of  mass  action.  According  to  this  law,  iron,  by  far 
the  most  abundant  element  present,  is  first  oxidized  almost  to  the  entire 
exclusion  of  the  other  three  elements.  This  reaction,  which  liberates  a 
large  amount  of  heat,  is  represented  thus! 

(1)  2  Fe+O2=2  FeO  (+131400  cal.) 
2  (65700  cal.) 

With  the  oxidation  of  the  iron  to  FeO,  this  oxide,  being  soluble  in  the  metal, 
is  distributed  throughout  the  bath,  and  the  oxidation  of  the  silicon  and 
manganese  take  place  in  the  order  of  the  heats  of  formation  of  their  oxides, 
as  shown  in  the  following  reactions: 

(2)  2  FeO    +Si=SiO2+2Fe     (+64600  cal.) 
Heats  of  formation:— 2(65700  cal. )  +  (196000  cal.) 

(3)  FeO+Mn=MnO+Fe     (+25200  cal.) 
Heats  of  formation:— 65700  cal.        +90900  cal. 

With  the  oxidation  of  silicon  and  manganese,  a  slag  is  immediately  formed 
by  the  combination  of  silica  with  the  excess  FeO  and  the  MnO  according 
to  the  following: 

(4)    FeO    +  SiO2       =      FeO.SiO2     (+9300  cal.) 
Heats  of  formation :-^65700  cal.— 196000  cal.  +271000  cal. 

(5)  MnO  +  SiO2      =      MnO.SiO2    (+5400  cal.) 
Heats  of  formation:— 90900  cal.— 196000  cal.  +292300  cal. 


CHEMISTRY  OF   THE  PROCESS  195 

In  comparing  the  ratio  of  acids  to  bases  as  determined  by  actual  analysis 
with  ratios  calculated  from  formulas,  evidence  is  obtained  that  the  slag 
is  made  up,  in  part  at  least,  of  trisilicates,  in  which  case  these  reactions 
would  be  represented  thus: 

(4  A)  2  FeO+3  SiO2=(FeO)2-(SiO2)3 
(5  A)  2  MnO+3  SiO2=(MnO)2-(SiO2)3 

This  slag,  itself  a  solution  of  the  two  silicates  thus  formed,  will  dissolve 
some  of  the  FeO,  and  being  mixed  with  metal  by  the  violent  agitation  of 
the  bath,  will  also  help  to  oxidize  the  impurities.  Reactions  (1)  and  (4) 
also  account  for  the  rapid  wearing  away  of  the  bottom.  This  period  is 
then  preeminently  one  of  slag  formation.  Some  carbon,  especially 
toward  the  end  of  the  period,  however,  may  be  oxidized  directly  to  CO 
and  then  to  CC>2  by  the  FeO,  thus: 

(6)  2C+O2=    2  CO  (+29160  cal.) 

29160  cal. 

(7)  FeO     +CO    =Fe+CO2  (+2540  cal.) 
—65700  cal.— 29160  cal. +97200  cal. 

These  reactions  account  for  the  presence  of  both  CO2  and  CO  in  converter 
gases  during  the  first  part  of  the  blow.  At  the  beginning  of  the  blow,  CO 
is  subject  to  reduction  by  both  silicon  and  manganese,  especially  if  the 
iron  contains  a  high  per  cent,  of  these  elements. 

(8)  2  CO+Si=SiO2+2C  (+137680  cal.) 
—2(29160)  cal. +  196000  cal. 

(9)  CO       +Mn=MnO+C  (+71740  cal.) 
—29160  cal.  +        90900  cal. 

Reactions  of  Second  Period:  With  the  elimination  of  silicon  and 
manganese,  reaction  (8)  and  (9)  cannot  take  place.  Furthermore,  the  rise 
in  temperature  brings  about  reaction  (10)  or  (10A). 

(10)  FeO      +C=Fe+CO    (—36540  cal.), 
—65700  cal.  +29160  cal. 

(10A)      FeO+Fe3C=4Fe+CO  (— 45000  cal.) 
—65700  cal.— 8460  cal.     +29160  cal. 

These  reactions,  in  conjunction  with  reaction  (6),  rapidly  burn  out  the 
remaining  carbon.  According  to  the  law  involving  heats  of  formation,  these 
reactions  should  not  take  place,  and  it  becomes  necessary  to  explain  certain 
apparent  exceptions.  At  ordinary  temperatures  the  law  has  no  exceptions, 
but  at  elevated  temperatures  it  holds  true  through  certain  ranges  of  tem- 
perature only,  so  that,  as  the  temperature  in  any  particular  case  is  raised,  a 
point,  which  may  be  called  the  critical  temperature,  is  reached,  where  the 
energy  supplied  from  the  external  source  overbalances  that  absorbed  by  the 
reaction.  The  law  then  becomes  reversed,  and  the  reaction  proceeds  in  a 
direction  that  will  absorb  the  excess  heat.  This  fact  suggests  the  possi- 
bility that  with  hot  iron,  that  is,  iron  high  in  silicon,  which  is  also  initially 


196  BESSEMER  PROCESS 


at  a  very  high  temperature,  it  might  be  possible  to  eliminate  the  carbon 
before  the  silicon  and  manganese  could  be  oxidized,  and  the  testimony  of 
the  older  and  more  experienced  operators  of  converters  is  to  the  effect  that 
just  such  a  result  as  this  has  often  occurred  when  the  conditions  noted 
were  present.  Furthermore,  in  the  elimination  of  the  carbon,  the  law 
of  mass  action  here  becomes  prominent  again,  for  with  the  elimination  of 
the  silicon  and  manganese  the  active  mass  of  the  ferrous  oxide  rapidly 
increases  until  a  second  equilibrium  is  established,  this  time  with  carbon. 
The  reaction  is  also  probably  influenced  by  the  volatility  of  the  carbon 
monoxide,  one  of  the  products  of  the  reaction.  Comparatively  little  heat 
is  available  in  the  bath  during  this  period.  The  net  heat  generated  is  the 
difference  between  the  heat  of  formation  of  FeO  (65700  cal.)  and  that 
absorbed  in  reaction  (10)  (36540  cal),  or  29160  cal.  which  is  the  heat  of 
formation  for  CO.  The  carbon  reaction  occurs  concurrently  with  the 
phenomenon  commonly  spoken  of  as  the  boil.  There  is,  during  this  period, 
very  little,  if  any,  iron  oxidized  above  that  required  to  eliminate  the  carbon, 
so  each  volume  or  molecule  of  oxygen  in  the  blast  will  produce  two  volumes 
or  molecules  of  CO.  The  converter  gases,  therefore,  show  a  high  content 
of  CO,  very  little  CO2  and  a  marked  decrease  in  N2-  The  phosphorus 
and  sulphur  suffer  no  oxidation  from  the  action  of  FeO  until  all  but  traces 
of  carbon  is  eliminated,  and  then  only  in  the  presence  and  under  the 
influence  of  a  strong  base,  such  as  lime.  If  the  loss  in  weight  in  the  bath 
be  taken  as  10%,  then  steel  made  from  iron  containing  .045%  sulphur  and 
.089%  phosphorus  would  show  approximately  .050%  sulphur  and  .100% 
phosphorus  immediately  after  the  blow.  These  percentages  are  affected 
but  slightly  by  the  recarburizer. 

Chemistry  of  Recarburizing  and  Deoxidizing:  The  importance  of 
this  part  of  the  operation  is  more  fully  appreciated  when  it  is  recalled  that 
the  Bessemer  process  was  made  a  commercial  success  only  through  deoxi- 
dizing with  manganese.  This  element,  then,  plays  a  very  vital  part,  the 
effect  in  the  product  most  evident  being  the  prevention  of  that  combination 
of  hot  and  cold  shortness  commonly  spoken  of  as  rottenness.  It  is  due  to 
the  presence  in  the  metal  of  iron  oxide,  FeO,  which  is  dissolved  by  molten 
iron.  This  oxide  is  reduced  by  metallic  manganese,  thus :  (a)  FeO+Mn= 
MnO+Fe.  As  MnO  is  not  soluble  in  iron  to  any  appreciable  extent,  reaction 
(a)  will  result  in  ridding  the  steel  of  all  but  traces  of  metallic  oxide.  Carbon 
may  act  as  a  deoxidizer,  according  to  some  authorities,  as  shown  by 
reaction  (b). 

(b)     FeO+C=Fe+CO. 

However,  the  evolution  of  CO  gas  that  produces  the  violent  boiling  of  the 
metal  in  the  ladle,  which  boiling  often  continues  also  in  the  ingot  mould  after 
the  metal  has  been  teemed,  is  probably  caused  by  CO  and  other  gases  passing 
out  of  solution  in  the  metal  as  the  latter  cools.  Small  amounts  of  these  gases 
retained  by  the  steel  produce  the  blow  holes  previously  alluded  to.  It  is 


CHEMISTRY  OF  THE  PROCESS  197 

to  be  noted,  also,  that  manganese  offsets  the  evil  effects  of  sulphur  as  will 
be  explained  in  a  later  chapter.  The  silicon  as  well  as  the  carbon  and 
manganese  in  the  ferro  or  spiegel  and  pig  iron  will  also  serve  as  a  deoxidiz- 
ing agent.  Besides,  silicon,  by  attacking  CO,  prevents  the  formation  of 
blow  holes.  For  the  greatest  effectiveness  a  considerable  excess  of  silicon 
and  manganese  over  that  required  by  their  respective  reactions  should 
be  used.  This  is  one  of  the  reasons  why  the  manganese  in  steel  will  range 
from  .30  to  1.00%.  Additional  losses  of  the  manganese  in  the  recarburizer 
are  likely  to  occur  by  reacting  with  the  silicate  of  iron  oxide,  thus: 

(c)  FeO  'SiO2+Mn=MnO  *SiO2+Fe. 

A  study  of  Bessemer  slags  shows  that  a  slight  decrease  of  iron  oxide  without 
a  corresponding  increase  of  MnO  takes  place  on  recarburizing.  This  cir- 
cumstance is  usually  explained  by  assuming  that  one  of  the  following 
reactions  takes  place: 

(d)  FeO+C=Fe+CO    or 

(e)  ,2FeOSiO2+CO=FeO  •  (SiO2)2+CO2+Fe. 

As  was  pointed  out  under  the  head  of  teeming,  other  deoxidizing  agents 
may  be  added  to  the  ingot  as  the  metal  is  being  teemed.  The  one  most 
commonly  employed  is  aluminum.  This  element  is  one  of  the  most  powerful 
deoxidizers  known.  Upon  being  heated  to  a  sufficiently  high  temperature 
it  will  react  violently  with  all  the  metallic  oxides,  and  also  many  others. 

(f)  3  FeO+2Al=Al2O3+3Fe. 

Various  alloys  are  beginning  to  be  used  for  this  purpose,  also.  One  of 
the  best  is  known  as  "A.  M.  S."  metal;  it  is  an  alloy  of  aluminum,  man- 
ganese and  silicon,  and  is  said  to  be  very  efficient  for  this  purpose. 


198  THE  OPEN  HEARTH  PROCESS 


CHAPTER  VIII. 

THE  BASIC  OPEN  HEARTH  PROCESS. 

SECTION   I. 

SOME    GENERAL  FEATURES   OF   THE    SIEMENS   PROCESS. 

Early  History  of  the  Process:  The  ever  increasing  demand  for  steel, 
which  even  the  phenomenal  success  of  Bessemer  was  not  able  to  meet 
entirely,  soon  led  many  other  inventors  into  the  same  field.  But  the  only 
process  which  was  destined  to  become  a  rival  of  the  Bessemer  was  developed 
through  the  invention  of  the  regenerative  principle  by  that  prolific  inventor, 
William  Siemens.  In  this  connection  it  may  be  of  interest  to  note  that 
Siemens  first  developed  and  employed  this  principle  in  the  construction  of 
steam  engines,  but  while  several  of  these  engines  were  built  and  put  into 
use,  they  were  finally  abandoned  because  of  the  severe  wear  on  the  heating 
chambers  caused  by  the  high  temperature  attainable.  But  it  was  shown 
that  a  great  saving  of  fuel  and  very  high  temperatures  could  be  obtained 
by  the  use  of  the  principle,  and  at  the  suggestion  of  his  brother,  Frederick, 
Siemens  then  turned  his  attention  to  the  application  of  the  principle  for 
producing  high  temperatures  in  furnaces.  The  first  experimental  furnace 
was  built  in  1858,  when  it  was  developed  that,  with  large  furnaces  especially, 
many  difficulties  were  to  be  overcome,  if  the  full  efficiency  which  the  use 
of  the  principle  promised  was  to  be  obtained.  After  two  years  or  more 
of  experimentation,  Siemens  fell  upon  the  plan  of  gasifying  the  fuel  prior 
to  burning  it  in  the  furnace,  when  he  found  that  most  of  his  difficulties 
had  been  overcome.  The  first  furnace  burning  gaseous  fuel,  patented  in 
1861,  was  used  for  making  glass.  Here,  the  great  advantages  of  the  furnace 
in  economy  and  regularity  of  working  were  fully  proven,  and  it  was  not 
long  until  it  was  adopted  in  other  industries,  also.  Some  of  these  early 
uses  of  the  furnace  were  for  zinc  distillation,  for  puddling,  for  reheating 
iron  and  steel,  and  for  melting  crucible  steel.  Siemens  then  turned  his 
attention  to  the  manufacture  of  steel  in  his  furnace,  and,  though  many  trials 
were  made  at  many  different  works,  he  met  with  only  indifferent  success. 
Finally,  like  Bessemer,  he  found  it  necessary  to  erect  a  steel  works  of  his 
own  in  which  the  success  of  the  process  could  be  demonstrated.  These 
works  were  located  at  Birmingham,  England,  and  were  at  first  employed 
in  a  remelting  process  by  which  steel  of  the  best  quality  was  obtained 
from  such  scrap  as  old  iron  rails,  plates,  etc.  In  the  meantime,  Siemens 
was  busy  developing  an  idea  of  decarbonizing  pig  iron  for  making  steel  by 
means  of  iron  ore,  and  by  the  year  1868  he  had  proved  that  this  process 
could  be  successfully  employed.  Siemens  next  turned  his  attention  to 


PRINCIPLES  199 


evolving  a  method  whereby  steel  could  be  produced  directly  from  the  ore, 
thus  dispensing  with  the  blast  furnace.  In  this  feat  he  actually  succeeded, 
but  the  cost  of  production  was  many  times  that  of  producing  steel  from 
pig  iron.  Nevertheless,  he  continued  his  experiments  until  his  untimely 
death  in  1883  put  an  end  to  his  endeavors.  He  died  firmly  believing  that 
his  direct  process  would  eventually  supplant  all  conversion  methods.  Sub- 
sequent endeavors  have  shown  this  idea  is  wrong,  and  that  his  pig  and  ore 
process  is  the  most  practicable  and  economical. 

Principles  of  Siemens  Pig  and  Ore  Process:  Briefly,  the  method  of 
Siemens  was  as  follows:  He  used  a  rectangular  covered  furnace  to  contain 
the  charge  of  pig  iron  or  pig  iron  and  scrap,  and  provided  most  of  the  heat 
for  the  chemical  reactions  by  passing  burning  gas  over  the  top  of  the 
materials.  The  gas,  with  a  quantity  of  air  more  than  sufficient  to  burn 
it,  was  introduced  through  ports  at  each  end  of  the  furnace,  alternately 
at  one  end  and  the  other.  The  gaseous  products  of  combustion  passed  out 
of  the  port,  temporarily  not  used  for  entrance  of  gas,  into  chambers  partly 
filled  with  checker  brick,  which  absorbed  some  of  their  sensible  heat,  and 
from  these  chambers  out  through  a  stack.  After  a  short  time,  the  gas  and 
air  were  shut  off  at  the  one  end  and  introduced  through  the  heated  checker 
chambers  at  the  opposite  end,  absorbing  some  of  the  heat  stored  in  the 
bricks.  These  gases  then  entered  the  furnace  with  a  high  sensible  heat 
and  gave  a  higher  temperature  in  combustion  than  could  be  obtained 
without  preheating.  In  about  twenty  minutes,  the  course  of  the  gas  and 
air  was  reversed,  so  that  they  entered  through  the  port  first  used;  and 
a  series  of  such  reversals,  occurring  every  fifteen  to  twenty  minutes,  was 
continued  until  the  oxidation  had  reached  the  desired  point.  The  elements 
in  the  iron  attacked  by  the  oxygen  of  the  air  and  of  the  iron  ore  fed  in  were 
carbon,  silicon  and  manganese,  all  three  of  which  could  be  reduced  to  as 
low  a  limit  as  in  the  Bessemer  process.  Thus,  as  in  all  the  other 
processes  for  purifying  pig  iron,  the  basic  principle  of  Siemens  process  was 
that  of  oxidation.  But  in  other  respects  it  was  unlike  any  other  process. 
True,  it  resembled  the  puddling  process  in  both  the  method  and  the 
agencies  employed,  but  the  high  temperature  attainable  in  his  furnace 
permitted  him  to  secure  in  the  liquid  state  a  perfectly  malleable  metal 
which  could  be  cast  into  ingots  and  be  free  of  slag.  In  this  respect  the 
same  result  was  produced  as  in  the  Bessemer  process,  but  by  a  different 
method  and  through  different  agencies,  both  of  which  imparted  to  it  many 
advantages  over  the  older  pneumatic  process. 

Advantages  of  the  Process:  These  advantages  may  be  briefly 
summed  up  as  follows:  1.  By  the  use  of  ore  as  an  oxidizing  agent  and  by 
the  external  application  of  heat,  the  temperature  of  the  bath  is  made 
independent  of  the  purifying  reactions,  and  the  elimination  of  the  impurities 
can  be  made  to  take  place  gradually,  so  that  both  the  temperature  and 
the  composition  of  the  bath  are  under  much  better  control  than  in  the 


200  OPEN  HEARTH  PROCESS 

Bessemer  process.  2.  For  the  same  reasons,  a  greater  variety  of  raw 
materials  can  be  used  and  a  greater  variety  of  products  can  be  produced 
by  this  than  by  the  Bessemer  process.  3.  A  very  important  advantage 
is  due  to  the  increased  output  of  finished  steel  from  the  same  amount  of 
pig  iron,  which  means  that  fewer  blast  furnaces  are  required  to  produce 
a  given  tonnage  of  steel.  4.  Finally,  with  the  development  of  the  basic 
process,  the  greatest  advantage  of  the  Siemens  over  the  Bessemer  was 
revealed  through  the  elimination  of  phosphorus.  Comparing  the  basic 
open  hearth  with  the  Thomas-Gilchrist  process  it  is  to  be  noted  that, 
due  to  the  different  temperature  conditions,  phosphorus  is  eliminated  in 
the  former  before  the  carbon,  whereas  it  is  not  oxidized  in  the  latter  process 
until  after  the  carbon,  in  what  is  known  as  the  after-blow.  Hence,  while 
the  basic  Bessemer  process  requires  a  pig  iron  with  a  phosphorus  content 
of  2.00%  or  more  in  order  to  maintain  the  temperature  high  enough  for 
the  after-blow,  the  basic  open  hearth  permits  the  use  of  iron  of  any  phos- 
phorus content.  In  the  United  States  this  fact  is  of  the  greatest  importance, 
since,  for  reasons  already  explained,  it  makes  available  immense  ore  deposits 
which  could  not  otherwise  be  utilized.  For  this  reason  the  basic  open 
hearth  process  has  become  the  leading  method  in  this  country. 

Mechanical  Changes  and  Improvements  in  Siemens  Process:     As 

would  be  expected,  many  variations  of  the  process,  both  mechanical  and 
metallurgical,  have  been  worked  out  since  Siemens  first  put  his  method 
into  operation.  Along  mechanical  lines  various  improvements  in  the 
design,  the  size  and  the  arrangement  of  the  parts  of  the  furnace  have  been 
made.  Originally,  the  furnace  had  a  capacity  of  only  four  or  five  tons, 
but  now  the  size  ranges  from  40  to  100  tons  capacity,  and  in  new  plants 
the  capacity  will  seldom  be  less  than  75  tons.  But  the  greatest  departure 
from  Siemens'  original  plan  was  made  by  the  invention  of  the  tilting  or 
rolling  furnace.  These  furnaces  are  of  two  types,  and  are  known  as  the 
Campbell  and  the  Wellman  furnaces,  respectively.  In  each  case  the 
furnace  is  built  of  brick,  which  are  held  firmly  in  piace  by  a  strong  frame- 
work of  steel,  and  is  mounted  upon  rollers  or  rockers,  thus  permitting  it 
to  be  tilted  either  forward  or  backward.  In  the  Wellman  type  the  hearth 
and  ports  are  built  solid,  so  that  both  move  together;  and  as  tilting  the 
furnace  breaks  the  connections  with  the  regenerator  flues,  the  furnace  can 
be  fired  only  when  in  an  upright  position.  This  fault  is  overcome  in  Camp- 
bell's invention,  in  which  the  hearth  only  is  movable,  and  the  center  of 
rotation  is  coincident  with  the  center  line  of  the  ports.  By  the  use  of 
water  cooled  castings,  fairly  tight  joints  are  made  between  the  hearth  and 
the  flues,  so  that  the  furnace  may  be  tilted  in  either  direction,  forward  or 
backward,  without  turning  off  the  gas  and  air. 

Metallurgical  Improvements:  The  hearth  of  Siemens'  furnace  was 
of  acid  brick  construction,  and  the  bottom  was  made  up  of  sand — essentially 
as  in  the  acid  process  of  today.  Later  on,  in  order  to  permit  the  charging 


IMPROVEMENTS  201 


of  limestone  for  the  removal  of  phosphorus,  the  hearth  was  constructed 
with  a  lining  of  magnesite  brick,  which  were  covered  with  a  layer  of  burned 
dolomite  or  magnesite  to  replace  the  sand  of  the  acid  furnace.  These 
furnaces  were,  therefore,  designated  as  basic  furnaces.  The  pig  and  scrap 
process  was  originated  by  the  Martin  Brothers.  By  substituting  scrap 
for  the  ore  in  Siemens'  pig  and  ore  process  they  found  it  was  possible  so 
to  dilute  the  charge  with  steel  scrap  that  little  oxidation  was  necessary. 
Since  the  time  of  the  Martins,  these  processes  have  undergone  various 
modifications,  chief  of  which  are  those  known  as  the  Talbot,  the  Campbell, 
the  Bertrand-Thiel,  and  the  Monell  processes.  By  using  a  basic  lined 
tilting  furnace  in  which  a  large  bath  of  the  purified  molten  metal  is  always 
retained,  Talbot  succeeded  in  hastening  the  oxidation  of  the  silicon,  manga- 
nese, phosphorus  and  carbon  to  such  an  extent  that  the  operation  is  made 
more  nearly  continuous,  and  the  time  between  heats  or  tappings  is  greatly 
reduced.  Campbell's  tilting  furnace  permits  him  to  apply  the  pig-and-ore 
process  to  molten  metal,  because,  by  tilting  the  furnace  forward,  the  frothing 
of  the  bath,  produced  by  the  violent  reactions,  is  prevented  from  throwing 
the  slag  through  the  doors  as  would  be  the  case  in  a  stationary  furnace. 
By  a  combination  process,  he  also  aims  to  make  acid  steel  from  basic  pig 
iron.  In  a  basic  lined  furnace  he  eliminates  the  silicon,  manganese,  phos- 
phorus and  a  little  of  the  carbon,  then  pours  this  semi-purified  metal  into 
an  acid  furnace,  where  the  remainder  of  the  carbon  is  worked  down  as  in 
the  regular  acid  process.  The  Bertrand-Thiel  process  is  applied  to  pig 
iron  with  a  very  high  phosphorus  content,  and  makes  use  of  the  two-period 
scheme  of  purification,  also.  In  the  first  period,  the  furnace  is  tapped  in 
order  to  separate  the  metal  from  the  slag,  which  contains  such  a  high 
percentage  of  phosphoric  acid,  P2O5,  that  it  is  valuable  as  a  fertilizer. 
The  metal  is  then  poured  either  back  into  the  same  furnace  or  into  another 
basic  furnace  for  the  final  purification.  -In  developing  his  process,  Monell 
had  the  same  objects  in  mind  as  Talbot,  namely,  the  rapid  conversion  of 
basic  iron  into  steel;  but  he  wished  to  avoid  the  reservoir  of  molten  metal, 
and  make  his  process  adaptable  to  the  stationary  furnace.  He  accom- 
plished his  object  by  first  charging  limestone  and  ore  into  a  basic  furnace, 
heating  these  until  the  batch  became  pasty,  then  adding  molten  pig  iron, 
when  the  silicon,  manganese,  and  phosphorus  were  rapidly  oxidized  and,  with 
the  lime,  formed  a  slag  that,  as  the  carbon  began  to  be  oxidized,  foamed 
up  and  ran  from  the  furnace  through  slag  notches  provided  for  the  purpose. 

The  Process  for  the  Pittsburgh  District:  Most  of  the  pig  iron 
available  in  the  Pittsburgh  district  contains  a  fairly  high  percentage  of 
phosphorus,  and  the  mills  produce  considerable  scrap.  Hence,  the  furnaces 
are  practically  all  basic — the  Carnegie  Steel  Company  no  longer  operates 
any  acid  open  hearth  furnaces — and  a  combination  of  the  pig-and-ore,  pig-and- 
scrap,  and  Monell  processes  is  employed.  It  has  been  briefly  described  as 
follows:  Limestone  is  charged  on  a  basic  bottom,  ore  is  charged  on  top 
of  the  stone,  and  scrap  on  top  of  this;  if  molten  pig  iron  cannot  be  obtained 


202  OPEN  HEARTH  PROCESS 

in  sufficient  quantity  to  complete  the  charge,  some  cold  pig  is  charged 
with  the  scrap;  and  the  entire  mass  is  heated  in  the  furnace  for  about  two 
hours,  or  until  the  scrap  is  white  hot  and  slightly  fused.  Molten  pig  iron 
is  then  added,  when  a  lively  reaction  occurs,  in  which  almost  all  of  the 
silicon,  manganese,  phosphorus  and  part  of  the  carbon  are  oxidized,  the 
first  three  forming  compounds  that  slag  with  the  iron  oxide,  and  join  the 
iron  and  lime  silicates  that  are  already  melted.  About  80%  of  this  slag 
is  drawn  off  by  the  end  of  two  or  three  hours  more.  The  ore  acts  on  the 
carbon  for  three  or  four  hours  longer,  during  which  time,  and  continuing 
afterwards,  the  limestone  is  being  decomposed  by  the  heat,  and  its  CO2 
is  bubbling  up  through  the  bath  and  exposing  part  of  the  metal  to  the  flame, 
thus  oxidizing  it  and  completing  the  purification  started'by  the  ore  reaction. 
What  is  known  as  the  lime  action,  or  boil,  lasts  two  or  three  hours  longer; 
and  then,  if  the  charge  was  calculated  correctly,  the  carbon  content  will 
be  somewhat  greater  than  that  at  which  the  metal  is  to  be  tapped. 
Ordinarily,  of  course,  the  carbon  is  too  low  or  too  high,  in  which  cases 
more  pig  or  more  ore  must  be  added.  In  about  another  hour  the  carbon 
content  will  have  been  reduced  to  the  proper  amount  for  tapping,  which  is 
usually  about  .10%. 

SECTION   II. 

EQUIPMENT  FOR  A   MODERN   BASIC  OPEN  HEARTH   PLANT. 

The  Modern  Plant:  Besides  the  furnaces  themselves,  the  modern 
open  hearth  plant  requires  considerable  additional  equipment.  Thus,  there 
must  be  provided  ladles  for  containing  molten  metal;  moulds  for  ingots; 
cranes  and  charging  machines  for  handling  materials;  boxes  for  the  solid 
materials;  dinkeys  or  electric-engines  for  hauling  the  materials;  a  stripper 
for  removing  the  moulds  from  the  ingots;  a  great  number  of  small  articles, 
like  shovels,  wheel  barrows,  rabbles,  etc.;  and,  finally,  apparatus  for  pre- 
paring or  controlling  the  fuel  supply.  In  addition  the  more  modern  plants 
will  be  provided  with  a  mixer,  a  calcining  plant,  and  also  spiegel-cupolas, 
if  liquid  recarburizers  are  used.  A  brief  description  of  the  more  essential 
items  enumerated  above  is  given  herewith. 

Calcining  Plant:  At  most  of  the  plants  there  are  cupolas  for  roasting 
dolomite.  These  furnaces  are  cylindrical  in  form,  and  each  one  is  so  placed 
that  one  base  forms  the  bottom,  the  other  the  open  top  of  the  furnace. 
In  the  usual  construction  the  cupola  is  made  up  of  an  outer  shell  of  boiler 
pi  ate,  one-half  inch  thick,  and  a  double  refractory  lining  made  of  two  courses 
of  brick,  the  inner  one  being  of  first  quality  and  the  outer  one  next  to  the. 
shell  of  second  quality  fire  brick.  On  the  floor  of  the  furnace,  there  is  a 
cone  shaped  casting  which  deflects  the  burnt  dolomite,  in  its  descent, 
toward  the  circumference,  where  it  may  pass  out  through  openings  provided 
for  the  purpose  in  the  base  of  the  cupola.  For  fuel,  coke  is  employed,  and 
it  must  be  burned  by  an  air  blast.  This  blast  is  supplied  at  a  pressure 


PLANT  EQUIPMENT  203 


of  five  to  six  ounces.  A  bustle  pipe  distributes  the  air  and  is  provided  with 
about  eight  tuyeres,  or  connections,  with  the  cupola.  Built  on  the  charging 
platform  and  extending  about  three  feet  above  it,  there  is  a  seat  upon  which 
the  charging  bucket  is  deposited  by  a  crane  and  from  which  its  contents, 
through  a  bell  and  hopper  arrangement  in  the  bottom  of  the  bucket,  may 
be  dropped  into  the  cupola.  Usually  the  ratio  of  materials  in  the  charge  is 
two  buckets  of  dolomite  to  one  bucket  of  coke.  Thus,  the  fuel  consumption 
is  about  15%  of  the  weight  of  dolomite  calcined.  The  operation  of  burning, 
in  which  the  CC>2  is  expelled  from  the  stone,  leaving  calcium  and  magnesium 
oxides  (CaO  and  MgO)  in  place  of  their  carbonates  (CaCO3  and  MgCOa), 
requires  from  ten  to  twelve  hours.  The  burning  period  is  controlled  by  the 
rate  at  which  this  material  is  withdrawn.  As  fast  as  the  dolomite  is 
burned  it  is  shoveled  out  at  the  bottom,  crushed  to  pass  a  half-inch  mesh, 
then  conveyed  to  the  loading  bins,  whence  it  is  later  taken  as  required 
to  the  open  hearth. 

Fuels:  For  fuels  in  open  hearths,  natural  gas,  coke  oven  gas,  producer 
gas,  powdered  coal,  fuel  oil  and,  sometimes,  tar  are  used.  The  choice  of 
fuel  depends  largely  upon  the  location  of  the  plant.  Natural  gas  is,  of 
course,  preferable  when  it  can  be  obtained,  as  it  is  of  uniform  composition, 
is  easily  controlled  and  imparts  no  sulphur  to  the  bath,  while  coke  oven  gas, 
producer  gas  and  powered  coal  are  of  varying  composition  and  quality  and  may 
impart  some  sulphur  to  the  bath.  The  great  demand  for  petroleum  pro- 
ducts has  made  fuel  oil  too  costly,  while  the  supply  of  tar  is  so  limited  that 
it  is  not  always  available  as  an  open  hearth  fuel.  There  remains,  then,  as 
the  principle  substitutes  for  natural  gas,  only  powdered  coal,  coke  oven  gas 
and  producer  gas,  all  of  which  have  already  been  discussed  in  the  chapter  on 
fuels.  (See  Chapter  IV.,  Section  6).  In  either  case,  coal  of  the  best  grade 
obtainable  is  desired,  especially  with  respect  to  sulphur,  as  there  is  always 
danger  of  its  being  absorbed  by  the  bath.  In  using  coke  oven  gas  from 
which  the  benzol  has  been  removed,  it  is  found  necessary  to  burn  with  it  some 
substance  like  tar,  for  example,  that  will  impart  luminosity  to  the  flame,  as 
otherwise  the  poor  visibility  within  the  furnace  makes  it  difficult  for  the 
melter  to  control  the  temperature.  In  the  new  plants  of  the  Carnegie  Steel 
Company,  the  producers  are  connected  in  sets  of  four — five  in  one  or  two 
cases — •  and  each  set  serves  two  furnaces,  the  gas  mains  from  the  producers 
being  arranged  so  that  any  one  or  all  of  the  producers  in  a  set  may  discharge 
into  either  one  or  both  of  the  furnaces. 

Fuel  Consumption:  It  is  a  difficult  matter  to  arrive  at  any  conclusion 
as  to  the  amount  of  heat  required  to  produce  a  ton  of  steel.  It  is  subject  to 
a  number  of  conditions  such  as  kind  of  fuel  used,  condition  of  the  furnace 
and  checkers,  continuity  and  rate  of  production,  and  the  care  and  intelligence 
with  which  the  furnace  is  operated.  In  actual  practice  the  number  of  heat 
units  per  ton  of  steel  produced  is  found  to  vary  from  5,000,000  B.  t.  u.  to  6,000,000 
B.  t.  u.  when  natural  gas  is  used,  and  from  6,000,000  B.t.u.  to  8,500,000  B.t.u. 
when  other  fuels  are  employed.  An  inspection  of  the  fuel  records  of  several 


204  OPEN  HEARTH  PROCESS 

different  plants  and  a  consideration  of  averages  for  long  periods  of  time,  vary- 
ing from  six  months  to  a  year,  indicate  that  the  fuel  consumption  per  gross 
ton  of  steel  produced,  to  be  considered  good  practice,  should  be  about  as  follows: 
natural  gas,  5,000  cubic  feet;  coke  oven  gas, 8, 000  cubic  feet, with  16  gallons  of  tar; 
tar  alone,  45  gallons;  producer  gas  equivalent  to  600  pounds  of  coal ;  and  powered 
coal,  500  pounds. 

Hot  Metal  Mixer:  The  advantages  of  the  hot  metal  mixer  have 
already  been  discussed  in  connection  with  the  Bessemer  process;  and 
although  the  conditions  in  the  open  hearth  plant,  where  large  quantities 
of  metal  are  needed  at  irregular  and  uncertain  intervals  of  time,  are  exactly 
the  reverse  of  those  in  a  Bessemer  plant,  which  requires  small  quantities 
of  metal  at  short  and  comparatively  regular  intervals,  these  advantages 
are  as  applicable  to  the  one  case  as  to  the  other.  In  order  that  these 
advantages  may  be  realized  to  the  fullest,  open  hearth  mixers  should  have 
a  large  capacity.  One  large  mixer  of  1000  or  1200  tons  capacity  is  to  be 
preferred  to  two  of  500  tons  capacity. 

Spiegel  Cupolas:  In  plants  manufacturing  large  quantities  of  medium 
high  carbon,  high  manganese  steels,  such  as  is  used  for  railroad  rails,  for 
example,  the  use  of  spiegel  for  recarburizing  may  be  advantageous,  in  which 
case  cupolas  for  melting  the  spiegel  mixtures  are  an  important  adjunct 
to  the  open  hearth  plant.  In  construction  and  operation,  these  cupolas 
are  similar  to  those  already  described  for  the  Bessemer  plant.  For  collect- 
ing and  weighing  the  different  ingredients  of  the  charge,  a  larry  car  equipped 
with  a  multiple  beam  scale  is  most  convenient.  In  charging,  the  metallic 
parts  of  the  burden,  consisting  usually  of  spiegel  and  pig  iron,  are 
charged  into  the  cupola  together,  while  the  coke,  with  which  is  mixed 
enough  limestone  to  flux  its  ash,  is  charged  separately.  The  proportion 
of  coke  required  in  each  round  will  vary  somewhat,  but  in  good  practice  it 
will  seldom  exceed  seven  per  cent,  of  the  weight  of  the  metallic  part  of  the 
charge.  To  secure  greater  uniformity  and  provide  an  ever-ready  supply  of 
molten  recarburizer,  the  cupolas  attached  to  the  most  modern  plants  are 
provided  with  a  small  mixer.  By  means  of  brick  and  clay  lined  runners  the 
metal  from  the  tap  hole  of  each  cupola  is  conducted  directly  into  this  mixer, 
from  which  definite  amounts  may  be  taken  as  desired.  For  weighing  the 
recarburizing  metal,  a  track  scale,  on  which  the  transfer  ladle  may  rest 
during  the  pouring,  is  placed  on  the  track  directly  in  front  of  the  mixer. 
The  manganese  content  of  the  molten  recarburizer  is  varied  to  suit  the 
requirements  of  the  different  grades  of  steel  by  varying  the  amount  of 
pig  iron  with  which  the  standard  spiegel  is  diluted.  Varying  the  proportion 
of  pig  iron  to  spiegel  also  changes  the  carbon  content  of  the  mixture  slightly. 
With  a  given  weight  of  standard  spiegel,  the  more  pig  iron  charged  the  lower 
the  carbon  content  of  the  mixture  will  be,  as  can  readily  be  seen  by 
comparing  the  analyses  of  these  materials. 

The  Steel  Ladles:  The  ladle  for  receiving  the  steel  is  made  of  boiler 
plate  and  is  lined  with  two  courses  of  brick  each  2y2  inches  thick.  The  first 
layer,  next  to  the  shell,  is  usually  of  fire  brick,  while  the  second  layer  is  of 


PLANT  EQUIPMENT  205 

white  river  brick.  Both  courses  are  laid  on  end  in  a  motar  of  fire  clay,  to 
which  a  little  loam  is  sometimes  added.  The  capacity  of  the  vessel  is  depen- 
dent on  the  amount  of  steel  to  be  handled  in  each  heat,  which  in  turn  is  fixed 
by  the  capacity  of  the  open  hearth.  The  opening  at  the  bottom  of  the  ladle 
is  provided  with  a  fireclay  nozzle  about  two  inches  in  diameter,  which  may 
be  closed  by  a  stopper.  The  stopper  is  made  of  [clay  bonded  graphite  and 
is  mounted  on  a  rod,  protected  by  fireclay  sleeve  brick,  that  reaches  to  the 
top  of  the  ladle;  there  it  is  connected  to  a  sliding  bar  on  the  outside  that  can 
be  raised  or  lowered  by  a  lever  near  the  base.  Both  the  stopper  and  the 
nozzle  must  be  replaced  after  each  heat.  Great  care  is  necessary  both  in 
placing  the  nozzle  and  in  setting  the  stopper  in  the  nozzle,  for  a  bad  fit 
results  in  a  running  stopper,  which  may  cause  a  great  waste  of  metal.  To 
prevent  the  steel  from  chilling  about  the  stopper,  powdered  coal  is  often 
thrown  into  the  depression  around  the  nozzle  just  before  tapping  a  heat. 

The  Stripper:  The  action  of  this  machine  has  already  been  described 
in  connection  with  the  Bessemer  process.  The  ingots  must  all  be  sufficiently 
cooled  before  stripping,  so' that  there  will  be  no  danger  of  breaking  the 
solidified  wall  of  metal.  After  being  stripped,  the  ingots  are  then  ready  to  be 
sent  to  the  soaking  pits  previous  to  the  rolling.  To  strip  an  ingot,  it  is  only 
necessary,  in  the  majority  of  cases,  to  place  the  jaws  of  the  stripping  machine 
under  the  lugs  on  the  mould  and  apply  the  lifting  force,  when  the '  mould 
will  slip  from  the  ingot  and  can  then  be  raised  to  a  sufficient  height  to 
transfer.  It  is  only  at  times,  usually  due  to  a  defective  mould  or  to 
metal  being  splashed  over  the  top  edges  from  a  running  stopper,  that  the 
moulds  are  not  slipped  off  easily,  and  then  the  plunger  is  rested  on  top  of 
the  ingot  as  the  mould  is  drawn  upward.  When  this  treatment  fails  to 
loosen  an  ingot,  it  is  sent  to  the  mould  yard  where  more  time  is  available 
for  extracting  it  and  where  it  may  be  subjected  to  various  treatments 
according  to  the  means  at  hand  and  the  cause  of  its  sticking. 

Moulds:  After  the  ingots  of  each  heat  are  stripped  the  empty  moulds 
are  stored  in  the  mould  yard  until  they  are  sufficiently  cool  to  be  drawn  back 
to  the  open  hearth  for  another  charge,  and  during  the  wait  they  are  washed 
inside  with  clay  slurry,  the  water  of  which  is  quickly  evaporated  by  the 
heat  of  the  mould,  leaving  it  covered  with  a  thin  coating  of  the  clay.  Any 
damaged  moulds  that  cannot  be  used  are  charged  as  cold  iron,  as  they  are 
cast  from  a  good  grade  of  Bessemer  pig  iron.  Many  types  and  sizes  of 
moulds  are  used.  Heavy  moulds  chill  the  surface  of  the  steel  quickly 
and  hasten  the  solidification,  which  always  proceeds  from  the  wall  of  the 
mould  toward  the  middle  of  the  ingot.  Since  steel  contracts  on  solidifying, 
there  is  a  cavity  left  directly  under  the  top  surface  of  the  ingot,  as  the 
metal  in  this  location  is  the  last  to  solidify.  This  cavity,  called  the  pipe, 
is  responsible  for  the  production  of  a  great  deal  of  scrap  in  rolling  the  steel. 
There  are  numerous  methods  to  reduce  the  size  of  the  pipe  and  to  keep  it 
as  near  the  top  as  possible,  but  it  cannot  be  entirely  eliminated.  The 
principle  of  most  of  the  devices  is  to  keep  the  top  of  the  ingot  molten  longer 


206  OPEN  HEARTH  PROCESS 

than  the  bottom,  so  that  the  molten  steel  on  top  will  flow  into  the  cavity 
as  fast  as  it  forms  and  thus  lessen  the  extent  of  the  pipe.  The  Gathman  type 
of  mould  depends  upon  uneven  thickness  of  mould  wall  to  effect  the  same 
result.  By  having  the  mould  thin  at  the  top  and  thick  at  the  bottom, 
the  thin  top  has  a  less  chilling  effect  on  the  molten  steel  at  the  top, 
which,  therefore,  is  the  last  to  solidify.  A  similar  method  consists  in 
lining  a  removable  top  of  the  mould  with  brick  or  clay,  thus  preventing 
rapid  conduction  and  radiation.  Some  try  to  keep  the  steel  at  the  top  of  the 
ingot  fluid  by  a  coke,  a  charcoal  or  a  gas  fire.  Many  other  more  complicated 
devices  have  been  invented,  also,  but  their  use  involves  much  additional 
expense.  Besides,  piping  is  regarded  by  many  as  a  necessary  evil,  and  the 
safest  way  to  avoid  it  is  to  allow  a  proper  discard  from  the  top  of  the  ingot, 
which  discard  is  cut  off  at  the  blooming  mill  shears.  Armor  plate  ingots 
are  sometimes  cast  in  specially  constructed  hard  sand  moulds.  Ingots 
for  this  material  are  always  bottom  cast,  two  ladles  being  poured  at  the 
same  time,  which  are  followed  frequently  by  a  third,  pouring  directly  into 
the  mould.  There  are  standard  sinkheads  for  all  armor  plate  ingots. 

The  Charging  Machine:  Of  all  the  labor  saving  devices  employed 
about  the  open  hearth  plant,  none  have  brought  a  greater  saving  of  money 
and  time  than  the  charging  machine.  Indeed,  it  may  be  looked  upon  as  the 
most  essential  part  of  the  equipment,  for  if  the  charging  were  done  by  hand, 
the  time  thus  lost,  especially  in  the  case  of  the  large  furnaces,  would  be 
so  great  that  this  feature  would  appear  as  a  serious  drawback  to  the  process. 
There  are  several  types  of  these  machines,  but  the  ones  most  generally 
employed  are  of  the  low  ground  type.  They  consist  of  two  main  parts. 
First,  there  is  the  bottom  truck  made  up  of  a  very  strong  steel  frame-work 
and  mounted  on  flanged  wheels  which  travel  on  a  very  wide  gage  track 
laid  in  front  of  the  furnace.  Next,  there  is  the  charging  carriage,  which 
moves  over  a  track,  laid  on  the  frame  of  the  truck,  at  right  angles  to  the 
direction  of  motion  of  the  truck  itself.  On  this  carriage  is  mounted  a 
kind  of  lever,  the  long  arm  of  which  extends  toward  the  furnace  and  is 
known  as  the  charging  bar.  The  charging  bar  is  hollow  to  provide  space 
and  bearings  for  the  locking  bar,  about  which  it  can  be  made  to  revolve, 
and  is  shaped  on  the  end  to  fit  into  the  socket  of  the  charging  box.  The 
charging  bar  is  thus  capable  of  giving  eight  different  primary  motions, 
or  any  number  of  resultants  of  these  motions.  In  operating  the  machine, 
the  charging  boxes  rest  on  buggies  running  on  a  narrow  gage  track  between 
the  machine  and  the  furnace.  First,  the  truck  of  the  machine  is  moved 
so  that  the  charging  bar  is  directly  opposite  the  charging  box  to  be  emptied, 
then  the  carriage  is  moved  forward  to  bring  into  position  the  end  of  the 
charging  bar,  which  is  then  dropped  ( into  the  socket  on  the  end  of  the 
charging  box  and  locked  in  position  by  advancing  the  locking  bar  until  its 
front  end  projects  into  a  hole  provided  for  the  purpose  in  the  socket  of  the 
box.-  Now,  the  machine  is  made  to  serve  for  a  shifting  engine,  and,  by 
moving  the  truck,  the  whole  train  of  charging  boxes  may  be  moved  along 
in  front  of  the  furnace,  so  that  the  box  engaged  is  brought  directly  opposite 


PLANT  EQUIPMENT  207 

the  door.  The  charging  bar  is  then  raised,  carrying  the  box  with  it,  and 
by  a  forward  motion  of  the  carriage  the  box  is  passed  into  the  furnace, 
where,  by  rotating  the  charging  bar,  the  box  is  turned  upside  down  and 
its  contents  deposited.  By  reversing  these  motions  the  box  is  then  placed 
upon  the  buggy  again.  The  charger  will  pick  up  and  empty  a  box  in  less 
than  a  minute.  As  the  capacity  of  the  box  is  more  than  one  ton,  for  even 
the  lightest  materials  of  the  charge,  it  is  possible  to  charge  even  the  very 
large  furnaces  in  less  than  an  hour.  Charging  machines  are  always  elec- 
trically operated. 

Charging  Boxes :  The  charging  boxes  are  made  of  cast  steel  or  of  five- 
eighth  inch  boiler  plate  with  cast  steel  ends.  One  end  of  the  box  is  provided 
with  a  socket  opening  from  the  top  so  that  the  T  section  on  the  end  of  the 
charging  machine  peel,  or  arm,  may  readily  be  inserted  and  withdrawn  from  it. 
The  boxes  have  a  capacity  of  sixteen  cubic  feet  or  more,  and  into  them  all 
solid  material  for  the  furnace  charge  is  placed.  For  transporting  the  boxes 
from  place  to  place  about  the  works,  buggies  are  provided.  These  buggies 
are  of  standard  or  narrow  gage  type,  are  made  of  cast  iron  and  accom- 
modate three  to  four  boxes  each. 

Stock  Yard :  There  is  usually  one  stock  yard  to  each  plant.  In  it  are 
kept  the  stores  of  limestone,  ore,  cold  pig  and,  sometimes,  scrap,  from 
which  materials  the  cold  charges  for  the  furnaces  are  made  up.  The  ore 
and  limestone  are  loaded  into  the  boxes  from  chutes  or  by  grab  buckets, 
depending  upon  the  manner  of  storing;  the  cold  pig  from  railroad  cars  or 
from  a  stock  pile  by  means  of  a  magnet;  while  the  scrap  is  brought  from 
the  rolling  mills  ready  loaded  in  the  charging  boxes,  or  if  it  is  delivered 
in  railroad  cars,  it  is  transferred  to  them  by  magnets.  Soft  ore  is 
generally  used  to  make  up  a  charge  on  account  of  its  lower  cost,  because 
there  is  no  advantage  in  charging  lump  ore  on  the  bottom,  and  it  is  not 
necessary  to  have  as  pure  an  ore  as  is  the  lump  ore.  After  a  charge  is 
made  up,  the  buggies  are  pushed  over  platform  scales  and  weighed  by 
the  weighmaster,  who  records  the  weights  in  a  stock  book.  The  stock- 
yard men  take  into  account  the  amount  of  pig  iron  to  be  used  and,  to  a 
certain  extent,  the  carbon  contents  of  the  scrap  charged  and  add  to  the 
charge  what  ore  they  think  will  be  necessary.  Reports  giving  the 
weights  of  all  materials  are  made  out  in  triplicate,  one  of  which  is  sent 
to  the  melter,  so  that  after  it  reaches  the  furnace  front  the  melter-foreman 
or  his  first  helper  may  vary  the  ore  charge  to  suit  their  plans  or  ideas. 

Arrangement  of  the  Plant:  The  furnaces  of  the  plant  are  always 
enclosed  and  covered  by  an  immense  steel  building,  and  in  the  modern 
plant  the  furnaces  are  arranged  end  to  end  in  a  long  row  along  the  center 
of  this  building.  That  part  of  the  floor  of  the  building  along  the  front, 
or  charging  side,  of  the  furnace  is  called  the  charging  floor.  On  this  floor 
and  next  to  the  furnaces  is  laid  a  narrow  gage  track  on  which  the  solid 
materials  are  conveyed  to  the  furnace  for  charging,  while,  back  of  the  narrow 
gage  track,  there  extends  a  very  wide  gage  track,  with  a  spread  of  about 


208 


OPEN  HEARTH  PROCESS 


THE  OPEN  HEARTH  FURNACE  209 

twenty  feet,  for  the  charging  machines.  The  space  above  this  floor  and 
the  furnaces  is  spanned  by  two  or  more  electric  overhead  cranes.  The 
remaining  floor  space  of  the  building  lying  along  the  tapping  side  of  the 
furnace  is  called  the  pouring  floor,  and  is  also  spanned  by  electric  cranes. 
These  two  floors  may  be  on  the  same  level,  as  in  some  of  the  older  plants; 
but  all  the  new  plants  are  of  the  two=level  type,  that  is,  the  pouring  floor 
lies  some  twelve  to  eighteen  feet  below  the  level  of  the  charging  floor. 
The  pouring  platforms,  six  to  eight  feet  wide  and  about  eight  feet  high, 
are  located  along  the  outer  edge  of  the  pouring  floor.  The  mixer  and 
cupolas  are  often  located  at  one  end  of  the  open  hearth  building,  as  this 
arrangement  permits  the  transfer  of  the  hot  metal  to  be  made  with  the 
cranes.  However,  in  large  plants  this  arrangement  would  be  inconvenient, 
as  it  would  interfere  with  the  work  of  the  cranes,  so  the  hot  metal  is  carried 
to  the  different  furnaces  on  a  track  laid  on  the  charging  floor.  With  this 
arrangement  the  mixer  may  be  located  at  any  convenient  point.  When 
producer  gas  is  used  for  fuel,  the  producer  plant  is  built  back  of  the  open 
hearth  plant,  parallel  to  the  charging  floor.  The  calcining  plant,  stock 
yard,  and  mould  yard  are  located  at  points  as  convenient  to  the  open 
hearth  house  as  possible.  The  stripper  should  be  placed  so  that  the  steel 
is  always  advancing  toward  the  soaking  pits  of  the  blooming  mill,  though 
this  matter  is  but  a  question  of  convenience. 

SECTION   III. 

CHIEF   FEATURES   OF  BASIC  OPEN   HEARTH   CONSTRUCTION. 

Parts  of  the  Open  Hearth  Furnace  and  Their  Arrangement:    An 

open  hearth  furnace  consists  of  the  furnace  proper,  containing  the  covered 
laboratory,  hearth  or  bath,  in  which  the  charge  is  placed;  ports  for  admitting 
the  gas  and  air  over  the  charge;  regenerative  chambers,  containing  checker 
brick  for  storing  up  heat  from  the  products  of  combustion  and  imparting 
it  to  the  cold  gas  and  air;  flues  and  uptakes,  connecting  the  checker  chambers 
with  the  furnace  proper;  slag  pockets,  which  are  located  at  the  base  of  the 
uptakes;  flues,  leading  from  the  air  and  gas  supply  (if  producer  gas  is  used) 
to  the  checker  chambers,  with  connections  to  the  stack;  valves  for  regulating 
the  direction  of  flow  of  gas,  air  and  waste  gases;  and  the  stack  itself.  The 
furnace  proper  is  located  on  the  level  of  the  charging  floor  and  rests  on 
a  concrete  foundation.  The  slag  pockets,  checker  chambers,  flues  and 
valves  are  all  located  in  a  cellar,  on  a  level  about  fifteen  feet  below  the 
charging  floor  in  houses  of  the  one  level  type,  or  on  the  first  floor  level  in 
the  two  level  type.  The  checker  chambers  are  not  located  under  the  furnace 
proper  but  under  the  charging  floor  in  front  of  it,  and  the  stack  is  placed 
a  short  distance  beyond  nearer  the  gas  producers.  The  base  of  the  stack 
flue  sets  on  a  level  with  the  bottom  of  the  checker  chambers,  but  the 
stack  proper  begins  at  the  charging  floor  level. 

The  Furnace  Proper:  The  furnace,  itself,  is  a  rectangular  brick 
structure,  supported  on  the  sides  and  ends  by  vertical  steel  buck-stays  in 
the  form  of  channels  or  slabs,  four  to  five  and  one  half  inches  thick  and 


210  OPEN  HEARTH  PROCESS 

\ 

eleven  inches  wide,  and  bound  together  at  their  tops,  both  longitudinally 
and  crosswise,  by  stays  and  tie  rods.  The  most  recently  constructed 
furnaces  have  a  capacity  rated  at  100  tons.  Such  a  furnace  is 
approximately  eighty  feet  in  length  and  twenty  feet  in  width,  outside  dimen- 
sions over  all.  Ten  sets  of  buck-stays  on  the  front  and  rear  sides,  and 
four  or  six  sets  on  the  ends  are  required  to  furnish  the  requisite  support 
against  expansion  of  the  brick  work.  The  buck-stays  are  held  in  place  by 
12-inch  channels  placed  at  their  tops.  These  channels  extend  entirely 
around  the  furnace,  those  along  the  sides  being  securely  tied  with  bolts 
and  clamps  to  those  crossing  the  ends  of  the  furnace.  The  front  and 
rear  buck-stays  are  united  by  tie-rods  which  are  two  and  one-half  inch 
steel  rounds;  the  ends  of  these  extend  through  the  buck-stays  and  are 
threaded  to  receive  nuts  to  hold  them  in  place  so  that  they  can  be  tightened 
and  loosened  according  to  the  expansion  and  contraction  of  the  furnace. 
The  foundation  under  the  furnace  proper  is  built  of  concrete,  and  is  of 
such  depth  and  shape  as  to  bear  the  superimposed  load  with  reasonable 
safety.  It  is  usually  in  the  form  of  two  large  piers,  with  an  arched 
opening  separating  them.  The  furnace  proper  comprises  the  hearth,  the 
side  walls,  and  the  roof. 

The  Hearth  is  constructed  as  follows:  On  top  of  the  concrete  foun- 
dation is  placed  a  layer  of  three  feet  or  more  of  second  quality  fire  brick, 
and  upon  these  is  laid  a  two  foot  layer  of  first  quality  fire  brick  in  which 
a  number  of  15  inch  I-beams  are  placed  to  act  as  a  bottom  anchorage  for 
the  vertical  buck-stays  which  surround  the  furnace;  a  nine  inch  layer  of 
magnesite  brick  is  then  laid  on  top  of  the  firebrick,  and  upon  these  bricks, 
a  bottom  is  made  up  approximately  ten  and  one-half  inches  thick  with  a 
mixture  of  burned  magnesite,  75%,  and  ground  basic  slag,  25%,  which  is 
sintered  into  place.  Dolomite  may  be  substituted  for  the  magnesite,  but 
in  this  case  the  bottom  must  be  much  thicker  than  when  magnesite  is 
used.  When  complete,  the  hearth  has  the  form  of  a  shallow  dish  whose 
sides  extend  up  to'  the  level  of  the  charging  doors.  In  order  to  obtain  this 
shape  the  succeeding  courses  of  magnesite  brick  are  stepped  back,  until 
the  normal  thickness  of  side  wall,  about  thirteen  and  one-half  inches,  is 
reached.  The  exact  hearth  dimensions,  inside,  between  fifteen  and  sixteen 
feet  in  width  and  about  forty  feet  in  length,  are  dependent  upon  the  desired 
maximum  capacity  of  the  furnace  and  incidental  features.  The  depth  is 
such  that  the  bath  of  molten  metal  will  be  from  twenty  to  twenty-four 
inches  deep  The  back  wall  of  the  hearth  is  pierced  at  its  exact  center  for 
the  tapping  hole,  which  is  about  eight  inches  in  diameter  and  is  provided 
on  the  outside  with  a  removable  cast  iron  lip  for  receiving  the  end  of  the  steel 
spout,  the  function  of  which  is  to  conduct  the  molten  steel  from  the  furnace 
to  the  steel  ladle  at  the  time  of  tapping.  The  slag  hole  is  placed  about 
fifteen  feet  from  the  tap  hole  and  near  the  upper  edge  of  the  hearth.  It  is 
surrounded  with  magnesite  brick  and  is  provided  with  an  iron  casting  at 
its  base  for  the  attachment  of  the  cinder  spout. 

The  Walls  are  begun  on  the  top  course  of  magnesite  brick  that  sur- 


CONSTRUCTION  OF  FURNACE  211 

rounds  the  upper  edge,  or  brim,  of  the  hearth.  They  are  built  of  silica 
brick,  are  about  thirteen  and  one-half  inches  thick  and  extend  to  a  distance 
of  about  eight  feet  above  the  charging  floor  level.  The  back  wall  is  built 
up  solid  except  for  the  tapping  hole  and  slag  hole,  but  the  front  wall 
contains  the  arched  doorways  for  charging.  The  doors  are  usually  five 
in  number,  the  middle  one  being  in  the  middle  of  the  furnace,  and  are  so 
placed  that  their  bases,  or  sills,  are  a  few  inches  above  the  slag  line. 
Each  opening  is  provided  usually  with  a  water  cooled  cast  steel  frame, 
placed  between  two  buck-stays  to  which  it  is  fastened,  and  is  closed  by  a 
water  cooled,  fire  brick  lined  cast  iron  or  steel  door  that  may  be  lifted 
vertically  either  by  hydraulic  or  electric  power.  A  wicket,  or  peep  hole, 
is  placed  on  the  center  line  near  the  bottom  of  each  door. 

The  Roof  over  the  hearth  is  made  of  silica  brick,  about  twelve  inches 
thick,  and  is  arched  from  front  to  back  only  in  the  newer  furnaces,  but 
sometimes,  also  from  end  to  end  in  older  types.  The  roof  is  built  inde- 
pendent of  the  walls,  and  rests  on  skew  back  brick  set  in  water  cooled 
skew  back  channels  that  are  riveted  or  bolted  to  the  buck-stays  of  the 
furnace. 

The  Bulk  Heads  which  form  the  ends  of  the  hearth  below  the  ports 
were  originally  built  of  solid  brick  work  and  were  a  source  of  much  trouble, 
as  they  burned  out  rapidly.  These  difficulties  were  all  avoided  by  replac- 
ing much  of  this  brick  work  with  a  large,  hollow  cast  steel  box  with  open 
ends  to  provide  for  air  cooling.  The  inside  surfaces  of  the  bulk  heads 
are  made  of  magnesite  brick. 

The  Ports :  The  air  and  gas  ports  at  each  end  of  the  furnace  are  built 
at  an  angle  to  the  bath,  so  that  the  flame  is  directed  against  the  bath  and 
away  from  the  roof.  In  order  to  protect  the  roof  and  promote  the  mixing 
of  the  gas  and  air,  the  air  enters  above  the  gas.  The  bricks  separating 
the  two  ports  are  protected  by  a  water  cooling  system.  Where  natural 
gas  is  used,  unless  the  furnace  was  constructed  for  producer  gas,  there  is 
but  one  port  at  each  end  of  the  furnace,  the  gas  entering  on  each  side  of 
either  end  of  the  furnace  behind  a  bridge  wall,  which  extends  across  the 
furnace  in  front  of  the  well,  or  up-take,  from  the  checkers.  This  wall  is 
usually  made  of  magnesite  brick,  though  chrome  brick  is  well  suited  for 
the  purpose,  and  is  about  thirteen  and  one-half  inches  thick  and  nine  inches 
high. 

The  Up-and-Down-Takes  are  the  vertical  flues  which  connect  the 
air  and  gas  ports  with  the  slag  pockets  and  the  fan-like  flues  leading  to 
their  respective  checker  chambers.  They  are  built  of  silica  brick  and  are 
not  water  cooled.  In  producer  gas  fired  furnaces  there  is  a  pair  of  up-and- 
down-takes  for  air  at  each  end  of  the  furnace,  the  two  in  each  pair  being 
at  opposite  sides  of  the  furnace.  The  up-and-down-takes  for  the  gas  rise 
with  their  centers  coincident  with  the  center  line  of  the  furnace  and  may 
stand  out  with  three  walls  exposed,  designated  as  the  dog-box  type,  or 
be  built  in  between  the  air  flues.  For  a  100-ton  producer  gas  fired  furnace 
these  flues  are  each  four  feet  by  three  feet,  inside  dimensions. 


212  OPEN  HEARTH  PROCESS 

Arrangement  of  Up-and-Down-Takes  for  Natural  Gas,  Coke  Oven 
Gas,  Powdered  Coal  and  Tar:  The  construction  of  the  up-and-down- 
takes  in  a  natural  gas  fired  furnace  is  much  simpler,  as  it  is  only  necessary 
to  have  one  up-take  for  the  air  at  each  end  of  the  furnace.  This  up-take 
in  modern  furnaces  is  circular,  with  a  diameter  of  about  six  and  one  half 
feet,  and  is  therefore  called  the  well.  The  air,  as  it  rises,  is  deflected 
downward  toward  the  bath  by  the  port,  which  is  arched  from  front  to 
back  but  is  straight,  longitudinally,  with  a  downward  slope  toward  the 
hearth.  This  roof  is  usually  about  nine  inches  thick,  except  near  the 
neck  where  it  joins  the  roof  of  the  furnace.  Here  it  increases  to  twelve 
inches  on  account  of  this  point  being  subjected  to  the  greatest  wear. 
The  bridge  wall  previously  described,  which  crosses  the  port  adjacent 
to  the  up-take,  causes  the  incoming  air  to  roll  down  past  the  opening  from 
the  gas  pipes,  one  of  which  enters  at  each  side  of  the  port.  Thus,  there  are  in 
all  four  pipes  to  a  furnace.  These  gas  pipes  have  a  diameter  of  four  inches. 
The  main  supply  pipe  usually  passes  over  an  entire  row  of  furnaces. 
A  branch  line,  provided  with  a  meter,  a  valve,  and  a  three  way  cock,  leads 
to  each  furnace,  where  it  again  branches  into  the  four  inch  pipes  which 
enter  the  ports.  For  tar  and  powdered  coal  the  same  construction  as  for 
natural  gas  has  been  employed,  because,  so  far,  these  substances  have  been 
used  only  as  a  substitute  for  the  latter  fuel  when  the  supply  became  low. 
Both  these  substitutes  are  introduced  into  the  furnace  by  inserting  the 
nozzles  of  the  burners  through  small  openings  in  the  brick  work  closing 
the  ends  of  the  furnace,  one  burner  at  each  end  of  the  furnace  being  required. 

Slag  Pockets:  The  slag  pockets  are  chambers  at  the  bottom  of  the 
up-and-down-take  flues.  Their  functions  are  to  serve  as  flues  to  conduct 
the  gases  to  and  from  the  checkers  and  to  catch  any  solid  matter  carried 
over  with  the  products  of  combustion,  thereby  preventing  most  of  this 
slag  material  from  reaching  the  checkers  and  clogging  them  up.  The 
pockets  are  designed  large  enough  so  that  only  in  extreme  cases  do  they 
have  to  be  cleaned  out  more  than  once  every  run.  In  the  100-ton  producer 
gas  fired  furnace,  they  are  about  three  feet  six  inches  wide,  and  eight  feet 
high.  The  two  at  each  end  of  the  furnace  are  separated  by  a  three  foot 
silica  brick  wall.  The  outside  walls  are  two  feet  seven  and  one  half  inches 
thick  for  the  air,  and  three  feet  for  the  gas  side;  the  former  have  an  inside 
lining  of  silica  brick,  set  against  first  quality  fire-brick,  while  the  latter  is 
made  of  silica  brick  only.  The  floor  and  roof  are  covered  inside  with 
silica  brick,  the  latter  being  arched  on  a  radius  of  half  the  width  of  the 
pockets.  One  end  of  each  pocket  merges  into  a  short,  fan-like  flue,  called 
a  neck,  which  leads  to  the  top  of  its  regenerator  chamber. 

Regenerators  for  Producer  Gas:  The  regenerators,  of  which  there 
are  two  pairs  to  a  furnace,  are  built  out  in  front  of  the  furnace  and  under 
the  charging  floor,  about  half  below  and  half  above  the  casting  floor 
level.  They  are  separated  from  the  furnace  by  a  distance  of  about 
four  feet.  Each  pair  is  made  up  of  one  checker  chamber  for  gas  and  one  for 


CONSTRUCTION  OF  FURNACE 


213 


214 


THE  OPEN  HEARTH  PROCESS 


Fia.  26.     Longitudinal  Vertical  Section  of  100-Ton  Open  Hearth  Furnace, 


S/L/CA 


CONSTRUCTION  OF  FURNACE 


215 


Showing  Slag  Pockets,  Flues,  Ports  and  Hearth. 


216  OPEN  HEARTH  PROCESS 

air,  arranged  so  that  the  outer  wall  of  the  gas  chamber  is  nearly  in  line 
with  the  end  of  the  furnace.  The  gas  chamber  is  always  smaller  than  the  air 
chamber,  because  the  larger  volume  of  air  is  necessary  to  burn  the  gas  and 
assist  in  the  oxidation  of  the  bath.  The  total  space  actually  occupied 
by  the  checkers  in  all  four  chambers  is  from  120  to  150  cubic  feet  per  ton  of 
furnace  capacity.  For  a  100-ton  furnace  the  volume  of  the  checkers  in 
the  air  chamber  is  between  3500  and  3600  cubic  feet  while  the  corresponding 
volume  in  the  gas  chamber  is  between  2500  and  2600  cubic  feet. 

The  gas  chambers  on  such  a  furnace,  measured  inside,  are  about 
thirty-one  feet  long,  eight  feet  wide  and  sixteen  and  one  half  feet  high  from 
the  bottom  to  the  base  of  the  roof,  which  is  arched  to  rise  twenty-three 
to  twenty-five  inches  higher.  The  air  chambers  are  of  the  same  length 
and  height,  but  are  about  eleven  and  one  half  feet  wide,  and  the  arch 
in  the  roof  rises  about  thirty-four  inches.  The  walls  of  both  gas  and  air 
chambers  are  built  usually  with  nine  or  thirteen  and  one  half  inches  of 
common  brick  on  the  outside  and  thirteen  and  one  half  inches  of  first 
quality  fire  brick  on  the  inside,  and  are  reinforced  on  the  two  sides  and 
the  free  ends  by  channel  buck  stays  and  tie  rods.  At  some  plants  the 
two  chambers  in  a  pair  are  built  en  bloc  with  a  single  dividing  wall 
between  them.  In  this  plan  of  construction  the  dividing  wall  is  about  three 
feet  thick  and  is  built  entirely  of  first  quality  fire  brick.  The  floors  of  the 
chambers  are  started  usually  with  a  nine  inch  layer  of  concrete,  which  is  fol- 
lowed with  a  heavy  coat  of  tar  as  a  water  proofing.  On  the  tar  is  laid 
another  nine  inch  layer  of  concrete,  then  four  and  one  half  inches  of  common 
brick  and  four  and  one  half  inches  of  first  quality  fire  brick.  On  this  floor, 
are  laid  nine  inch  fire  brick  withe  walls,  which  divide  the  gas  and  air 
chambers  longitudinally  into  three  and  four  flues,  respectively,  to  a  height 
of  about  four  feet.  These  walls  are  spanned  by  fire  brick  tile,  size, 
3"xl2"x31",  and  on  these  tile,  the  checker  work,  of  best  quality  fire  brick 
size,  4M"*4J$'xlO£i",  is  begun  and  continued  to  within  about  three  and 
one  half  feet  of  the  top  of  the  gas  chamber,  or  to  within  about  four  feet 
of  the  top  in  the  air  chambers.  The  arched  roofs  of  the  regenerators 
are  of  fire  brick  and  thirteen  and  one  half  inches  thick.  The  checker 
work  is  separated  from  the  flues  leading  to  the  slag  pockets  by  a  solid 
wall  which  rises  to  their  top.  This  wall  aids  much  in  preventing  slag 
and  dust  from  being  carried  into  the  checkers.  But  in  spite  of  all 
precautions,  some  dirt  is  carried  over  into  the  chambers,  which  causes 
them  to  become  choked  eventually,  when  the  furnace  must  be  closed  down 
until  the  checkers  are  cleaned  or  replaced. 

Regenerators  for  Natural  and  Coke  Oven  Gases:  At  some  plants 
where  natural  gas  or  coke  oven  gas  is  used,  as  for  example  at  Homestead 
and  Clairton  where  natural  gas  was  originally  the  only  fuel  employed,  the 
gas  chamber,  in  addition  to  the  regular  air  chamber,  is  utilized  to  preheat 
the  air.  The  original  idea  was  to  construct  the  regenerative  chambers  so 
that  in  case  gas  producers  were  built,  the  change  in  fuels  would  not  necessi- 


CONSTRUCTION  OF  FURNACE  217 

tate  a  rebuilding  of  the  furnace;  but,  now,  the  chambers  for  natural  gas 
are  all  being  constructed  in  this  manner,  because  it  was  found  that  when 
two  air  checkers  at  each  end  of  the  furnace  are  employed,  better  results 
are  obtained  than  when  only  one  is  used.  Where  one  large  checker  is 
operated,  the  air  and  stack  gases,  instead  of  flowing  to  all  parts  of  the 
chamber,  tend  to  take  a  direct  course  through  the  center,  thus  markedly 
decreasing  the  efficiency  of  the  chamber. 

Regenerators  for  Powdered  Coal :  The  use  of  powdered  coal  for  fuel 
introduces  a  serious  difficulty  in  the  operation  of  the  regenerators  because 
of  the  large  percentage  of  ash  that  is  carried  over  into  the  chambers  by 
the  draught.  This  fume  soon  clogs  the  ordinary  checkers  to  such  an  extent 
that  they  are  no  longer  efficient.  Two  different  types  of  regenerators, 
namely,  the  arched  and  columnar  types,  designed  with  the  idea  that  they 
would  permit  the  ash  to  be  cleaned  out  of  the  chamber  without  tearing 
out  the  brick  work,  have  been  tried;  but  as  the  ash  fuses  upon  the  bricks, 
these  schemes  are  impracticable  and  have  consequently  been  abandoned 
in  favor  of  the  old  style  of  construction.  But  instead  of  the  usual  checker 
brick  a  large  tile,  measuring  about  24"x9"x4",  has  been  substituted,  which 
gives  larger  openings  for  the  passage  of  the  gases.  This  construction 
appears  to  be  much  more  satisfactory  than  either  of  the  others  that  have 
been  mentioned. 

Flues  and  Valves:  While  the  openings  into  the  slag  pockets  are  at 
the  top  of  the  checker  work,  the  openings  for  the  ingress  and  egress  of 
gases  at  the  opposite  end  of  the  checker  chamber  are  at  the  bottom.  Here 
the  small  flues  formed  by  the  withe  walls  open  into  a  large  one  which  leads 
to  the  stack  flue  in  the  case  of  the  air  chambers,  or,  in  the  case  of  the  gas 
chambers,  to  a  three-way  water  sealed  valve, one  of  the  best  types  of  which  is 
represented  by  the  Ahlen  valve.  Another  branch  of  this  valve  leads  to 
the  stack  and  the  third  to  the  gas  main.  These  valves,  together  with  the 
dampers  and  mushroom  valves  in  the  flues  from  the  air  chambers,  supply 
the  means  by  which  the  reversals  of  the  flame  are  made.  In  the  modern 
furnaces,  these  valves  and  dampers  are  connected  so  that  the  reversal  of 
the  air  and  gas  currents  take  place  simultaneously.  All  the  valves  and 
dampers  are  controlled  from  the  charging  floor.  Since  natural  gas,  and 
also  coke  oven  gas,  cannot  be  preheated  without  decomposing  them,  the 
valve  system  in  furnaces  using  these  fuels,  as  well  as  those  using  powdered 
coal,  is  much  simpler  than  for  those  using  producer  gas. 

The  Stack :  The  stack  for  each  furnace  must  be  of  such  size  and  height 
as  to  supply  sufficient  draught  to  the  furnace.  It  is  lined  with  first  quality 
fire  brick,  and  usually  has  an  inside  diameter  of  5  feet  and  a  height  of  from 
140  to  160  feet  above  the  charging  floor.  The  shell  is  made  of  Muich  boiler 
plate.  It  usually  rests  on  a  concrete  foundation,  on  the  same  level  as  the 
floor  of  the  checker  chambers,  and  at  this  level  it  has  openings  for  flues 
from  the  gas  and  air  chambers,  as  previously  described.  For  controlling  the 
draft  a  damper  is  placed  in  the  main  flue  at  its  entrance  to  the  stack.  With  new 
or  clean  checkers  this  damper  partly  closes  the  main  flue,  but  as  the  checker 
becomes  clogged,  it  is  raised  from  time  to  time  as  required. 


218  OPEN  HEARTH  PROCESS 

SECTION   IV. 

OPERATION  OF  A   BASIC   OPEN   HEARTH — PURIFYING  THE   METAL. 

Furnace  Attendants  and  Their  Duties:  For  the  work  on  each 
furnace,  three  men,  a  first  helper,  a  second  helper  and  a  cinder-pit-man,  are 
needed,  and  besides  these,  there  is  a  foreman,  called  a  melter  foreman,  in 
charge  of  a  number  of  furnaces.  Ordinarily,  the  first  helper  has  charge  of  the 
furnace  except  at  the  tapping  of  a  heat.  He  informs  the  charging  machine 
operator  of  the  amount  of  ore  the  charge  will  require  and  how  and  where 
to  place  the  various  parts  of  the  charge;  he  regulates  the  heating  of  the 
furnace;  runs  off  the  slag;  directs  any  repairs  necessary  during  the  operation; 
and  has  charge  of  working  the  heat,  that  is,  making  the  necessary  additions 
of  ore,  pig,  spar,  etc.  to  prepare  the  steel  for  tapping.  But  when  the  heat 
is  ready  to  tap,  the  melter  foreman  takes  charge.  The  first  helper,  subject 
to  the  supervision  of  the  melter,  actually  taps  the  heat,  and,  after  doing 
so,  he  directs  the  repair  of  the  bottom  and  helps  make  up  the  banks  and 
clean  up  the  steel  spout.  The  second  helper  is  next  in  charge;  he  keeps 
a  supply  of  dolomite,  feed  ore,  fluorspar,  ferro-manganese  and  ferro-phos- 
phorus  on  hand  and  places  the  solid  recarburizing  additions  on  the  platform 
convenient  to  the  ladle.  He  helps  to  work  the  heat,  digs  the  plug  out  of 
the  tapping  hole  when  the  heat  is  ready  to  tap,  keeps  the  tapping  hole 
open  and  clean  while  the  furnace  is  being  rabbled,  and  assists  in  making 
up  the  banks  of  the  furnace  preparatory  to  recharging.  He  also  attends 
to  the  plugging  of  the  tapping  hole,  relines  the  steel  spout  after  each  heat 
and  cleans  up  around  the  furnace.  The  cinder-pit-man  attends  to  the 
cleaning  of  the  pits,  from  which  the  slag  and  metal  must  be  removed  after 
each  heat.  In  addition,  he  assists  in  making  bottom  at  his  own  furnace 
and  all  the  others  under  his  melting  foreman.  The  melter,  or  foreman, 
usually  has  charge  of  a  group  of  six  or  seven  furnaces.  He  takes  charge  of 
any  furnace  in  his  group  when  any  serious  difficulty  arises,  and  he  always 
has  charge  of  the  tapping  of  the  heat.  He  receives  an  order  for  the  kind  of 
steel  desired  from  the  steel  distributor,  so  when  the  tapping  time  of  a  heat 
is  near,  he  orders  the  recarburizer  and  moulds  necessary,  and  takes  charge 
of  the  furnace  when  the  carbon  is  but  a  few  points  above  the  tapping  point. 
He  decides  when  the  heat  is  ready,  gives  the  order  to  tap,  and  directs  the 
addition  of  the  recarburizers.  He  gives  the  order  for  lifting  the  ladle  when 
the  steel  is  out  of  the  furnace,  superintends  the  teeming  of  the  steel,  and 
inspects  the  bottom  of  the  furnace  after  the  heat  is  out. 

Preparation  of  the  Furnace  for  Its  First  Charge:  Starting  a  new 
furnace  is  an  operation  that  requires  a  great  deal  of  care  in  order  to  avoid 
injuring  the  brick  work  and  to  prevent  explosions,  especially  when  producer 
gas  is  used  for  fuel.  The  complete  preparation  of  the  furnace  may  be  said 
to  take  place  in  four  stages,  known  as  drying,  heating,  making  bottom 
and  washing.  The  drying  is  begun  very  slowly  with  wood  or  gas  fires, 
and  requires  about  twenty-four  hours,  during  which  time  all  the  con- 
nections to  the  stack  on  both  ends  of  the  furnace  are  left  open.  The 


CHARGING  RAW  MATERIALS  219 

temperature  is  then  gradually  increased  for  about  another  twenty  hours. 
When  the  furnace  has  almost  reached  a  red  heat  inside,  the  products  of 
combustion  are  led  off  through  only  one  set  of  checkers  for  three  or  four 
hours,  then  gas  is  turned  on  carefully  and  the  real  heating  is  begun, 
which  requires  about  twenty-four  hours  more.  During  this  time,  the 
flame  is  reversed  at  intervals  of  about  an  hour  at  first,  then  more  often, 
in  order  to  heat  up  both  sets  of  checkers  evenly  and  uniformly.  When  a 
slag-melting  temperature  has  been  reached,  finely  ground  magnesite  is 
thrown  into  the  furnace  to  cover  the  joints  between  the  magnesite  brick, 
and  a  little  finely  ground  basic  cinder  is  scattered  on  top  of  it.  About 
twelve  hours  is  required  for  these  additions  to  fuse  and  make  the  bottom 
solid.  The  making  of  the  bottom  is  then  begun.  For  this  purpose  burned 
magnesite  is  much  preferred,  but  as  this  substance  is  sometimes  very 
expensive,  calcined  dolomite  is  employed  as  a  substitute.  With  the 
former,  the  procedure  is  about  as  follows: — A  mixture  of  burned  magn- 
esite, 75%,  and  basic  cinder,  25%,  both  ground  to  pass  a  half  inch  screen, 
is  scattered  over  the  bottom  and  sides  of  the  hearth  to  a  depth  of  about 
a  half  inch,  and  allowed  to  sinter.  At  the  end  -of  about  three  hours,  the 
gas  is  turned  off,  and  another  layer  of  the  mixture  is  thrown  in;  and  this 
procedure  is  repeated,  at  the  same  intervals  of  time,  until  the  bottom 
and  banks  have  been  built  up  to  the  desired  thickness  of  about  eleven 
inches,  which  occupies  about  ten  days  in  all.  The  tapping  hole  is  next  cut 
through  from  the  outside,  to  terminate  on  the  bottom,  and  is  then  filled 
up  with  burned  dolomite,  held  in  place  by  a  cap  of  clay  on  the  outside. 
The  furnace  is  then  ready  for  the  wash  heat.  About  twenty  tons  of  basic 
cinder  is  charged  and  melted.  This  melt  is  rabbled  up  against  the  banks 
so  that  every  part  of  the  hearth  is  made  solid,  and  is  then  tapped  out. 
Burned  dolomite  is  now  piled  on  top  of  the  banks  as  high  as  possible, 
when  the  furnace  is  ready  to  receive  its  first  charge. 

Charging:  The  first  charge  consists  of  limestone,  scrap,  and  cold  pig 
iron;  neither  ore  nor  hot  metal  are  used  on  a  new  bottom  until  it  shows 
it  is  not  absorbing  iron  and  is  absolutely  solid.  Trade  heats,  of  approxi- 
mately half  scrap  and  half  hot  metal  arechargedfor  the  first  half  dozen  heats, 
after  which  the  percentage  of  hot  metal  is  increased  as  rapidly  as  possible  to 
the  normal.  The  materials  in  the  charges  vary  for  different  kinds  of  heats, 
but  in  general,  a  so-called  Monell  heat  requires  from  75%  to  100%  hot  metal 
and  a  trade  heat  less  than  75%  hot  metal.  In  each  case,  the  remainder  of  the 
metallic  part  of  the  charge  consists  of  scrap,  while  the  ore  and  limestone  are 
varied  to  suit  the  conditions.  An  example  of  each  as  used  on  a  100-ton  funrace 
follows: 

Monell.  Trade. 

Limestone ....  20000  pounds.  Limestone ....   17000  pounds. 

Ore 40000  pounds.  Ore. .  •. 10000  pounds. 

Scrap 45000  pounds.  Scrap 95000  pounds. 

Pig  Iron 165000  pounds.  Pig  Iron 115000  pounds. 


220  OPEN  HEARTH  PROCESS 


In  place  of  ore,  briquettes,  made  from  blast  furnace  flue  dust,  or  heating 
furnace  cinder  may  be  substituted.  The  charge,  with  the  exception  of  the 
molten  iron,  is  brought  to  the  furnace  in  the  charging  boxes  previously 
mentioned,  and  charged  by  machine.  Hot  metal  is  brought,  either  from 
the  mixer  or  from  the  blast  furnace  direct,  in  ladles  and  is  then  poured 
into  the  furnace  through  a  runner  that  is  introduced  at  one  of  the  doors 
for  the  purpose.  Other  additions  in  small  quantities  are  thrown  in  by 
hand  through  the  doors.  At  one  plant,  furnaces  with  removable  tops  are 
provided,  in  order  to  make  it  possible  to  charge  very  large  pieces  of  scrap 
which  would  not  pass  through  ordinary  doors.  At  all  plants  advantage  is 
taken  during  repairs  to  old  furnaces  to  charge  such  large  scrap  through 
the  top  before  the  roof  is  put  on.  As  to  the  grade  of  the  materials  in  the 
charge,  it  is  preferable  to  have  an  iron  low  in  sulphur  and  silicon  because 
the  former  element  is  only  partly  removed  in  the  furnace,  if  at  all,  and  the  lat- 
ter, upon  being  oxidized  to  silica,  rapidly  cuts  away  the  banks.  A  manganese 
content  between  1%  and  2%  is  also  desirable,  as  it  assists  somewhat  in  the 
removal  of  the  sulphur.  As  there  is  almost  a  complete  elimination  of 
phosphorus  in  the  process,  the  quantity  of  this  element  in  the  charge  is 
not  of  great  importance  up  to  one  per  cent.  As  previously  indicated, 
the  pig  iron,  in  order  to  save  time  and  conserve  heat,  is  charged  in  the 
molten  state  whenever  possible. 

The  Order  of  Charging  the  Raw  Materials:  As  to  the  order  of 
charging,  the  limestone  is  always  charged  first  for  these  reasons:  If  it 
were  charged  on  top  of  the  scrap,  for  example,  it  would  act  as  an  insulator 
and  thus  prolong  the  melting  period;  it  would  all  go  to  make  up  a  part 
of  the  first  slag,  which  would  be  too  thick  and  viscous  to  work  well;  it 
would  be  drawn  off  with  this  slag  in  the  run  offs,  thus  leaving  very  little 
lime  in  the  furnace  to  hold  the  phosphorus  in  the  latter  stages  of  the  refine- 
ment; and,  finally,  the  benefits  to  be  derived  from  the  lime  boil,  to  be 
described  later,  would  be  lost.  Upon  the  limestone,  will  be  charged  the 
ore,  or  briquettes,  which,  if  any  is  needed,  will  vary  in  amount  according 
to  the  nature  of  the  rest  of  the  charge  and  the  heating  capacity  of  the 
furnace.  In  order  to  hasten  oxidation,  ore  may  also  be  added  from  time 
to  time  during  the  later  stages  of  the  process.  The  scrap  is  next  charged, 
and  if  cold  pig  iron  is  used,  it  is  charged  with  the  scrap.  The  gas,  which  is 
usually  but  partly  turned  on  during  the  charging  is  then  turned  on  full,  and 
the  first  or  melting  stage  begins.  If  hot  metal  is  to  be  charged,  it  is  not  added 
until  the  melting  period  is  well  advanced. 

Melting  Down  the  Charge:  Heat  is  imparted  to  the  charge  partly 
through  radiation  from  the  incandescent  particles  in  the  flame.  The  fuel 
should,  therefore,  burn  with  a  full  long  flame  reaching  almost  from  end  to 
end  of  the  furnace.  But  the  flame  should  never  extend  through  the  ports 
and  down-takes,  as  it  would  then  rapidly  fuse  the  brick  of  those 
flues  and  waste  the  fuel.  For  the  same  reason,  the  flame  should 
be  directed  downward  from  the  port  and  not  be  allowed  to  impinge  on  the 


PURIFICATION  PEROIDS  221 

roof.  The  light  scrap  and  pig  iron,  if  any  is  added  to  the  solid  charge, 
begin  to  melt  first.  During  the  melting  much  of  these  materials  is  oxidized, 
so  that  there  is  formed  both  molten  metal  and  oxides,  which  trickle  down 
over  the  scrap  to  the  bottom.  A  slight  amount  of  molten  slag  and  metal 
is  thus  present,  on  the  bottom  of  the  furnace,  before  the  hot  metal, 
i.  e.,  molten  pig  iron,  is  charged.  Reversals  of  the  flame  should  occur 
every  fifteen  to  twenty  minutes  during  this  period,  and  care  must  be  taken 
not  to  overheat  the  roof,  for  too  high  a  temperature  will  cause  the  bricks 
in  a  new  roof  to  spall,  and  those  in  an  old  one  to  fuse.  Silica  brick  frequently 
sweat,  that  is,  fuse  slightly,  but  this  condition  does  no  harm  and  indicates 
a  favorable  temperature  in  the  furnace.  Care  must  be  taken  with  the  roof 
and  checkers  in  a  new  furnace,  especially,  and  the  temperature  must  be 
kept  relatively  low  for  the  first  ten  heats  or  more,  after  which  time  the 
gas  may  be  gradually  increased  until  the  full  working  temperatupe  is 
attained. 

The  Addition  of  the  Hot  Metal:  The  molten  metal  can  usually  be 
added  in  about  two  hours  after  the  charging  of  the  solid  materials  is  begun. 
The  exact  time  for  adding  this  metal  is  governed  by  the  temperature  of 
the  solid  charge.  Evidently  this  temperature  should  be  above,  or  at  least 
as  high  as,  that  of  the  melting  point  for  pig  iron.  This  statement  does  not 
imply  that  the  scrap,  which  has  a  much  higher  melting  point  than  pig 
iron,  should  be  completely  melted.  Indeed,  a  delay  in  the  addition  of  the 
molten  metal  until  the  scrap  is  all  melted  may  be  very  undesirable,  for 
net  only  would  the  scrap  be  excessively  oxidized,  but  the  high  temperature 
combined  with  the  excess  oxides  present  would  result  in  a  too  violent 
reaction,  and  much  foaming  of  the  bath  and  loss  of  metal  due  to  the  rapid 
generation  and  evolution  of  carbon  monoxide  would  result. 

The  Purification  Periods:  The  purification  of  the  hot  metal,  after 
it  is  introduced  into  the  furnace,  is  brought  about  through  the  oxidizing 
influence  of  the  iron  oxides  and  the  fluxing  properties  of  the  limestone. 
While  both  oxidizing  and  fluxing  reactions  are  actually  taking  place  in  the 
furnace  at  the  same  time,  the  action  of  the  iron  oxides  must  be  considered 
as  preceding  that  of  the  limestone,  for  the  acid  impurities  must  first  be 
oxidized  before  they  can  be  neutralized,  or  fluxed,  by  the  bases.  It  is 
evident  that  the  fluxing  action  may  immediately  succeed  the  oxidation, 
but  the  conditions  set  up  by  the  manner  of  charging  the  limestone  tends 
to  retard  its  calcination  and  thus  to  separate  the  two  actions.  Now,  the 
carbon  monoxide  generated  by  the  action  of  the  iron  oxides  upon  the  carbon 
of  the  pig  iron  is  at  first  evolved  in  a  manner  quite  different  from  that 
of  the  same  gas  formed  later  on  in  the  process  or  of  the  carbon  dioxide 
from  the  calcination  of  the  limestone,  and  this  difference  is  indicated  by 
the  way  in  which  the  bath  is  agitated.  Hence,  the  fui  nacemen  have  fallen 
into  the  habit  of  speaking  of  the  purification  as  taking  place  in  stages, 
known  as  the  ore  boil,  the  lime  boil,  and  the  working  period.  The  third 


222  OPEN  HEARTH  PROCESS 


is  the  stage  that  follows  the  complete  calcination  of  the  limestone.  In 
order  that  the  reader  may  understand  what  is  implied  by  these  terms, 
the  changes  that  occur  during  the  purification  of  the  metal  are  discussed 
under  these  three  headings. 

The  Ore  Boil :  Proper  chemical  testing  will  show  that  the  purification 
of  the  molten  iron  begins  immediately  after  it  is  charged  into  the  furnace, 
and,  with  the  exception  of  carbon,  the  oxidation  of  which  is  not  completed 
till  the  heat  is  ready  to  tap,  progresses  very  rapidly.  So,  in  about  two 
hours  practically  all  of  the  silicon  and  the  greater  part  of  the  manganese 
will  have  been  oxidized,  and  the  former,  then  in  the  form  of  silica,  will 
have  been  neutralized,  some  with  lime,  but  the  greater  portion  with  the 
oxides  of  iron  and  manganese,  and  will  have  become  slag.  Some  of  the 
sulphur,  also,  will  have  been  oxidized,  particularly  if  the  sulphur  content 
of  the  hot  metal  was  high,  but  as  the  oxides  of  this  element  are  volatile 
and  the  high  temperature  tends  to  decompose  the  sulphites  and  sulphates, 
only  a  part  of  the  oxidized  sulphur  is  retained  by  the  slag,  and  the  remainder 
is  carried  off  with  the  products  of  combustion.  A  very  small  portion  of 
this  element  finds  its  way  into  the  slag  as  sulphides,  probably  as  manganese 
sulphide.  With  the  silicon  and  manganese,  the  phosphorus  is  also  rapidly 
attacked  by  the  iron  oxide,  which  not  only  oxidizes  it,  but  neutralizes  the 
resulting  oxides  of  this  element.  These  iron  phosphates,  which  are  easily 
reduced,  likewise  pass  into  the  slag,  where  the  iron  oxide  is  replaced  with 
lime,  thus  forming  the  calcium  phosphates,  which  are  very  stable 
compounds.  During  all  this  time  the  carbon  is  also  being  slowly  oxidized. 
This  action,  which  at  first  takes  place  near  the  surface  of  the  metal,  results 
in  the  evolution  of  carbon  monoxide  in  the  form  df  tiny  bubbles,  which 
become  entangled  in  the  viscous  slag  and  cause  it  to  foam.  Consequently, 
the  slag,  thus  permeated  with  little  gas  cells,  occupies  much  more  than  its 
natural  space  in  the  furnace.  Carbon  dioxide  is  also  evolved  by  the  lime- 
stone, which  begins  to  be  calcined  more  and  more  rapidly  as  the  temperature 
at  the  bottom  rises;  but  as  the  gas  resulting  from  the  decomposition  of 
the  limestone  escapes  in  relatively  large  bubbles,  it  causes  Very  little  of 
the  foaming. 

The  Run  off:  When  the  slag  level  has  been  raised  to  a  height  a  little 
above  that  of  the  bottom  of  the  openings  for  the  doors  and  is  threatening 
to  break  through  the  dolomite  dykes  built  up  just  inside  these  openings, 
the  dolomite  with  which  the  slag  hole  is  dammed  is  cleaned  out  of  this 
opening,  and  the  excess  slag  is  allowed  to  flow  through  the  cinder  spout 
into  the  cinder  pit  or  into  a  slag  pot  placed  below  to  receive  it.  This 
tapping  of  slag  is  known  as  the  run=off.  The  bases  in  this  first  slag 
are  composed  chiefly  of  iron  and  manganese  oxides,  the  lime  and  magnesia 
being  relatively  low.  It  is  not  unusual  for  these  slags  to  contain  iron 
as  oxide  equivalent  to  30%  metallic  iron,  and  as  they  constitute  about 
40%  of  the  total  slag  formed  in  the  process,  they  represent  the  source  of 
greatest  loss  of  metal  for  the  entire  process.  Practically  all  of  the  iron 
contained  in  the  run-off  is  in  the  ferrous  condition. 


PURIFICATION  PERIODS  223 

The  Lime  Boil:  The  action  of  the  ore  and  other  iron  oxides,  formed 
by  the  oxidizing  flame,  upon  the  carbon  will  be  somewhat  violent  for  two 
hours  or  more,  during  which  time  the  scrap  will  have  been  almost  com- 
pletely melted  down.  Gradually,  however,  as  the  carbon  content  decreases 
and  the  temperature  of  the  bath  rises,  the  ore  boil  subsides,  or  changes 
its  character,  and,  the  calcination  of  the  limestone  becoming  more  rapid, 
the  lime  boil  is  in  the  ascendency.  The  lime  boil  is  characterized  by  a 
rising  of  the  lime  to  the  top  of  the  bath  and  by  a  violent  bubbling  of  the 
bath,  caused  by  the  rapid  evolution  of  carbon  dioxide  gas  from  undecom- 
posed  limestone  which  still  remains  on  the  bottom,  and  also  in  part  by 
the  continued  oxidation  of  carbon  in  the  molten  metal.  These  activities 
play  important  parts  in  the  process.  Thus,  not  only  does  the  violent 
bubbling  caused  by  the  evolution  of  the  carbon  dioxide  gas  agitate  the 
metal  and  slag,  thus  mixing  them  and  exposing  the  metal  to  the  oxidizing 
influence  of  the  flame,  but  a  part  of  the  gas,  at  least,  unites,  directly  or 
indirectly,  with  the  carbon  remaining  in  the  iron  to  form  carbon  monoxide. 
Furthermore,  by  rising  to  the  surface,  the  lime  may  replace  iron  and 
manganese  oxides  in  the  phosphates,  sulphates  and  silicates  present  and 
thus  become  a  part  of  the  slag,  while  any  excess  lime  is  also  taken  up  and 
goes  to  increase  the  basicity  of  the  slag.  This  property  of  the  slag  makes 
it  more  capable  of  retaining  both  the  phosphoric  and  silicic  acids  together 
and  renders  the  former  less  liable  to  be  reduced.  During  this  period  the 
flame  in  the  furnace  should  be  reversed  more  frequently  (about  every  15 
minutes)  in  order  that  the  temperature  of  the  bath  eventually  will  be  well 
above  the  melting  point  of  the  decarbonized  metal. 

The  Working  Period:  Since  all  the  impurities  except  carbon  have 
now  been  eliminated,  the  operations  during  this  period  aim  at  regulating 
the  properties  of  slag,  adjusting  the  carbon  content  of  the  steel,  and  raising 
the  temperature  of  the  bath  to  the  point  where  the  steel  may  be  tapped 
from  the  furnace  and  cast  into  ingots  before  it  begins  to  solidify.  In  order 
for  the  steel  to  be  teemed  without  difficulty,  this  temperature  should  be 
at  least  167°  C.  (300°  F.)  above  its  fusion  point.  Both  the  chemical  and 
the  physical  properties  of  the  slag  play  most  important  parts  in  the  basic 
process.  In  order  that  it  may  protect  the  metal  against  contamination 
by  sulphur  from  the  flame,  retain  the  impurities,  especially  phosphorus, 
and  promote  the  elimination  of  the  carbon,  the  slag  must  contain  a  large 
quantity  of  active  oxidizing  agents,  except  at  the  end  of  the  period,  and 
must  be  strongly  basic  at  all  times.  But  even  with  the  chemical  com- 
position of  the  slag  properly  adjusted,  its  activity  will  depend  upon  the 
fluidity  to  a  great  extent.  The  reagents  at  the  disposal  of  the  operator 
for  regulating  these  properties  are  iron  oxide,  limestone,  dolomite  and 
fluorspar.  The  iron  oxide  is  usually  in  the  form  of  lump  ore,  though  heating 
furnace  cinder  formed  on  a  magnesite  bottom  may  be  used. 

Methods  of  Working  the  Heat  :  There  are  two  general 
methods  of  working  heats,  and  briefly  described,  they  are  as  follows: 


224  OPEN  HEARTH  PROCESS 

The  first  method  is  somewhat  like  the  Bessemer,  that  is,  the  carbon  content 
of  all  heats  is  reduced  to  a  common  point,  about  .10%,  when  the  steel  will 
be  tapped  and  the  per  cent,  of  carbon  will  be  raised  to  that  desired  by 
the  addition  of  recarburizers.  In  the  second  method  the  carbon  is  caught 
on  the  way  down,  that  is,  the  carbon  content  is  reduced  to  a  point  slightly 
under  that  required,  to  allow  for  the  carbon  contained  in  various  additions, 
and  the  bath  of  steel  is  then  tapped.  Medium  and  low  carbon  steels  are 
usually  worked  by  the  first  method,  while  high  carbon  steels  maybe  worked 
by  either. 

Testing  for  Carbon:  So  toward  the  end  of  the  lime  boil,  or  earlier  if 
it  appears  that  the  carbon  content  of  the  bath  is  dropping  rapidly,  the  first 
helper  will  begin  taking  tests  in  order  to  follow  the  progress  of  the  heat.  These 
tests  he  takes  by  securing  a  small  test-spoon  full  of  the  metal,  which  he 
pours  into  a  small  rectangular  mould.  As  soon  as  the  metal  has  solidified 
in  the  mould,  it  is  removed  by  jarring  the  mould  while  in  an  inverted 
position;  the  test  piece  is  nicked  in  the  center,  rapidly  cooled  with  water,  and 
then,  while  still  warm  enough  to  dry  itself,  it  is  broken  with  a  heavy 
sledge  hammer.  From  the  fracture  thus  exposed,  the  carbon  content, 
which  determines  how  the  heat  is  to  be  treated,  can  be  very  accurately 
estimated.  In  order  that  the  temperature  of  the  bath  may  be  raised  to  a 
point  sufficiently  high  for  tapping  by  the  time  the  carbon  is  reduced  to  the 
point  aimed  at,  it  is  desirable  that  the  carbon  content  of  the  bath  at  the  end 
of  the  lime  boil  should  be  forty  to  fifty  hundredths  of  a  per  cent.  (40  to  50 
points)  higher  than  that  desired  at  tapping. 

Control  of  Carbon  and  Temperature:  If,  as  occasionally  happens, 
the  carbon  is  nearly  all  removed  while  the  bath  is  yet  too  cold  to  tap  and  pour 
successfully,  it  is  difficult,  on  account  of  its  inactivity,  to  bring  the  heat 
up  to  the  proper  tapping  temperature  without  danger  of  burning,  or  over- 
oxidizing  the  steel  and  unduly  increasing  the  wear  on  the  roof  of  the  furnace. 
A  heat  working  under  such  conditions  is  known  as  a  sticker.  To  prevent 
this  over-oxidizing,  pigging  up  is  resorted  to,  that  is,  the  carbon  content 
is  held,  or  kept  constant,  by  adding  pig  iron,  which  also  aids  in  raising  the 
temperature  by  producing  a  little  boil  in  the  bath.  Usually,  however,  there 
will  be  fifty  to  eighty  points  of  carbon  to  be  removed  from  the  bath  after  the 
lime  boil.  Therefore,  as  soon  as  the  first  helper  sees  that  the  lime  is  about 
all  up,  he  will  first  take  a  test,  then  see  that  all  lumps  of  unfused  matter, 
or  nigger  heads,  are  melted  and  that  the  slag  is  sufficiently  fluid.  To 
bring  about  the  rapid  melting  of  the  unfused  bodies  and  increase  the  fluidity  of 
the  slag,  fluorspar  sufficient  for  the  purpose  will  be  added.  Then  to  hasten  the 
elimination  of  the  carbon,  it  may  be  necessary  to  ore  down,  that  is,  additions 
of  ore  or  heating  furnace  cinder  will  be  made  from  time  to  time  as  required  to 
reduce  the  carbon  content.  After  each  addition  of  oxide  has  had  time  to  act,  a 
test  is  taken.  During  the  last  half  hour,  in  some  cases  the  last  hour,  the  heat 
is  in  the  furnace,  no  ore  will  be  added.  Some  foremen  erroneously  believe  that 
the  elimination  of  carbon  at  this  point  may  be  hastened  by  stirring  the  bath 


WORKING  THE  HEAT  225 

with  a  long  steel  bar,  a  process  known  as  shaking  down,  while  others 
will  merely  allow  the  metal  to  lie  in  the  hearth  undisturbed.  In  the  case 
of  low  carbon  heats  the  flame  will  now  be  reversed  in  the  furnace  about 
every  ten  minutes  in  order  to  raise  the  temperature,  and  as  soon  as  the 
tests  show  that  the  carbon  is  within  three  or  four  points  of  the  desired 
content,  the  melter,  or  foreman,  is  notified.  He  takes  additional  tests  for 
the  carbon  content  and  also  for  temperature,  orders  the  recarburizers, 
inspects  the  furnace,  ladle,  etc.,  and  completes  the  arrangements  for  tapping 
the  heat. 

Judging  the  Temperature  of  the  Bath :  For  judging  the  temperature 
of  the  bath,  two  very  simple  tests  are  employed  by  the  furnacemen.  One 
of  these  tests  consists  of  quickly  inserting  the  end  of  a  long  steel  bar  or  rod 
into  the  bath  of  metal  and  slowly  moving  it  from  side  to  side  until  the 
part  immersed  in  the  metal  melts  off.  Then  the  bar  is  withdrawn,  and 
from  the  appearance  of  the  hot  end  the  condition  of  the  bath  with  respect 
to  temperature  may  be  judged.  Thus,  if  the  bath  is  too  cold,  this  end  of 
the  rod  will  be  pointed;  if  too  hot,  it  will  show  nicks  on  the  sides  near  the 
end;  but  if  the  temperature  is  right,  the  end  of  the  rod  will  have  melted  off 
so  as  to  leave  a  clean,  square  end.  The  second  method  depends  upon  the 
quite  evident  fact  that  the  higher  the  temperature  of  a  fluid  the  longer 
it  will  remain  fluid  in  contact  with  cold  surroundings.  It  is  carried  out 
simply  by  quickly  withdrawnig  a  test-spoonful  of  the  molten  steel  from 
the  bath  and  at  once  pouring  it,  rather  slowly,  but  at  a  fixed  rate  of 
flow,  out  of  the  spoon.  The  operator  judges  the  temperature  of  the  steel 
by  the  way  it  flows  and  by  the  extent  and  thickness  of  the  skull  it  leaves 
in  the  spoon.  By  long  practice  with  these  methods  the  workmen  become 
very  expert  in  making  these  relative  determinations  of  temperature. 

Tapping:  The  furnace  should  be  manipulated  so  that  a  tapping  tem- 
perature is  reached  before  the  carbon  content  has  been  reduced  to  the 
tapping  point,  as  otherwise  some  difficulty  will  be  experienced  with  high 
carbon  steels  in  holding  the  bath,  if  the  carbon  is  to  be  caught  on  the  way 
down,  while  with  low  carbon  steels,  it  will  be  difficult  to  reach  a  tapping  tem- 
perature or  the  metal  will  be  over-oxidized,  with  the  result  that  it  will  tend 
to  be  both  hot  short  and  cold  short  unless  deoxidizers  such  as  spiegel,  f  erro- 
manganese,  or  pig  iron,  are  added.  Prolonging  the  life  of  the  heat  at  this  point 
in  order  to  reduce  the  sulphur  content  is  very  bad  practice  for  the  double 
reason  that  the  removal  of  the  sulphur  is  uncertain  and  the  cure  is  worse  than 
the  disease.  The  proper  temperature  for  tapping  low  carbon  heats  is  1600° 
C.,  or  a  little  higher,  while  for  heats  in  which  the  carbon  is  caught  on  the 
way  down,  the  tapping  temperature  may  be  about  100°  C.,  lower.  To  ac- 
complish the  tapping,  the  second  helper  digs  out  from  the  rear  the  mud  plug  and 
most  of  the  dolomite  with  which  the  tapping  hole  is  closed,  after  which  the  hole 
is  opened  by  driving  outward  the  dolomite  remaining  in  it  by  inserting  a 
tapping  rod  through  the  wicket  of  the  center  door  in  the  front  of  the  furnace. 
The  steel  then  flows  through  the  hole  out  of  the  furnace  and  down  the 


OPEN  HEARTH  PROCESS 


spout  into  the  ladle.  Since  the  tapping  hole  is  on  a  level  with  the  bottom 
of  the  hearth,  the  greater  part  of  the  steel  is  out  of  the  furnace  before  any 
slag  appears,  and  this  fact  permits  of  recarburization  in  the  ladle.  It  is  not 
advisable  for  the  recarburizing  materials  to  be  allowed  to  come  into 
contact  with  the  slag,  since  some  of  the  phosphoric  acid  in  the  slag  may 
be  reduced  and  the  phosphorus  re-enter  the  steel.  The  tapping  spout  and 
ladle  are  so  placed  as  to  direct  the  stream  of  molten  metal  a  little  to  one 
side  of  the  center  of  the  ladle,  as  the  swirling  motion  tends  to  mix  and  make 
more  homogeneous  the  contents  of  the  ladle. 

SECTION   V. 

FINISHING  THE   HEAT — MAKING  STEEL  FROM  THE  PURIFIED   METAL. 

Methods  of  Finishing  the  Steel:  The  process  of  finishing  the  steel 
consists  in  making  such  additions  as  are  required  to  produce  the  kind  and 
grade  of  steel  desired,  and  with  few  exceptions  these  additions  are  made 
immediately  before  and  after  tapping  the  heat.  The  methods  of  making 
the  necessary  additions  to  produce  the  various  kinds  and  grades  of  steel 
differ  somewhat,  not  only  for  the  different  grades  but  in  different  works 
making  the  same  grades.  For  example,  the  ferro  manganese  and  spiegel 
are  preferably  added  to  the  steel  in  the  ladle  and  in  the  molten  state,  but  not 
all  plants  are  at  present  equipped  to  melt  these  materials,  and  ferro  manganese 
is  still  generally  added  in  the  solid  form.  For  the  plain  steels  the  methods  of 
making  additions  for  carbon  and  manganese  may  be  briefly  stated  in  the 
following  tabulated  form. 

High  Carbon  Steels.    (C.60%  to  1.30%) 

Method  I.  Carbon  is  caught  on  the  way  down;  ferro-manganese 
is  added,  and  coal,  if  needed,  in  the  steel  ladle. 

Method  II.  The  steel  is  tapped  with  the  carbon  at  .10%;  molten 
spiegel  mixture  is  added  in  the  steel  ladle. 

Method  III.  The  carbon  in  the  bath  is  eliminated  to  .10%;  sufficient 
molten  pig  iron  is  added  in  the  furnace  at  the  time  of  tapping  to  raise  the  carbon 
content  almost  to  the  point  desired.  Then  ferro-manganese  may  be  added  to 
the  ladle  to  make  up  the  deficit  in  the  carbon,  and  supply  the  manganese 
deficit  left  by  the  pig  iron. 

Medium  Carbon  Steels.  (C.  .30%  to  .70%) 
Method  I.    The  steel  is  tapped  with  a  carbon  content  of  .10%;  molten 

spiegel  mixture  is  added  in  the  steel  ladle. 

Method  II.     The  carbon  in  the  bath  is  eliminated  to  .10%;  molten  pig 

iron  is  added  in  the  furnace  and  ferro-manganese  in  the  ladle  as  in  III  for  high 

carbon   steels. 

Low  Carbon  Steels.     (C.  less  than  .40%) 

Method  I.  For  dead  soft  steels  the  carbon  content  is  reduced  as  low 
as  possible  without  danger  of  over-oxidizing  the  steel,  and  ferro-manganese 
is  added  in  the  steel  ladle. 


FINISHING  THE  HEAT  227 

Method  II.  The  carbon  content  is  reduced  to  .10%  and  ferro-manga- 
nese  is  added  alone,  or  ferro-manganese  and  coal  are  added  in  the  steel 
ladle.  In  case  a  large  quantity  of  ferro  is  required,  some  furnacemen 
prefer  to  add  a  part  of  it  in  the  furnace  just  before  the  tapping  hole  is  opened. 

Method  III.  For  finishing  very  low  carbon  steels  neither  molten  spiegel 
nor  molten  pig  iron  are  used  on  account  of  the  difficulty  of  weighing  and  keep- 
ing molten  small  quantities  of  these  materials.  But  in  large  furnaces,  pig 
iron  may  be  used,  if  the  carbon  content  is  more  than  .20%,  as  in  Method  II  for 
medium  carbon  steels. 

Other  Elements:  The  additions  for  other  elements  will  be  made  about 
as  follows: — Copper  is  added  in  the  solid  form  to  the  steel  fifteen  to  twenty 
minutes  before  the  heat  is  tapped.  Sulphur  is  always  added  before  the  ferro 
additions.  Ferro  silicon  is  necessarily  added  in  the  steel  ladle;  while  it  is  the 
common  practice  to  add  ferro  vanadium  by  dropping  it  into  the  stream  of 
molten  metal  in  the  runner,  or  spout,  as  it  is  flowing  into  the  ladle.  As 
nickel  is  chemically  negative  to  iron,  none  is  lost  in  the  furnace,  so  nickel  steels 
are  made  by  charging  nickel  steel  scrap,  then  adding  pig  nickel  in  sufficient 
amount  to  make  up  the  deficiency,  as  shown  by  chemical  analysis,  about 
thirty  or  forty  minutes  before  tapping.  The  same  practice  may  be 
employed  in  the  case  of  steel  requiring  copper  and  chromium,  but  a 
comparatively  large  part  of  the  latter  element  is  lost  through  oxidation 
in  the  furnace.  Chromium  is  added  in  the  form  of  ferro  chromium. 

Some  Features  that  Make  the  Finishing  of  the  Steel  Difficult:    It 

requires  considerable  experience  to  finish  steel  properly,  for  there  are  a 
number  of  circumstances  that  tend  to  complicate  the  operations.  For 
example,  the  addition  of  ferro,  on  account  of  its  carbon  content,  will  always 
slightly  raise  the  carbon  content  of  the  steel,  though  it  is  primarily  added 
to  increase  the  manganese.  Similar  conditions  also  prevail  in  the  use  of 
other  ferro  alloys  and  pig  iron.  Again,  there  is  always  a  loss  of  the 
elements  added,  except  in  the  case  of  copper  and  nickel,  and  this  loss, 
different  for  each  element,  will  vary  with  any  one  under  different  con- 
ditions. Hence,  the  efficiency  of  these  substances  is  never  100%.  Furthermore, 
it  is  seldom  any  of  the  elements  can  be  obtained  in  pure  form  for  this  purpose, 
and  the  substance  containing  the  element  sought  may  vary  in  its  content  of 
that  element.  The  various  substances  used,  their  efficiencies,  and  the  amount 
of  each  element  present  in  the  bath  at  the  tapping  of  a  normal  heat  are 
indicated  in  the  following  table. 


228 


OPEN  HEARTH  PROCESS 


Table  31.     Data  Relating  to  Materials  Used  in  Finishing  Steel. 


Material  Added 

Element 
Sought 

Percentage  of  Element 
in  Bath 

Efficiency 
When  Added  in 

Furnace 

Ladle 

Pig  Nickel                .    . 

Ni 
Cr 
Cu 

S 

c 
c 

Mn 
Mn 
Mn 
C 
P 
Si 
V 

.00  unless  Ni.  scrap  used 
.00      "       Cr.      " 
.00      "       Cu.     " 
.040 
Any  desired 

.10  to  .20 
.10  to  .20 
.10  to  .20 
.10  to  Any  desired 
.010 
.00 
.00  unless  V.  scrap  used 

98% 
80% 
99% 
Never 

95% 
50% 
50% 
Never 

Never 

66%-70% 
44%-  50% 
Never 

85%-90% 
80%-90% 
100% 
75% 
65—70% 
90% 

Ferro  Chromium  

Pig  Copper  

Stick  Sulphur  
Anthracite  Slack  

Pig  Iron  

Ferro  Manganese  
Spiegel 

Ferro  Phosphorus  
Ferro  Silicon  
Ferro  Vanadium  

In  the  following  table  will  be  found  an  analysis  typical  of  each  of  these 
substances. 
Table  32.    Representative  Analyses  of  Materials  Used  in  Finishing  Steel. 


Fe 

% 

C 

% 

Mn 

% 

P 

% 

S 
% 

Si 
% 

V 

% 

Cr 

% 

Ni 

% 

Cu 
% 

Ferro  Manganese  
'     Phosphorus  
"     Silicon,  Electric  
"      Blast  Fee  
'     Chrome  

13.03 
79.97 
49.44 
87.465 
22.05 
42.65 
75.68 

6.80 
1.10 
.55 
1.52 
6.36 
1.58 
4.39 

79.35 
.18 
.016 
.42 
.35 
6.25 
19.13 

.16 
18.00 
.075 
.080 
.003 
.010 
.053 

.65 
.018 
.015 
.79 
1.06 
.028 

.66 
.10 
49.90 
10.50 

.48 
10.49 

.72 

37.96 

69.96 



97.00 

99.00 

Vanadium  

Spiegel  

Pig  Nickel... 

Pig  Copper  . 

.17 

Stick  Sulphur  .   . 

100.00 
.030 

Pig  Iron  

94.00 

3.80 

1.00 

1.00 

Given  the  weight  and  composition  of  the  metal  in  the  bath,  the  desired 
composition  of  the  finished  steel,  and  the  composition  and  efficiencies  of  the 
substances  to  be  added,  the  calculation  of  the  amounts  of  the  various  additions 
is  a  simple  problem  in  arithemetic. 

Teeming:  As  soon  as  the  stream  from  the  furnace  no  longer  contains 
any  steel,  the  spout,  or  runner,  is  removed,  and  the  steel  ladle  is  lifted  by 
the  crane  and  carried  to  the  pouring  platform,  where  the  steel  is  teemed 
into  the  ingot  moulds  ready  to  receive  it.  Teeming  is  not  to  be  confused  with 
pouring.  While  the  latter  logically  refers  to  the  way  the  metal  is  let  out  of 
the  ladle,  usage  has  made  pouring  synonymous  with  casting, which  refers  to  the 
manner  of  introducing  the  metal  into  the  ingot  mould.  Thus,  if  the  metal 


TEEMING  AND  SAMPLING  229 

is  introduced  into  the  mould  through  its  top,  the  resulting  ingot  is  said  to  have 
been  top  poured  or  top  cast;  but  if  through  its  bottom  by  means  of  runners, 
the  ingot  is  said  to  have  been  bottom  poured  or  bottom  cast.  Teeming  and 
top  pouring  are  accomplished  in  the  following  manner :  The  ladle  is  placed  with 
its  nozzle  over  the  center  and  about  a  foot  from  the  top  of  the  first  mould  in  the 
mould  train,  when  the  stopper  is  raised  and  the  steel  flows  through  the 
nozzle  into  the  mould  below.  In  teeming  the  heats,  care  must  be 
taken  that  neither  the  stream  of  metal  nor  any  part  thereof  be  allowed 
to  strike  the  sides  of  the  moulds,  for  these  splashes  of  metal  will  adhere 
to  the  mould,  which  quickly  chills  them,  and,  being  coated  on  their  surfaces 
with  a  film  of  oxide,  they  may  cause  ingot  defects  which  later  appear  as 
slivers  in  the  rolled  steel.  As  the  first  mould  is  filled,  the  stream  is  stopped, 
and  by  means  of  a  hydraulic  pusher  the  train  is  moved  forward  so  as  to 
bring  the  next  mould  under  the  nozzle  of  the  ladle.  At  some  plants  the 
teeming  is  done  from  an  overhead  crane,  which  moves  the  ladle  from  mould 
to  mould.  After  the  ladle  has  been  emptied  of  steel,  the  slag  remaining 
in  it  is  dumped  into  cinder  cars  and  ultimately  conveyed  to  the  cinder  yard. 
In  the  meantime,  the  mould  train  is  hauled  to  the  stripper.  On  soft  steel 
and  special  heats,  unless  there  is  a  high  percentage  of  manganese  or  silicon 
present,  aluminum  is  thrown  into  the  moulds,  about  two  ounces  to  each  ton, 
in  order  to  further  deoxidize  and  quiet  the  steel.  Aluminum  is  especially 
effective  in  overcoming  wildness  because  of  its  strong  tendency  to  combine 
with  oxygen.  Of  this  small  amount  added  practically  none  remains  in  the 
metal,  so  that  this  aluminum  exerts  no  influence  as  an  alloy  in  the  steel. 

Sampling:  The  sampling  of  the  heat  for  chemical  analysis  is  accom- 
plished when  the  heat  is  half  teemed  by  slackening  the  stream  from  the 
ladle,  whilst  a  spoon  of  suitable  size  is  held  under  the  nozzle  and  filled  with 
the  molten  metal,  which  is  immediately  poured  into  a  test  mould  specially 
designed  for  the  purpose.  The  test  mould  may  be  of  either  one  of  two 
types,  which  careful  and  extensive  experiments  have  shown  to  give  test 
pieces  most  uniform  in  composition  and  most  free  from  blow  holes.  One 
of  these  types  is  a  split  mould  that  gives  a  test  piece  having  a  section  \Y^ 
inches  square  and  a  length  of  nearly  5  inches,  with  a  flared  opening  about  2 
inches  deep  to  facilitate  pouring.  The  other  type  is  a  small  cup  shaped 
mould  that  gives  a  test  piece  3%  inches  in  diameter  at  the  top  and  2^ 
inches  at  the  bottom  with  a  depth  of  2^  inches.  Upon  being  taken  from 
the  mould,  the  test  piece  is  immediately  stamped  with  its  heat  number, 
and  is  then  delivered  to  the  chemical  laboratory  for  analysis.  Experiments 
have  shown  that  a  sample  taken  in  this  way  most  nearly  represents  the 
average  composition  of  the  heat. 

SECTION   VI. 

KEEPING  THE   FURNACE  IN   REPAIR. 

Preparation  of  the  Furnace  for  the  Next  Charge:  After  the  runner 
is  lifted  and  thus  detached  from  the  furnace,  the  cinder  and  any  steel  that 
remains  in  the  furnace  flow  out  of  the  tapping  hole  into  the  cinder  pit. 


230  OPEN  HEARTH  PROCESS 


The  second  helper  must  keep  the  tapping-hole  open  until  everything  that 
can  be  removed  from  the  furnace  has  flowed  out.  Fluorspar  is  usually 
thrown  in  on  the  slag  left  to  be  sure  that  it  flows  out  and  does  not  build 
up  on  the  bottom  of  the  furnace.  Often,  holes  will  be  found  in  the  bottom, 
due  to  the  intrusion  of  steel  below  the  surface,  which,  boiling  there,  brings 
up  part  of  the  basic  material  forming  the  bottom.  Slag  and  steel  are  found 
in  these  holes  after  tapping  and  must  be  rabbled  out,  so  that  the  bottom 
can  be  properly  repaired.  After  all  the  steel  and  slag  are  removed  from 
these  holes,  they  are  filled  up  with  dolomite.  The  gas  is  left  on  to  keep 
the  slag  and  steel  fluid  during  this  process;  but  is  shut  off  as  soon  as  the 
repairs  to  the  bottom  have  been  completed.  Proceeding  to  the  next  step, 
the  second  helper  and  cinder-pit  man  remove  the  steel  that  has  chilled  in 
the  tapping  hole,  rake  out  and  free  the  hole  of  iron  and  close  it  up  with 
dolomite.  A  plug  of  clay  is  used  to  seal  up  the  outside  of  the  hole  and  hold 
the  dolomite  in  place.  The  banks,  which  have  been  cut  by  the  slag  from 
the  heat  just  out,  are  repaired  by  throwing  burned  dolomite  on  them  (3000 
to  4000  Ibs.  is  used  after  each  heat  in  a  100-ton  furnace);  and  the  furnace 
is  then  ready  for  charging  again. 

Furnace  Troubles:  In  the  operation  of  a  furnace,  troubles  of  a  very 
serious  nature  may  occur  at  any  time,  unless  the  furnace  is  watched  closely, 
and  carefully  handled.  These  troubles  present  so  many  possibilities  and 
are  so  varied  that  space  will  permit  of  little  more  than  an  enumeration 
of  some  of  the  more  serious  ones  here.  Thus,  the  tap-hole  may  break  out 
prematurely  if  it  is  not  properly  tamped  and  capped,  or  it  may  become 
hopelessly  clogged  if  it  is  not  properly  cleaned  after  each  heat.  Sometimes, 
sections  of  the  bottom  become  detached  and  rise,  due  to  the  buoyant  force 
of  the  metal,  and  when  this  occurs  the  heat  must  be  tapped  at  once,  and 
no  more  heats  may  be  charged  until  the  damaged  bottom  is  repaired.  The 
ports  require  constant  attention  to  prevent  them  from  building  up  or  melting 
down,  and  thus  changing  the  angle  of  the  flame,  which  would  then  tend  to 
over-heat  some  part  of  the  furnace  and  would  be  rendered  less  effective 
in  heating  the  bath.  Leaks  may  occur  in  the  walls  of  the  up-and-down- 
takes,  which  result  in  the  gas  being  burnt  in  part  before  it  reaches  the 
hearth.  The  walls  and  roof  often  wear  out  long  before  the  rest  of  the 
furnace  needs  repairing.  Roofs  usually  last  for  about  300  heats.  The  roof 
can  be  repaired  in  a  few  hours,  and  a  cave-in  of  the  roof  is  of  a  serious 
nature  only  when  it  falls  in  near  the  end  of  a  heat.  The  most  disastrous 
mishap  that  can  occur  to  a  furnace  is  a  break-out.  Breakouts  may  be 
caused  by  several  things.  A  hole  near  a  bank  may  not  have  been  noticed 
or  may  have  been  insufficiently  repaired,  in  which  case  the  steel  works 
down  into  it  and  gradually  makes  it  deeper,  until,  finally,  the  metal  finds 
its  way  through  the  wall  and  out  of  the  furnace.  Sometimes,  owing  to  a 
thin  spot  on  the  banks  or  to  slag  having  reached  above  them  and  worked 
down  into  them,  the  slag  gradually  cuts  its  way  out  through  the  walls,  in 
which  case  it  is  usually  followed  by  steel,  as  the  hole  soon  becomes  low 
enough  to  reach  the  bath.  Such  mishaps  are  also  known  as  break-outs 


FURNACE  REPAIRS  231 


and  are  always  of  a  serious  nature.  Once  a  break-out  occurs,  the  tapping 
hole  should  be  opened  immediately,  and  as  much  as  possible  of  the  steel 
gotten  into  the  ladle  or  cinder  pit.  The  spread  of  cinder  and  metal  upon 
the  floor  where  the  break-out  has  occurred  can  be  limited  usually  by 
throwing  dolomite  around  it.  Finally,  after  about  600  or  700  heats,  the 
checker  work  has  become  so  badly  clogged  and  the  brick  work  is  so  eaten 
away,  that  it  becomes  necessary  to  close  down  the  furnace  for  general 
repairs,  during  which  the  greater  part  of  the  brick  work  may  be  torn  out 
and  rebuilt. 

Repair  Materials:  It  is  evdent  that,  for  making  up  the  bottom  and 
for  doing  the  repair  work  about  a  furnace,  much  depends  upon  the  materials 
employed.  Great  care  must  always  be  exercised  to  see  that  they  are  of 
the  right  chemical  composition,  and  best  suited  for  the  work  in  nand,  as, 
otherwise,  the  best  of  workmanship  in  making  the  repairs  will  go  for  naught. 
Therefore,  a  few  remarks  in  this  connection  should  be  of  interest. 

Dolomite  is  found  in  local  deposits  similar  to  those  of  limestone.  Like 
the  latter  it  varies  in  composition  through  quite  wide  ranges,  but  that 
suitable  for  open  hearth  work  will  have,  after  being  calcined,  approximately 
the  composition  shown  by  the  following  chemical  analysis:  Silica,  SiC>2, 
1.66%;  Iron  Oxide,  Fe2O3,  .94%;  Alumina,  A12O3,  1.24%;  Lime,  CaO, 
50.01%;  Magnesia,  MgO,  35.26%. 

Magnesite:  The  magnesite  used  before  the  European  war  was  im- 
ported from  Madelein  and  Budapest,  Austria,  and  was  brought  to  the  mill 
already  burned  and  ground.  It  was  used  on  the  furnace  bottom,  banks  and 
ports,  and  in  repair  work.  An  average  analysis  of  thirty-eight  cars  of  the 
imported  material  is  as  follows: — 

SiO2  Fe  Mn         A12O3         CaO  MgO       Ig.Loss 

2.07%  6.00%  .37%  1.63%  3.81%  84.11%  .52% 
Since  the  outbreak  of  the  war,  however,  deposits  of  this  material  in 
California  and  Washington  have  been  opened,  and  this  domestic  supply 
promises  to  replace  permanently  the  imported  material.  This  magnesite  is 
purer  than  the  imported,  and  for  that  reason  it  does  not  sinter  or  bond  so 
readily,  but  by  mixing  a  little  of  the  proper  fluxing  material  with  it,  this 
drawback  has  been  easily  overcome. 

Chrome  Ore:  Chrome  ore  is  still  imported,  as  the  limited  deposits 
so  far  discovered  in  the  United  States  and  Canada  are  of  an  inferior  grade. 
It  is  received  in  the  form  of  small  lumps.  It  is  ground  and  mixed,  in  a  wet 
pan,  with  one-half  magnesite,  and  is  used  in  repair  work  where  a  neutral 
substance  is  required,  such  as  in  patching  flues,  tapping  holes,  ports,  etc. 
An  analysis  of  an  average  sample  of  a  satisfactory  grade  of  this  ore  gave 
these  results: 

SiO2         FeO         MnO          A12O3         MgO         Cr2O3     Ig.  Loss 
9.02%      13.50%       .80%         10.82%      19.89%       42.66%      2.92% 


232  OPEN  HEARTH  PROCESS 

Besides  these  materials,  some  ganister  may  be  employed  at  some  of  the 
works,  while  all  plants  will  use  large  quantities  of  loam  and  of  fire  clay  for 
lining  furance  spouts  and  ladles,  for  making  up  stoppers,  and  for  other 
repair  work  of  minor  importance. 


SECTION  VII. 

CHEMISTRY  OP  THE   BASIC  PROCESS. 

Some  of  the  Principles  and  Conditions  Involved:  Having  followed 
the  procedure  of  making  steel  by  this  process,  the  reader  should  be  interested 
in  a  discussion  of  a  subject,  which  to  the  metallurgist,  at  least,  represents 
the  most  interesting  and  profitable  part  of  the  study,  namely,  the  chemistry 
of  the  process.  In  beginning  this  study  it  should  be  recalled  that  the 
purification  of  pig  iron,  which  is  the  first  of  the  two  main  steps  in  making 
steel,  includes  the  elimination  from  the  metal  of  the  four  elements,  silicon, 
manganese,  phosphorus  and  carbon,  and  that  the  principle  by  which  this 
elimination  is  effected  is  that  of  oxidation.  In  basic  open  hearth  processes, 
the  elimination  of  sulphur  may  also  take  place  to  a  greater  or  less  extent, 
depending  upon  the  amount  present,  but  is  never  to  be  considered  seriously 
as  a  principal  objective.  It  now  remains  to  be  pointed  out  that  this 
oxidation,  when  brought  about  indirectly,  that  is,  through  the  interaction 
of  these  elements  with  oxygen  bearing  compounds,  as  is  the  case  in  this 
process,  involves  two  other  principles  as  well.  These  are  the  principles 
of  reduction  and  neutralization,  for  it  is  manifestly  impossible  under  these 
conditions  that  one  substance  can  be  oxidized  without  another's  being 
reduced,  and  it  develops,  as  will  be  shown  later,  that  this  interaction  is 
made  possible  through  the  immediate  neutralization  of  the  oxidized  sub- 
stances. While  these  principles  and  the  reactions  by  which  the  purification 
is  brought  about  are,  when  considered  separately,  very  simple  and  can  be 
easily  understood,  they  are  somewhat  difficult  to  follow  in  the  actual 
working  of  the  furnace,  because  they  are  here  occurring  simultaneously 
and,  therefore,  tend  to  mask  each  other  in  the  effects  they  produce.  For 
this  reason  it  is  best  to  consider  the  subject,  first,  from  the  standpoint  of 
the  chemical  properties  of  the  elements  affected  and  of  the  oxygen  com- 
pounds of  these  elements  under  the  conditions  of  the  basic  open  hearth 
process. 

Properties  of  Iron  and  Its  Oxides:  One  of  the  most  marked  of  the 
chemical  properties  of  metallic  iron  is  its  tendency  to  combine  with  oxygen. 
Even  at  ordinary  temperatures  this  tendency  is  very  marked,  as  is  seen 
from  the  ease  and  quickness  with  which  it  combines  with  oxygen  and  water 
to  form  the  familiar  compounds  known  commonly  as  iron  rust.  These 


CHEMISTRY  OF  THE  PROCESS  233 

compounds  are  but  the  hydrated  sesqui-oxide,  or  per-oxide,  of  iron  contain- 
ing varying  amounts  of  combined  water,  as  represented  by  the  formula 
Fe2O3*xH2O.     This  tendency  of  iron  and  oxygen  becomes  stronger  as  the 
temperature  rises,  so  that  at  a  temperature  ranging  from  800°  to  900°,  or 
higher,  the  combination  becomes  very  rapid,  and  a  compound  quite  different 
from  those  composing  rust  is  formed.     It  is  commonly  known  as  Scale, 
and  is  represented  by  the  formula  FesO^  or  FeOFe2C>3.     These  facts  help 
to  explain  why  iron  is  seldom  found  in  nature  uncombined,  and  the  two 
compounds,  represented  by  the  formulas  given  above,  together  with  the 
carbonate  of  iron,  constitute  the  valuable  part  of  all  the  ores  of  iron.    The 
ore  used  in  all  our  furnaces  is  the  red  hematite,  which  for  the  purpose  of 
this  discussion,  may  be  considered  as  being  composed  of  the  sesqui-oxide, 
Fe2C>3,  and  gangue.    Besides  free  oxygen,  certain  compounds  may,  at  high 
temperature,  serve  as  sources  of  supply  of  oxygen  to  iron.    Among  these 
are  carbon  dioxide  and  water  vapor,  which  constitute  the  chief  products 
of  combustion  in  any  case  of  burning  a  fuel  in  the  presence  of  an  excess  of 
oxygen,  such  as  normally  exists  in  an  open  hearth  furnace.    The  heating 
of  free  iron  to  these  high  temperatures  in  contact  with  either  free  oxygen 
or  steam  always  results  in  the  formation  of  FeaO^  according  to  the  following 
reactions:— 3Fe+2O2=Fe3O4,   3Fe-r-4H2O=Fe3O4+4H2.     But  at  a  tem- 
perature of  1000  °C.  or  more,  with  iron  in  contact  with  carbon  dioxide,  another 
and  less  common  oxide,  FeO  is  formed,  thus  Fe+CO2=FeO-hCO.    Ferrous 
oxide,  FeO,  and  ferroso-ferric  oxide,  FeaO^  may  be  formed  in  the  furnace 
in  other  ways,  also,  one  of  which  is  by  the  progressive  reduction  of  Fe2C>3. 
If  Fe2(>3  be  heated  to  a  high  temperature  it  loses  oxygen  and  is  converted 
into  FeaO4.    This  change  takes  place  at  temperatures  between  1100°  and 
1200°  C.,  some  500  degrees  below  the  maximum  temperatures  of  the  open 
hearth.      If  FeO  be  formed  under  conditions  even  only  slightly  oxidizing, 
it  passes  into  FesO4.    Another  difference  in  the  properties  of  these  oxides, 
which  is  of  great  importance  in  considering  the  chemistry  of  the  open  hearth, 
is  seen  in  their  power  to  neutralize  acids.    Thus,  while  both  Fe2Os  and  FeO  ex- 
hibit very  marked  basic  properties  and  combine  rapidly  with  acid  oxides, 
FesO^  cannot  be  induced  to  form  corresponding  salts  at  the  temperatures  that 
prevail  hi  the  open  hearth.    Pure  scale,  FeaO^,  fuses  at  about  1450°  C.,  a  temper- 
ature easily  attainable  in  the  open  hearth,  and  it  dissolves  readily  in  either 
iron  or  calcium  silicates.    Ferrous  oxide,  FeO,  is  soluble  in  both  the  molten 
iron  and  the  slag,  and  though  the  amount  that  remains  dissolved  in  the  metal 
when  solid  is  small,  being  seldom  present  to  an  extent  greater  than  .315% 
the  equivalent  of  .07%  oxygen,  its  effects  are  very  harmful,  as  it  produces 
both  red  and  cold  shortness  in  the  metal.     With  metallic  manganese  it  gives 
the  following  reaction:     FeO+Mn=Fe-f-MnO.     MnO  is  not  soluble  in  the 
molten  metal,  which  fact  assists  in  accounting  for  the  efficiency  of  manganese 
as  a  deoxidizing  agent. 

The  Importance  of  Ferrous  Oxide,  FeO,  in  the  Part  Played  by  the 
Oxides  of  Iron  in  the  Process:  From  what  has  been  said  concerning  the 
properties  of  the  three  oxides  of  iron,  it  is  evident  that  ferrous  oxide,  FeO. 


234 


OPEN  HEARTH  PROCESS 


is  the  principal,  perhaps  the  only,  direct  oxidizing  agent  in  the  open  hearth 
process.  Although  iron  sesquioxide,  FesOa,  may  be  charged  into  the 
furnace,  much  of  this  oxide  is  transformed  by  the  heat  into  ferroso-ferric 
oxide,  FesO4,  before  it  has  an  opportunity  to  become  active.  Besides, 
since  the  impurities  are  held  in  solution  by  the  metal,  either  the  oxidizing 
agent  must  dissolve  in  the  metal,  a  condition  that  is  not  true  for  either  FesO4 
or  FesOs,  or  the  oxidation  of  the  impurities  must  occur  at  the  surface  of  contact 
between  metal  and  slag.  That  conditions  in  the  open  hearth  during  the  melt- 
ing period  tend  to  form  an  abundant  supply  of  ferrous  oxide  can  be  shown  by 
an  analysis  of  the  first  slag  formed,  as  is  illustrated  by  the  following  analyses 
of  samples  of  this  slag  taken  just  before  the  introduction  of  the  hot  metal. 


Table  33.     Analysis  of  First  Slag  Formed  in 
Open  Hearth  Heats 


Si02 

FeO 

Fe203 

MnO 

P205 

A1203 

CaO 

MgO 

S 
(S+S08 

% 

% 

% 

% 

% 

% 

% 

% 

/o 

Slag  from.  Fee., 

No.  9  

8.54 

61.05 

11.10 

2.31 

.26 

1.98 

9.13 

5.48 

.16 

Slag  from  Fee., 

No.  15  

1.00 

78.24 

15.31 

.81 

.14 

.37 

2.70 

1.12 

.25 

Concerning  the  neutralizing  powers  of  these  oxides,  FeO  must  also  act 
as  the  initial  base,  as  will  be  shown  later,  but  in  the  slag  Fe2Os  is  also 
capable  of  acting  as  a  base.  It  is  important  to  emphasize  these  facts  here 
because  of  their  influence  on  the  chemical  action  of  the  other  elements 
eliminated  during  the  purification  period,  for  their  action  depends  on  the 
conditions,  which  it  is,  therefore,  essential  to  define.  Briefly,  the  chief  of 
these  conditions  is  that  at  the  time  of  introducing  the  hot  metal  there  is 
present  in  the  furnace  a  slag  that  is  very  rich  in  ferrous  oxide. 


Properties  of  Silicon  and  Its  Oxide,  Silica:  Silicon  forms  but  one 
compound  with  oxygen  under  the  conditions  prevailing  in  the  open  hearth, 
and  this  compound  is  silica,  SiC>2.  The  tendency  of  silicon  to  combine 
with  oxygen  is  even  stronger  than  that  of  iron,  due  to  the  greater  heat  of 
formation  of  its  oxide,  so  that  it  is  capable  of  reducing  any  of  the  oxides 
of  the  latter,  and  upon  this  fact  depends  the  elimination  of  this  element 
from  the  molten  metal.  As  to  which  of  the  oxides  of  iron  is  the  active 
agent  in  the  oxidation  of  silicon,  there  can  be  little  doubt  but  that  ferrous 
.oxide,  FeO,  is  the  principal  one  that  suffers  direct  reduction  by  the  silicon, 
for,  as  already  indicated,  the  silicon,  either  as  an  alloy  or  a  compound  of 


CHEMISTRY  OF  THE  PROCESS  235 


iron,  is  distributed  throughout  the  mass  of  molten  metal,  and  it  is  necessary 
that  either  the  oxidizing  agent  also  dissolve  in  the  liquid  or  the  silicon  diffuse 
to  the  surface  of  the  metal  in  order  that  the  molecules  may  be  brought  into  that 
intimate  contact  required  to  effect  a  reaction.  The  oxidation  of  the  silicon, 
then,  is  represented  by  the  following  reaction:  Si-j-2FeO=SiO2+2Fe. 
Silicon,  however,  is  a  very  strong  acid,  so  that  if  this  reaction  occurs,  the  silica 
will  immediately  combine  with  ferrous  oxide  to  form  a  bisilicate,  a  tri-silicate 
or  some  still  more  acid  salt,  depending  upon  the  relative  amount  of  base 
available.  Since  this  oxidation  takes  place  with  only  a  limited  supply  of  ferrous 
oxide  present,  it  may  be  assumed  that  the  salt  requiring  the  least  base,  such  as 
the  tri-silicate,  would  be  formed.  If  so,  the  reaction  would  be  as  follows: 
3  SiO2-f-2FeO=(FeO)2-(SiO2)3.  If  the  bisilicate  is  formed,  the  reaction 
would  be  represented  thus:  SiC>2-|-FeO=FeO'SiO2.  Since  the  neutral- 
izing action  must  always  instantly  follow  the  oxidation,  it  is  perhaps  best 
to  represent  the  change  by  a  single  reaction,  which  can  be  done  by  com- 
bining the  first  two,  thus:  3Si+8FeO=(FeO)2'  (SiO2)3+6Fe.  The  ferrous 
silicate  is  in  the  fluid  state,  for  its  fusion  point  is  below  that  of  the  metal. 
It  is  of  lower  density  than  the  iron,  and,  therefore,  rises  to  the  surface, 
where  it  temporarily  forms  a  part  of  the  slag.  On  the  way  to  the  slag  it 
may  undergo  a  change  as  noted  later  under  manganese.  Once  in  the  slag, 
this  ferrous  silicate  is  capable  of  undergoing  many  changes.  The  first  of 
these  changes  is  probably  due  to  the  ability  of  the  silica  to  take  on  additional 
base.  Having  been  formed  in  a  region  where  there  is  only  a  limited  supply 
of  base,  the  silica  could  not  be  neutralized  to  the  extent  it  is  capable.  But 
now,  having  diffused  into  the  slag,  where  there  is  abundance  of  bases,  this 
trisilicate  may  become  a  monosilicate  with  either  a  monoxide  or  a  sesqui- 
oxide  base.  The  formation  of  the  monosilicate  with  the  monoxide  base, 
FeO,  may  be  represented  thus:  (FeO)2-(SiO2)3-|-4  FeO=3(FeO)2-SiO2, 
The  ferrous  oxide  thus  combined  cannot  act  as  an  oxidizer  and,  therefore, 
becomes  inactive.  However,  it  may  be  made  available  through  the  action 
of  lime  and  magnesia.  Both  these  bases  are  capable  of  replacing  ferrous 
oxide  in  the  manner  indicated  by  the  following  reactions:  — 


2  Mg0MgO)2-Si02+2  F 

The  ferrous  oxide  thus  liberated  is  now  subject  to  reduction,  and  available 
to  the  bath  for  further  use.  The  sources  of  supply  of  lime  and  magnesia 
are  the  stone  charged  into  the  furnace  and  the  lining  of  the  furnace  itself. 
These  alkaline  earth  silicates  constitute  the  major  portion  of  all  the  final 
slags  formed  in  the  process,  but  these  slags  are  never  free  of  iron,  for  they 
hold  its  oxides  in  solution. 

Properties  of  Manganese  and  Its  Oxides:  While  manganese  com- 
bines with  oxygen  in  several  different  proportions  to  form  an  equal  number 
of  different  oxides,  under  the  conditions  that  exist  in  the  basic  open  hearth 
only  one  of  these  oxides  is  formed,  namely,  the  manganous  oxide,  or 
protoxide  of  manganese,  MnO.  Like  silicon,  the  manganese  in  the  charge, 


236  OPEN  HEARTH  PROCESS 


being  alloyed  with  iron,must  be  oxidized  largely  through  the  agency  of  ferrous 
oxide.  But  as  silicon  is  capable  of  reducing  manganese  oxide,  there  appears 
little  chance  of  oxidizing  the  latter  until  the  former  element  has  been  largely 
eliminated  from  the  bath.  However,  there  is  much  evidence  to  show  that 
at  least  a  part  of  the  manganese  finds  its  way  into  the  slag  long  before  all 
the  silicon  has  been  oxidized.  This  fact  is  explained  by  the  assumption 
that  manganese  is  capable  of  replacing  iron  in  the  silicates  of  iron,  thus: 
FeO'SiO2+Mn=MnO-SiO2+Fe.or  (FeO)2-(SiO2)3+2Mn=(MnO)2>(SiO2)3 
+2  Fe.  With  this  idea  in  mind,  it  is  easy  to  conceive  the  simul- 
taneous elimination  of  both  these  elements,  in  which  elimination  the  ferrous 
oxide  plays  the  part  of  oxidizing  agent,  only,  and  manganese  fulfills  the 
office  of  the  base  for  the  neutralization  of  the  silica.  Such  a  change, 
involving  the  simultaneous  oxidation  of  silicon  and  manganese,  is  represented 
by  the  following  reaction:  3  FeO+Si+Mn=MnO-SiO2+3Fe.  When  this 
silicate  of  manganese  reaches  the  slag,  it  is  subject  to  the  same  changes  as 
are  the  corresponding  iron  oxide  silicates,  the  manganese  oxide  being 
eventually  set  free  by  lime  and  magnesia.  This  free  oxide  of  manganese, 
being  insoluble  in  the  metal,  remains  in  the  slag  as  such  as  long  as  the 
latter  is  rich  in  iron  oxides;  but  if  the  slag  should  be  depleted  of  its  oxides, 
then  manganous  oxide  is  liable  to  reduction,  in  which  event  the  resulting 
metallic  manganese  returns  to  the  bath.  Another  property  of  manganese, 
though  it  is  of  little  importance  in  ordinary  open  hearth  operations,  may 
be  mentioned.  It  refers  to  the  ability  of  manganese  to  replace  iron  in 
combination  with  sulphur.  Thus,  all  the  sulphur  contained  in  the  pig  iron 
or  steel  scrap  going  into  the  furnace  may  be  considered  as  being  combined 
with  this  element  and  in  the  form  of  manganese  sulphide.  This  substance 
is  slightly  soluble  in  the  slag  as  well  as  in  the  metal,  and  this  fact  accounts 
for  the  presence  of  small  amounts  of  sulphide  found  in  open  hearth  slags.  On 
the  surface  of  the  slag,  in  contact  with  an  oxidizing  flame,  manganese  sulphide 
is  subject  to  oxidation  according  to  this  reaction:  2  MnS+3O2=2  MnO+ 
2  SO2.  The  sulphur  dioxide,  SO2,  thus  formed  is  a  gas  and  may  escape  from 
the  furnace  with  the  products  of  combustion.  However,  it  is  evident  that 
the  quantity  of  sulphur  removed  in  this  way  must  be  very  small. 

Sulphur  and  Its  Oxides:  Owing  to  the  peculiar  properties  of  sulphur 
and  its  oxides,  they  are  subject  to  a  number  of  conflicting  influences,  under 
the  conditions  of  the  open  hearth  process,  that  render  the  removal  of  this 
element  very  uncertain.  As  an  element,  sulphur  combines  directly  with 
iron  to  form  iron  sulphide  and  is  easily  oxidized  to  form  oxides,  SO2  and 
SOs,  both  of  which  are  gaseous  acid  anhydrides,  and,  when  neutralized, 
form  sulphites  and  sulphates,  respectively.  At  temperatures  far  below  the 
lowest  working  temperature  of  the  open  hearth,  the  sulphites  and  sulphates 
of  the  heavier  metals,  like  iron,  for  example,  decompose  to  form  either  the 
sulphide  or  the  oxide  of  the  metal  and  sulphur  dioxide.  At  temperatures 
relatively  low  for  furnace  operations,  like  that  of  the  puddling  furnace,  both 
manganese  and  iron  sulphides  are  readily  oxidized  by  the  higher  oxides  of 


CHEMISTRY  OF  THE  PROCESS  237 


these  elements,  such  as  Fe2O3,  forming  oxides  of  the  metals  and  SC>2  which 
escapes,  as  a  gas,  from  the  furnace.  At  the  higher  temperatures  of  the  open 
hearth  there  are  a  number  of  factors  that  operate  against  the  elimination 
of  the  sulphur  in  this  way,  among  which  may  be  mentioned  an  increased 
tendency  of  iron  to  combine  with  sulphur,  an  increase  in  the  reducing  power 
of  the  molten  iron,  the  fact  that  CO  gas  is  capable  of  reducing  SC>2,  and  the 
probability  that  there  is  little  Fe2Os  available  to  do  the  work.  Fe3O4 
may  replace  Fe2Os  in  the  oxidation,  but  it  is  very  improbable  that  FeO 
is  capable  of  producing  the  same  result.  Unlike  the  sulphates  of  the  heavy 
metals,  the  sulphates  of  the  alkaline  earths,  such  as  calcium  sulphate,  are 
not  decomposed  by  heat  alone,  at  least  not  by  any  temperature  attainable 
in  the  open  hearth.  Therefore,  once  the  sulphur  is  oxidized  and  thus  com- 
bined with  lime,  there  is  some  chance  of  its  being  held  by  the  slag.  How- 
ever, iron  is  capable  of  decomposing  the  sulphate  of  lime,  thus,  CaSO4+ 
4  Fe=FeS+CaO+3  FeO,  in  which  case  the  iron  sulphide  dissolves  in  the 
iron.  As  evidence  that  such  a  reaction  may  take  place,  several  instances 
may  be  cited  in  which  steel  has  been  ruined,  for  the  order  it  was  intended, 
through  charging  old  boiler  tubes,  containing  much  boiler  scale,  with  the 
scrap.  The  presence  of  oxides  in  the  slag  tend  to  hold  this  reaction  in 
check,  so  that  it  takes  place  to  an  appreciable  degree  only  when  the  slag 
is  burdened  with  an  excessive  amount  of  this  sulphate,  and  even  then  it 
can  occur  only  at  the  surfaces  of  contact  between  metal  and  slag. 

Sulphur  From  the  Fuel:  Another  source  from  which  sulphur  may  be 
imparted  to  the  metal  is  the  fuel.  That  fuel  carrying  compounds  of  sulphur 
may  be  responsible  for  a  portion  of  the  sulphur  content  of  steel  is  a  well  known 
fact,  but  through  what  reactions  the  transfer  is  brought  about  does  not  appear 
to  have  been  satisfactorily  explained.  Now,  it  has  been  established  by  J. 
B.  Ferguson,  writing  in  the  Journal  of  the  American  Chemical  Society,  Novem-' 
ber,  1918,  that  "CO  andSO2  react  between  1000  °C.  and  1200  °C.  to  form  CO2 
and  sulphur  vapor  and  traces  of  carbon  oxysulfide  in  mixtures  rich  in  CO." 
In  the  early  stages  of  an  open  hearth  heat,  just  after  the  addition  of  the  molten 
pig  of  the  charge,  these  conditions  as  to  temperature  and  presence  of  CO  gas 
prevail  at  the  surface  of  the  charge,  and  any  sulphur  vapor  that  may  be  formed 
as  above  will  readily  be  taken  up  by  the  exposed  molten  or  solid  metal  of  the 
charge,  forming  iron  sulfide.  If  there  is  taken  into  account  the  action  of  man- 
ganese toward  sulphur,  there  are,  then,  two  agencies  that  act  feebly  to  eliminate 
sulphur  from  the  metal,  and  two  that  are  active,  also  feebly,  in  returning 
it,  or  of  introducing  it.  The  stability  of  the  calcium  sulphate,  however, 
acts  as  a  guard  against  the  introduction  of  the  element,  except  under  some 
such  unusual  condition  as  that  noted  above. 

Phosphorus  and  Its  Oxides:  This  element  is  very  easily  oxidized, 
when  in  the  free  state,  by  oxygen  alone,  and  forms  several  oxides,  of  which 
only  one,  phosphorus  pentoxide,  P2O5,  need  be  considered  here,  because  it 
is  the  only  one  formed  under  the  conditions  prevailing  in  the  open  hearth. 
Like  sulphur,  phosphorus  occurs  in  the  metal  as  a  definite  compound,  iron 


238  OPEN  HEARTH  PROCESS 


phosphide,  Fes?,  and  like  silica,  the  oxide,  P2O5,  is  an  acid,  which  must 
be  neutralized  as  soon  as  it  is  formed.  The  reaction  by  which  it  is  removed 
from  the  metal  is,  therefore,  probably  most  nearly  correctly  represented 
by  the  following  expression:  2  Fe3P+8  FeO=(FeO)3.P2O5+ll  Fe.  Silica 
has  the  power  of  replacing  ^2^5  in  the  ferrous  phosphate,  thus  exposing  the 
latter  oxide  to  reduction,  so  that  phosphorus  is  never  permanently  removed 
from  the  metal  until  the  silicon  has  been  practically  all  eliminated.  This 
power  of  silica  also  accounts  in  part  for  the  fact  that  phosphorus  is  not 
eliminated  by  any  of  the  acid  processes  for  making  steel,  for  the  proportion 
of  this  compound  in  the  slag  effectually  prevents  the  formation  of  the 
phosphate.  In  the  basic  process  the  abundance  of  bases  present  in  the 
slag  is  more  than  sufficient  to  satisfy  the  silica,  so  that  the  ferrous  phosphate 
is  not  only  permitted  to  form,  but  on  reaching  the  slag  it  is  converted 
into  a  much  more  stable  calcium  phosphate,  probably  the  tri-calcium 
phosphate,  (CaO)3*P2O5.  Even  this  salt  is,  relatively  speaking,  easily 
reduced.  Phosphorus,  therefore,  is  held  by  the  slag  only  so  long  as  the 
latter  is  maintained  strongly  basic  and  at  least  moderately  oxidizing. 

Carbon  and  Its  Oxides:  Owing  to  the  peculiar  chemical  and  physical 
properties  of  carbon  and  its  oxides,  the  elimination  of  this  element  gives 
rise  to  phenomena  distinctively  different  from  those  of  the  elements  just 
reviewed.  In  that  review  it  was  pointed  out  that  the  oxidation  of  those 
elements  gives  compounds  which  are  liquids  under  the  conditions  of  the 
open  hearth,  that  is,  they  are  slag  forming  elements.  But  the  oxidation 
of  the  carbon,  which  is  represented  by  the  reactions  C+FeO— CO4-Fe  and 
Fe3C+FeO=CO+4  Fe,  gives  rise  to  the  gas  carbon  monoxide,  and,  owing 
to  the  conditions  under  which  it  takes  place,  produces  the  phenomenon 
known  as  the  ore  boil.  Thus,  since  the  carbon,  either  as  a  compound  or 
as  an  element,  is  dissolved  in  the  metal,  and  the  iron  oxides,  in  the  slag, 
the  region  of  greatest  activity,  at  the  beginning  of  the  oxidation,  is  located 
near  the  surface  of  contact  between  the  two  liquids.  The  generation  of 
the  carbon  monoxide  here  gives  rise  to  innumerable  tiny  bubbles  of  the 
gas,  which  immediately  rise  into  the  slag;  but  owing  to  the  small  size  of 
the  former  and  the  viscosity  of  the  latter,  their  immediate  escape  is 
hindered,  so  that  they  find  their  way  to  the  surface  very  slowly.  They 
thus  collect  in  the  slag,  increasing  its  volume  and  imparting  to  it  the  appear- 
ance of  foam.  In  the  course  of  time,  the  highly  oxidizing  condition  of  the 
bath  has  disappeared  with  the  consequent  lowering  of  the  carbon  content, 
and  both  oxide  and  carbon  are  so  reduced  in  amount  that  the  oxidation 
no  longer  takes  place  rapidly  and  near  the  surface  of  the  metal;  so  the  slag 
loses  the  foamy  appearance.  Indeed,  as  the  silicon,  manganese,  phosphorus 
and  part  of  the  carbon  have  been  oxidized,  the  bath  of  metal  is  becoming 
depleted  of  its  reducing  agents,  so  that  more  and  more  ferrous  oxide  pene- 
trates or  is  dissolved  by  the  metal,  which  fact,  together  with  the  decom- 
position of  the  limestone,  gives  rise  to  the  formation  of  large  bodies,  or 
bubbles,  of  carbon  monoxide  deep  down  in  or  near  the  bottom  of  the  layer 


CHEMISTRY  OF  THE  PROCESS  239 


of  metal.  These  bubbles  rise  through  the  metal  rapidly,  so  that  when  they 
strike  the  slag,  it  is  not  given  time  to  part,  but  is  lifted  into  the  atmosphere 
of  the  furnace  and  thrown  to  one  side. 

The  Action  of  the  Limestone:  It  is  interesting  to  note  to  what 
extent  the  decomposition  of  the  limestone  on  the  bottom  of  the  furnace 
may  contribute  to  this  action  and  to  the  elimination  of  the  carbon.  The 
reaction  representing  this  decomposition  is  CaCO3=CaO-{-CO2.  Now,  the 
carbon  dioxide  gas  is  no  sooner  set  free  than  it  is  attacked  by  iron,  thus: 
CO2+Fe=FeO+CO.  The  FeO  is  then  available  for  the  oxidation  of  the 
carbon  in  the  metal,  thus:  FeO+C=Fe+CO.  By  combining  these  two 
reactions  it  will  be  observed  that,  from  each  and  every  volume  of  carbon 
dioxide,  CC>2,  liberated,  two  volumes  of  carbon  monoxide,  CO,  result.  The 
CO  derived  from  the  decomposition  of  the  limestone,  as  well  as  that  from 
the  action  of  dissolved  FeO,  escapes  to  the  surface  as  just  described.  Any 
ore  that  might  have  remained  at  the  bottom  of  the  furnace  up  to  this  period 
of  the  carbon  elimination  would  also  contribute  to  the  violence  of  this 
action.  At  the  surface  of  the  slag  the  carbon  monoxide  discharged  by 
the  bath  may  burn  to  carbon  dioxide,  which  escapes  with  the  products  of 
combustion  from  the  flame.  The  boiling  of  the  bath  thus  plays  a  very 
important  part  in  the  process.  When  the  slag  is  thrown  aside  by  the  bubbles 
of  gas,  t  he  metal  is  exposed  to  the  action  of  the  flame,  and  though  this 
exposure  is  but  momentary  in  each  instance,  the  large  number  of  such 
exposures  result  in  the  formation  of  a  considerable  quantity  of  ferrous  oxide 
in  this  way.  But  the  greatest  benefits  are  derived  from  the  agitation  of 
the  bath.  It  is  easily  seen  how  this  agitation  must  result  in  a  mixing  of 
the  slag  and  metal,  thus  increasing  the  area  of  the  reacting  surfaces,  while 
the  stirring  effect  on  the  metal  itself  should  not  be  overlooked.  Thus,  the 
metal  lying  near  the  bottom,  which  is  the  coldest  and  most  impure,  is 
brought  upward  to  be  heated  and  exposed  to  the  oxidizing  influences,  so 
that  both  the  temperature  and  composition  of  the  bath  are  kept  more  uniform 
than  they  could  otherwise  be  maintained. 

Effect  of  Carbon  Elimination  on  Slag  Composition:  In  conclusion, 
it  should  be  pointed  out  that  the  effect  of  the  carbon  elimination  upon  the 
slag  is  to  reduce  its  content  of  iron  oxides.  By  proper  regulation  of  the 
conditions  this  reduction  of  the  oxides  in  the  slag  may  be  brought  down  to 
the  point  where  the  total  iron  content  of  the  slag  will  be  about  10%  of  its 
weight,  of  which  iron  about  7/10,  or  70%,  will  be  in  the  ferrous  condition. 
The  advantages  of  adding  ore  to  the  charge,  as  may  now  be  readily  seen, 
are  to  increase  the  speed  of  the  purification  and  to  decrease  the  waste 
of  metal,  which  is  more  expensive  than  ore. 

The  Order  of  Elimination  of  the  elements  just  reviewed,  with  the 
exception  of  sulphur,  is  the  same  as  the  order  in  which  they  have  been 
discussed,  namely,  silicon  and  manganese,  phosphorus,  and  lastly  carbon. 
Some  reasons  why  the  first  three  elements  are  eliminated  in  this  order 
have  been  mentioned  under  their  respective  headings,  but  nothing  has  been 


240  OPEN  HEARTH  PROCESS 

mentioned  that  would  appear  to  cause  carbon,  which  is  capable,  under 
proper  conditions,  of  reducing  the  compounds  of  all  these  elements,  to  be 
the  last  element  oxidized  in  the  open  hearth.  The  explanation  for  this 
difference  in  the  chemical  properties  of  carbon  is  connected  with  the  fact 
that  its  reducing  power  increases  as  the  temperature  rises.  Again,  chemical 
action,  when  it  occurs  independently  of  external  influences,  always  takes 
place  in  the  direction  that  will  liberate  the  most  energy,  as  was  pointed 
out  in  Chapters  I  and  VII.  The  oxidation  of  silicon,  manganese,  and 
phosphorus  and  the  neutralization  of  the  resulting  oxides  are  exothermic 
reactions,  whereas  the  carbon  reaction  is  endothermic.  The  elimination 
of  the  four  impurities  thus  takes  place  in  accordance  with  the  amounts  of 
heat  evolved  or  absorbed.  As  an  example  of  these  laws,  let  the  elimination 
of  silicon  and  carbon  be  compared.  These  reactions  with  the  heat,  or 
energy,  values  involved,  are  as  indicated  in  the  following  expressions: 

(l)Si+2FeO=    Si  O2+2Fe (+64600  cal.) 

—2(65700)  +196000=64600 
(2)  C+FeO=CG+Fe  (—36540  cal.) 
—65700+29160=— 36540 

Reaction  (1)  shows  that  in  the  oxidation  of  one  gram  of  silicon  approxi- 
mately 2307  cals.  (64,600H-28=2,307)  of  heat  are  evolved,  while  in  the 
oxidation  of  one  gram  carbon,  as  shown  by  reaction  (2)  3, 045  cal.  of  heat  are 
absorbed.  If  now  the  reduction  of  silica  and  carbon  monoxide  by  carbon 
and  silicon,  respectively,  be  compared  as  in  reaction  (3)  and  (4),  it  will 
be  seen  that,  whereas  carbon  absorbs  heat  in  reducing  silica,  silicon  reducing 
CO,  liberates  heat.  (3)  SiO2+C=2  CO+Si(— 137640  cal.)  (4)  2  CO+Si= 

—196000  +2x29160  —2x29160 

Si(>2+C(+137640  cal.)  It  is  evident,  then,  that  the  oxidation  of  the  carbon 
+196000 

cannot  be  complete  until  the  silicon  has  been  eliminated.  At  high  tem- 
peratures, such  as  may  prevail  in  parts  of  the  blast  furnace  or  in  the  electric 
furnace,  for  example,  the  heat  absorbed  in  reaction  (3)  is  supplied  from 
external  sources,  which  addition  of  energy  causes  the  carbon  to  act  as  a 
reducing  agent  toward  the  silica.  What  has  been  said  with  respect  to 
silicon  also  holds  true  in  the  case  of  manganese  and  phosphorus.  In  the 
basic  open  hearth  the  temperature  rises  gradually,  so  that  carbon  has  no 
opportunity  to  act  as  a  reducing  agent  toward  oxides  of  these  elements. 

Factors  Opposing  this  Order  of  Elimination:  What  has  been 
written  above  should  not  be  taken  to  mean  that  each  element  is  completely 
and  successively  eliminated  in  the  order  mentioned,  for  there  are  other 
laws,  such  as  the  law  of  mass  action,  for  example,  that  operate  to  bring 
about  the  elimination  of  these  elements  simultaneously.  The  oxidation  of 
the  carbon,  for  example,  evidently  begins  shortly  after  the  hot  metal  has 


CHEMISTRY  OF  THE  PROCESS  241 

been  added  to  the  charge,  and  certainly  before  the  manganese  and  phos- 
phorus have  been  entirely  disposed  of.  What  is  implied  is  that  the  elimi- 
nation of  each  element  in  the  order  named  is  successively  in  the  ascendency 
until  eventually  only  the  carbon,  in  part,  remains  to  be  oxidized.  When 
this  element  has  been  practically  all  removed,  the  bath  of  metal  no  longer 
contains  reducing  agents  and  is  subject  to  over-oxidation  by  absorption  of 
ferrous  oxide,  FeO,  up  to  the  point  of  saturation  in  equilibrium  with  the 
slag.  This  fact  explains  why  it  is  undesirable  to  make  ore  additions  to 
the  slag  just  previous  to  tapping,  and  also  why  the  heat,  unless  deoxidizing 
agents  are  added  to  the  bath,  should  not  be  held  in  the  furnace  for  more  than  a 
few  minutes  after  the  carbon  content  has  been  lowered  to  .10%,  which  figure 
is  within  about  .03%  of  the  minimum  carbon  content  for  this  process. 


Resume:  All  that  should  now  be  required  in  order  that  the  chemistry 
of  this  process  may  be  fixed  clearly  in  mind,  is  a  rapid  review  of  the  subject 
matter  included  under  the  heading  of  Operation  of  the  Furnace,  which  will 
now  appear  in  a  new  light.  To  begin  this  review,  picture  a  furnace  in  the 
course  of  operation  which  has  received  its  charge  of  solid  materials  for, 
say,  a  Monell  heat.  The  first  effect  on  this  charge  will  be  an  increase  of 
temperature.  The  limestone,  ore  and  the  lining  of  the  furnace  all  being 
basic  in  character,  will  remain  inactive  at  first,  and  continue  so  until  they 
will  have  absorbed  sufficient  heat  to  raise  their  temperature  to  the  point 
where  decomposition  begins.  For  limestone  this  temperature  is  about 
850°  C.,  while  the  ore  will  not  give  up  its  oxygen  until  its  temperature  is 
near  the  fusion  point,  about  1400°  C.,  unless  it  comes  in  contact  with  reducing 
agents.  The  absorption  of  heat  by  the  ore  and  stone  is  hindered  by  the 
scrap  charged  upon  them.  This  material,  being  a  good  conductor  of  heat 
and  exposed  to  the  flame,  absorbs  heat  very  rapidly,  and  as  soon  as  the 
temperature  rises  above  the  thermo-critical  range,  oxidation  of  the  iron 
begins,  this  giving  rise  to  the  formation  of  scale.  The  melting  point  of 
this  scale  is  so  near  that  of  the  metal,  that  it  may  remain  on  the  surface 
until  the  metal  itself  begins  to  melt.  It  is  understood,  of  course,  that  the 
impurities  contained  in  the  scrap  will  suffer  oxidation  with  the  iron.  These 
fluids  will  trickle  down  over  the  colder  material  beneath  and  will  eventually 
reach  the  ore  on  the  bottom  of  the  furnace.  Here,  together  with  additional 
oxide  derived  from  the  ore  and  some  silica,  lime,  etc.,  collected  from  various 
sources,  this  molten  scale  will  go  to  make  up  the  first  slag.  This  slag,  poor 
in  silica,  but  exceedingly  rich  in  iron  oxides,  especially  ferrous  oxide,  and 
containing  some  lime  also,  is  well  constituted  for  the  work  it  has  to  do; 
and  with  the  addition  of  the  hot  metal,  the  purification  may  begin  at  once. 
Thus,  the  silicon,  manganese  and  phosphorus  will  have  been  practically 
eliminated  from  the  metal  within  two  hours  after  the  molten  metal  is 
charged.  The  extent  and  character  of  the  purification  of  the  metal  at 
the  time  of  the  run  off  with  the  resulting  change  in  the  composition  of 
the  slag  are  indicated  in  the  following  table  of  analyses. 


242 


THE  OPEN  HEARTH  PROCESS 


Table  34.     Analyses  of  Hot  Metal  and  Slag  Before  Charging   and  at 
Time  of  First  Run=off. 


ANALYSIS  OF  METAL. 
Per  cent,  of 

PARTIAL  ANALYSIS  OF  SLAG. 
Per  cent,  of 

Heat 

No. 

C 

Mn 

P 

S 

Si 

SiOa 

FeO 

FesOs 

MnO 

CaO 

MgO 

PaOs 

80s 

S 

1 

1 
2 
3 

4 

5 

Pig  Iron  Before 
Charging  

At  Time  of  Run  Off.. 

3.85 
2.39 
2.41 
2.45 

2.80 

3.74 

1.55 
.05 
.02 
.02 
.01 

.01 

.198 
.022 
.053 
.068 
.015 

.043 

.035 
.040 
.060 
.049 
.043 

.037 

1.04 
.04 

4.72 
19.19 
25.18 
23.68 
15.74 

19.30 

66.67 
32.86 
17.39 
26.33 
45.16 

42.59 

not 
det'md 

5.22 
4.07 
7.10 
7.50 

5.91 

1.30 
12.97 
13.16 
13.54 
6.19 

6.84 

18.00 
18.38 
17.88 
12.22 
11.34 

12.41 

2.00 
6.11 
12.18 
10.14 
5.23 

3.84 

.78 
1.11 

.090 
.090 
.165 

.182 

.029 
.027 
.037 

.063 

Briquettes  Instead  of 
Ore  Used  

From  this  point  the  reader  should  be  able  to  continue  this  review 
through  the  oxidation  of  the  carbon  unaided,  and  in  doing  so,  he  will  have 
fixed  in  mind  the  chemistry  of  the  process  much  more  firmly  than  if  he 
but  read  the  inadequately  expressed  thoughts  of  another.  As  a  further  aid, 
what  is  said  in  Chapter  V  concerning  final  open  hearth  slags  should  be 
referred  to. 


ELECTRIC  PROCESS  243 


CHAPTER  IX. 

MANUFACTURE  OF  STEEL  IN  ELECTRIC  FURNACES. 

SECTION   I. 

INTRODUCTORY. 

The  Plan  of  Study:  To  understand  the  process  of  manufacturing 
steel  by  means  of  the  electric  furnace  requires  some  knowledge  of  electrical 
phenomena.  To  the  question  as  to  what  electricity  is,  no  very  satisfactory 
definition  can  be  given.  The  modern  idea  is,  that  it  is  the  fundamental 
of  which  all  matter  is  composed,  because  there  is  evidence  to  indicate  that 
electrons  are  but  corpuscles  of  negative  electricity,  which,  together  with 
nuclei  of  positive  electricity,  go  to  form  atoms.  That  it  is  either  a  form 
of  energy  or  an  agent  for  transmitting  energy  is  evident,  and  the  various 
phenomena  attending  it  may  be  due  to  the  production  of  strained  conditions 
in  the  Ether,  somewhat  similar  to  the  effect  of  heat  upon  water  in  the 
generation  of  steam.  However,  the  question  is  of  no  importance  except  to 
distinguish  the  thing  from  the  phenomena  produced  by  it,  which  are  of 
great  importance.  To  those  who  have  not  been  able  to  devote  much  time 
or  study  to  the  subject,  these  phenomena  appear  as  deep  mysteries  and  are 
difficult  to  understand.  This  study  may,  therefore,  be  appropriately  intro- 
duced by  a  brief  explanation,  presented  in  as  simple  a  manner  as  possible, 
of  such  of  the  phenomena  and  laws  of  electricity  as  apply  to  the  subject 
of  steel  manufacture  by  this  method.  To  be  of  the  greatest  help  to  those 
unfamiliar  with  electricity,  it  is  necessary  to  begin  with  the  fundamentals 
and  build  up  such  a  structure  as  the  limits  of  space  and  time  will  permit. 

Force,  Work,  Energy  and  Potential:  In  the  industrial  world  the 
fundamental  or  prime  factor  is  work.  It  is  defined  as  the  operation  of 
overcoming  resistance  through  space,  or  as  the  production  of  effects  upon 
bodies.  That  which  is  the  immediate  cause  of  these  effects  is  force,  which 
is  more  accurately  defined  as  that  which  causes,  or  tends  to  cause,  a  change, 
in  the  motion  of  a  body,  in  either  velocity  or  direction.  Thus,  a  column 
may  exert  a  powerful  force  in  supporting  part  of  a  building,  because  it 
tends  to  change  the  direction  of  motion  the  overburden  would  have  if  free 
to  fall;  but  it  does  no  work,  because  no  effect  is  produced.  Force  is  measured 
by  the  product  of  the  mass  of  the  body  it  acts  upon  and  the  acceleration 
(rate  of  change  of  motion)  it  produces.  In  the  centimeter-gram-second 
(C.  G.  S.)  system  the  absolute  unit  of  measurement  is  the  dyne,  which 
is  the  force  required  to  produce  an  acceleration  of  one  centimeter  per.  sec. 
per.  sec.  in  a  mass  of  one  gram.  On  the  foot-pound-second  (F.  P.  S.)  system, 
the  unit  is  the  pound,  which  is  the  force  exerted  by  gravity  on  a  definite 


244  ELECTRIC  PROCESS 


mass  of  matter.  A  similar  unit  on  the  centimeter-gram-second  system  is 
the  kilogram,  which  is  the  force  exerted  by  gravity  on  a  mass  of  one  kilogram. 
That  which  imparts  to  a  body  the  ability  to  do  work  is  energy.  Both  are, 
therefore,  measured  by  the  same  unit.  In  the  foot-pound-second 
system  this  unit  is  the  foot-pound,  or  the  work  done  by  a  force  of  one 
pound  acting  through  a  distance  of  one  foot.  In  the  centimeter-gram-second 
system  a  large  unit  is  called  the  kilogram-meter,  while  a  small  unit,  one  dyne 
acting  throu  gh  a  distance  of  one  centimeter,  is  called  the  erg.  The  j  ou  le,equal 
to  10,000,000  ergs,  is  a  more  practical  unit.  Thus,  if  a  weight  of  10  Ibs.  is 
lifted  against  gravity  to  a  distance  of  5  ft.,  50  foot-pounds  of  work  has  been 
done  on  that  body,  and  50  foot-pounds  of  energy  was  expended,  and  the 
same  amount  of  energy  is  stored  up  in  the  body  raised  in  the  form  of 
potential  energy,  which  imparts  to  this  body  the  ability  to  do  work.  In 
practice  the  body  lifted  would  be  said  to  have  its  potential  raised,  or  a 
difference  in  potential  has  been  effected  between  this  position  of  the  body 
and  (the  same  body  in)  its  former  position. 

Power:  It  will  be  noticed  that  work  is  independent  of  time.  The 
time  rate  of  doing  work  is  called  power.  In  the  foot-pound-second  system 
the  unit  is  the  horse  power,  (h.  p.),  which  equals  33,000  foot-pounds  in  one 
minute  or  550  foot-pounds  in  one  second.  It  is  based  on  experiments  in  which 
it  was  found  that  the  work  an  average  draft  horse  can  perform  continually 
without  over-exertion  is  equivalent  to  lifting  a  weight  of  150  pounds  vertically 
while  travelling  at  the  rate  of  2.5  miles  per  hour.  In  the  centimeter-gram- 
second  system  the  unit  is  the  watt,  which  is  that  power  that  will  do  one 
joule  of  work  in  one  second.  The  large  unit  equals  1000  watts  and  is 
called  kilowatt.  This  unit  is  employed  in  electrical  work.  1  kilowatt= 
1.34  h.  p.,  or  1  h.  p., =746  watts=.746 kilowatts.  Since  energy  is  conserved, 
power  can  be  supplied  only  by  creating  a  difference  in  potential. 

Transmission  of  Energy:  In  the  mechanical  world  it  is  often  desir- 
able, for  economical  reasons,  to  create  this  potential  difference  at  some 
central  point,  known  as  the  power  station,  from  which  the  power  may  be 
distributed  by  proper  means  to  various  other  points  and  applied  as  required. 
For  the  transmission  of  energy  there  are  four  agencies,  namely,  gases,  such 
as  steam;  fluids,  such  as  water;  electricity;  and  the  Ether.  In  certain 
respects  the  characteristics  exhibited  by  any  one  of  these  agencies  in  use 
is  similar  to  each  of  the  others.  In  the  first  case  the  difference  in  potential 
is  maintained  by  making  use  of  the  potential,  or  chemical  energy,  of  fuels 
to  generate  steam,  which  may  be  conducted  through  pipes  to  impart  motion 
to  engines  and  do  work  upon  matter,  or  to  give  up  its  energy  as  heat. 
Similarly,  water  may  be  made  to  transmit  energy  by  causing  it  to  flow 
through  pipes  from  high  levels  to  lower  ones.  Somewhat  analogous  to  the 
flow  of  the  water,  is  the  passage  of  the  electric  current  along  a  wire. 
In  each  case  means  must  be  taken  to  maintain  the  flow  by  keeping  up  a 
difference  in  potential.  In  the  case  of  water,  a  pump  could  be  inserted  in 
a  circuit  for  returning  the  water  to  the  higher  level  as  rapidly  as  it  flows 


ELECTRICAL  UNITS 


245 


downward.  In  practice  a  pump  would  be  impracticable,  but  the  sun 
accomplishes  the  same  thing  by  vaporizing  water  so  that  it  rises  into  the 
atmosphere  to  fall  again  as  rain,  and  thus  complete  the  circuit.  In  electric 
circuits  this  difference  in  potential  is  maintained  by  means  of  the  electric 
battery,  the  static  machine,  or  the  dynamo,  the  last  of  which  will  be  briefly 
described  later.  The  close  similarity  between  these  two  cases  will  be 
readily  observed  by  a  study  of  the  following  table  of  analogues,  in  which 
the  water  is  assumed  to  be  flowing  through  a  horizontal  pipe  at  the  point 
of  examination: 

Table  35.     Hydraulic — Electric  Analogues. 


Functions  of 

the  Currents 

Hydraulic 

Electromagnetic 

Hydraulic 

Electric 

Units 

Units 

Pressure  
Quantity  

E.  M.  F.  or 

Voltage  

Pressure    per    sq. 
in.  or  Head  in 
feet  
Pound  

Volt. 
Coulomb. 

Rate  of  flow  
Friction.  . 

Amperage  
Resistance  to  con- 

Pounds per  second 
Loss  in  Head, 

Coulombs  per  sec. 
or  Amperes. 

Work  

duction  
Electrical  Energy 

No  unit  
Foot-pounds.  . 

Ohm. 
Joule. 

Rate  of  Work 

Wattage  . 

Horse-power  or 

Watt  or 

watt  

Volt  —  Ampere  . 

One  important  point  of  difference  between  the  transmission  of  water 
and  electric  current  is  evident;  namely,  that  whereas  water  passes  through 
a  hollow  tube,  electrifications  pass  along  solid  bodies,  usually  wires.  It 
is  also  common  knowledge  that  electrifications  will  pass  along  some  sub- 
stances very  easily  and  only  with  difficulty,  or  not  at  all,  along  others. 
No  substance  is  so  good  a  conductor  as  not  to  offer  some  resistance  to  the 
transfer.  Substances  that  offer  little  resistance  are  called  conductors; 
those  in  which  the  resistance  is  great,  non-conductors  or  insulators.  In 
the  following  table,  the  substances  named  are  arranged  in  the  order  of 
their  conductivities: 

Table  36.    Relative  Conductivity  of  Various  Substances. 


Conductors 

Metals 

Graphite 

Acids 


Salt  water 
Linen 
Cotton 
Dry  wood 
Paper 


Silk 

India  rubber 

Porcelain 

Air 

Glass 


Sealing-wax 
Rubber 
Vulcanite 
Insulators 


246  ELECTRIC  PROCESS 


Electromotive  Force  (E.  M.  F.):  While  a  definition  of  the  various 
electrical  units  at  this  time  would  be  out  of  place,  occasion  should  be  made 
to  explain  electrical  pressures.  Just  as  hydraulic  pressure  might  be  called 
water-moving  force,  so  pressure  produced  electrically  is  called  electromo- 
tive force  (e.  m.  f.).  As  indicated  above,  the  unit  of  measurement  for 
electromotive  force  is  the  volt,  which  is  also  the  unit  for  measuring  difference 
in  potential.  In  practice  electromotive  force  and  difference  in  potential 
are  different  things.  Electromotive  force  refers  to  the  total  electrical 
pressure  existing  in  a  circuit,  whereas  difference  in  potential  is  merely  the 
difference  in  electrical  pressure  between  two  points  on  the  circuit. 

SECTION   II. 

THE    DEVELOPMENT   OF  ELECTROMOTIVE   FORCES — OR 

"GENERATION  OF  CURRENT."1 

Methods  for  Setting  up  Electric  Currents:  As  already  indicated  the 
difference  in  potential  between  two  points,  which  is  necessary  to  produce  an 
electric  current,  may  be  created  by  different  methods,  of  which  the  most 
common  and  useful  are  the  following:  1.  By  friction,  as  in  the  electro- 
phorus,  or  electrostatic  machine.  2.  By  chemical  action,  such  as  that 
which  takes  place  in  the  electric  battery,  or  voltaic  cell.  3.  By  electro- 
magnetic induction,  as  in  the  dynamo.  In  all  these  cases,  energy  must  be 
expended  to  produce  the  difference  in  potential,  and  the  points  of  different 
potential  must  be  connected  by  a  conductor.  Electrostatic  machines,  while 
they  produce  a  high  electromotive  force,  generate  only  a  small  quantity  of 
electricity  in  a  given  time.  Current  produced  in  this  way  has,  therefore, 
a  very  limited  use.  In  the  voltaic  cell  these  conditions  of  current  are 
reversed,  the  amperage  being  high  and  the  voltage  low.  The  dynamo  can 
be  made  to  give  current  high  in  both  voltage  and  amperage.  It  is,  there- 
fore, the  most  useful  of  all  electrical  machines,  and  is  the  source  from 
which  the  current  required  by  the  electric  steel  furnace  is  obtained.  This 
being  the  case,  a  discussion  of  the  principles  involved  in  the  working  of  this 
machine  should  be  both  interesting  and  instructive.  To  an  observer  not 
familiar  with  the  subjects  of  magnetism  and  electricity,  the  dynamo  appears 
as  a  machine  for  changing  motion  into  electrical  energy,  and,  in  a  way, 
this  idea  is  correct.  But  the  generation  of  the  current  is  not  due  to  motion 
alone.  Other  phenomena,  known  as  magnetism  and  induction,  are  involved, 
and  to  understand  the  generation  of  the  current  these  must  be  studied  first. 

Magnetism :  The  attractive  force  of  magnets  upon  iron  is  well  known. 
Upon  investigation,  it  is  found  that  every  magnet  possesses  two  poles, 
designated  as  North  and  South,  N.  and  S.,  or  +  and  — ,from  which  lines 
of  force  issue,  and  that  these  lines  of  force  protrude  into  the  space  surround- 
ing the  magnet  and  extend  from  pole  to  pole.  In  studying  the  action  of  one 
magnet  upon  another,  the  following  laws  are  observed:  1.  Like  magnetic 

*For  a  fuller  study  of  the  generation,  transmission  and  utilization  of  the  elec- 
tric current  see  the  standard  text  books  on  Physics,  also  Practical  Electricity  by 
Terrel  Croft  and  Applied  Electricity  for  Practical  Men  by  Arthur  J.  Rowland. 
Published  by  McGraw-Hill  Book  Company,  Inc.,  New  York. 


MAGNETISM 


247 


poles  repel  one  another;  while  unlike  poles  attract  one  another.  2.  Lines 
of  force  having  the  same  direction,  i.  e.,  issuing  from  like  poles,  repel  each 
other;  those  of  opposite  direction  attract.  All  these  facts  are  illustrated 
in  the  accompanying  figures,  which  are  diagrams  made  from  photographs 
of  actual  conditions. 


Fro.  28.  Diagrams  of  Sections  through  the  space  surrounding  magnets  showing  lines 
of  force  between  like  (A)  and  unlike  (B)  poles.  Anyone  may  study  these  lines  of 
force  for  himself  by  securing  two  bar  magnets,  some  iron  filings,  and  a  piece  of 
paper.  The  paper  is  laid  upon  the  magnets  and  the  filings  are  sprinkled  upon  it. 
The  filings  are  thus  magnetized  and  arrange  themselves  in  lines  or  curves  corre- 
sponding to  the  lines  of  force. 

Magnets  and  Magnetic  Substances:  Magnets  may  be  natural  or 
artificial.  Most  magnets  are  artificial  and  may  consist  of  straight  bars  or 
rods  as  shown  in  the  figure,  or  be  curved,  as  is  the  case  with  horse  shoe 
magnets.  These  magnets  may  be  either  permanent  or  temporary.  Per- 
manent magnets  are  made  of  hard  steel  and  retain  their  magnetism 
indefinitely,  whereas  temporary  magnets  are  made  of  soft  steel  and  are 
magnets  only  so  long  as  they  are  under  the  influence  of  a  magnetizing  force. 
The  space  surrounding  the  magnet  through  which  lines  of  force  pass  is 
called  the  magnetic  field,  and  the  number  of  lines  is  referred  to  as  the 
magnetic  flux.  Substances  that  are  attracted  by  a  magnet  or  are  mag- 
netized when  placed  in  a  magnetic  field  are  called  magnetic  substances. 
While  it  can  be  shown  that  most  substances  are  affected  by  magnetism, 
iron,  its  alloys,  and  one  oxide,  Fe3C>4,  are  the  only  substances  available  for 
use.  These  lines  of  force  cannot  be  insulated,  for  they  pass  through  all 


248 


ELECTRIC  PROCESS 


substances,  but  by  the  use  of  a  permeable  substance,  like  very  soft  steel 
or  iron,  they  may  be  deflected  from  their  course  and  concentrated  in  the 
mass  of  iron  as  shown  in  A  of  Fig.  29. 


FIG.  29.  Magnetic  Permeability  and  Induction. 

A.  The  soft  iron  washer  encloses  a  space  through  which  there  are  no  lines  of  force. 
B.  Cut  in  two,  the  washer  becomes  a  magnet  by  induction. 


Magnetic  Fields  and  Electric  Currents:  These  magnetic  lines  of 
force  are  closely  associated  with  the  electric  current,  for  it  is  easily  shown 
that  every  current  bearing  conductor  is  surrounded  by  a  magnetic  field, 
the  lines  of  force  in  which  form  circles  concentric  with  the  conductor. 
These  lines  of  force  have  a  definite  direction  as  in  the  case  of  ordinary 
magnets,  and  this  direction  bears  a  fixed  relation  to  the  direction  of  the 
current,  as  shown  in  A  of  Fig.  30.  This  fact  is  made  use  of  in  producing 
the  electromagnet,  by  coiling  the  conductor,  properly  insulated,  about  a 
core  of  soft  iron,  as  shown  in  C  of  Fig.  30.  Such  a  coil  is  known  as  a  helix 
or  solenoid,  and  has  poles  similar  to  magnets.  The  various  relations 
between  flow  of  current,  lines  of  force,  and  poles  of  the  helix  are  shown 
in  the  figure.  The  wide  application  of  these  facts  cannot  be  discussed  here, 
except  in  so  far  as  they  have  to  do  with  the  development  of  an  electromotive 
force,  or,  as  this  is  more  commonly  referred  to,  the  generation  of  the  electric 
current.  In  connection  with  the  generation  of  currents,  this  question  might 
arise:  If  a  current  produces  a  magnetic  field  about  a  conductor,  will  the 
production  of  a  magnetic  field  about  a  conductor  result  in  a  current?  This 
question  is  now  to  be  answered  by  a  brief  study  of  electromagnetic  induction. 


ELECTROMAGNETISM 


Electromagnetic  Induction :  The  easiest  way  of  bringing  about  such 
a  condition  as  noted  in  the  preceding  paragraph  is  described  in  the  following 
experiment:  If  a  coil  of  many  turns  of  fine  copper  wire  is  connected  to  a 
delicate  galvanometer  and  one  end  of  a  bar  magnet  is  thrust  into  it,  the 
galvanometer  needle  will  be  deflected,  showing  that  a  current  is  set  up  in 


Battery 


FIG.  30.  Magnetic  Fields  About  Current  Bearing  Conductors. 

A.  Lines  of  force  about  a  wire  carrying  a  direct  current. 

B.  Lines  of  force  in  the  current  bearing  helix. 

C.  The  Electro-magnet.     The  lines  of  force  pass  into  the   soft   steel 

bar,  which  becomes  a  magnet  by  induction. 

the  coil  As  long  as  the  magnet  remains  stationary,  no  current  will  pass. 
Upon  suddenly  withdrawing  the  magnet,  however,  a  current  will  again  pass, 
but  the  direction  of  this  second  current  is  opposite  to  that  of  the  first.  If 
these  operations  be  repeated  with  the  other  pole  of  the  magnet,  similar 
currents  will  be  induced,  but  in  directions  opposite  to  those  obtained  when 
the  first  pole  is  used.  Instead  of  moving  the  magnet,  the  coil  can  be  moved 
with  a  like  result,  and  in  place  of  the  magnet  a  solenoid  can  be  substituted. 
In  the  last  case  it  may  not  be  necessary  to  move  either  the  solenoid  or  the 


250 


ELECTRIC  PROCESS 


coil,  as  current  can  be  set  up  in  the  coil  by  breaking  the  circuit  or  other- 
wise  interrupting  the  current  in  the  solenoid.  From  these  facts  it  would  seem 
that  the  sole  cause  of  the  current  is  the  change  in  magnetic  flux.  Further 
study  of  these  phenomena  reveals  the  fact  that  the  current  induced  is  affect- 
ed by  the  speed  with  which  the  magnet  may  be  inserted  and  withdrawn,  and 
the  number  of  wires  in  the  coil.  In  the  case  of  the  solenoid  a  third  factor 
is  introduced,  as  the  current  carried  by  the  solenoid  itself  affects  the 
induced  current.  Furthermore,  no  current  is  set  up  in  the  coil  unless  the 
motion  is  such  that  its  wires  cut  the  lines  of  force  produced  by  the  exciting 
elements:  no  current  is  generated  if  the  conductor  moves  along  the  lines 
of  force.  All  these  facts  are  summed  up  in  the  following  laws: 

Laws  of  Electromagnetic  Induction:  1.  Any  change  in  the  number 
of  lines  of  force  passing  through  a  closed  conducting  circuit  induces  a  current 
in  that  circuit.  (2)  The  direction  of  the  induced  current  is  always  such 
that  its  magnetic  field  opposes  the  motion  which  produces  it  (Lenz's  law). 
(3)  The  electromotive  force  of  the  induced  current  is  directly  proportional 
to  the  rate  at  which  the  number  of  lines  of  force  are  increased  or  decreased, 
or,  the  rate  at  which  the  lines  of  force  are  cut. 

The  Dynamo:  Coming  now  to  the  practical  application  of  these 
principles,  it  is  found  that,  of  the  many  electrical  appliances  depending 
upon  them,  the  dynamo  and  the  transformer  are  of  chief  interest  in  a  study 
of  the  electric  furnace.  The  dynamo  is  designed  to  convert  mechanical 
energy  into  electrical  energy.  The  steam  engine,  for  example,  does  work 
on  a  dynamo,  and  the  dynamo  produces  an  electric  current.  This  current 
contains  all  the  energy  that  was  received  from  the  engine  except  a  small 
percentage  which  was  lost  in  heat  and  friction.  There  are  three  essential 
parts  of  a  dynamo:  1st.,  the  field  magnets;  2d.,  the  armature;  3d.,  the 
collecting  brushes.  The  magnets  are  used  to  create  a  strong  magnetic 
field  between  the  two  poles,  that  is,  a  field  in  which  there  are  many  lines 
of  force. 

Revolving  Loop  • 
of  Copper  Wire 


Magnet"^ 


Brushes 


FIG.  31.  Diagram  Illustrating  Essential  Parts  and  Principle   of  the  Dynamo, 
a.  Direction  in  which  loop  revolves.        b  and  b'.  Direction  of  current  through  loop, 
c.   Directi  on  of  lines  of  force,  dandd'.  Direction  of  current  in  external  part  of  the  circuit. 


KINDS  OF  CURRENT  251 


Hence,  in  all  large  dynamos  electromagnets  are  used.  The  armature 
consists  of  coils  of  wire  wrapped  around  a  soft  iron  core;  it  is  mounted  so 
as  to  rotate  in  the  magnetic  field  and  cut  lines  of  force.  The  current  is 
thus  generated  in  the  manner  described  under  induction.  The  essential 
parts  of  a  dynamo  are  shown  in  the  diagram  of  Fig.  31,  which  illustrates 
the  arrangement  for  a  drum  wound  armature.  The  north-seeking  pole  of 
the  field  magnet  is  marked  N;  the  south-seeking  pole,  S.  The  armature 
is  here  a  single  loop  of  wire.  The  ends  of  the  loop  are  connected  to  rings 
which  rest  on  collecting  brushes.  When  the  loop  is  rotated,  it  cuts  the 
lines  of  force,  causing  a  current  to  flow  out  to  the  brushes  and  through  the 
external  part  of  the  circuit.  The  direction  of  this  flow  bears  a  fixed 
relation  to  the  lines  of  force  as  explained  under  induction  and  as  shown  in 
the  figure.  In  practice  the  following  rule  is  employed  to  determine  the 
direction  of  the  current  in  the  armature.  Extend  the  thumb,  first  finger, 
and  middle  finger  of  the  right  hand  in  such  a  manner  that  each  will  be  at 
right  angles  to  the  other  two.  Place  the  hand  in  such  a  position  that  the 
first  finger  will  point  in  the  direction  of  the  lines  of  force  (N.  to  S.)  and 
the  thumb  in  the  direction  in  which  the  conductor  moves.  The  middle 
finger  will  then  point  in  the  direction  in  which  the  current  flows. 


SECTION   III. 

KINDS    OF   CURRENT. 

Alternating  Current:  The  current  produced  in  the  dynamo 
armature  is  not  a  constant  one  and  travelling  in  one  direction,  such  as  is 
obtained  by  means  of  batteries,  but  is  an  alternating  one,  as  a  further  study 
of  Fig.  31  will  show.  Let  the  coil  be  rotated  as  indicated  by  the  curved 
arrow  above  it.  While  the  side  at  b  is  moving  downward  in  front  of  the 
pole  N.,  the  side  at  b'  will  be  moving  upward  in  front  of  the  pole  S.  An 
application  of  the  law  for  direction  shows  that  the  currents  thus  induced 
by  the  two  branches  of  the  coil  cutting  lines  of  force  will  flow  in  opposite 
directions  in  relation  to  each  other,  but  in  the  same  direction  from  end 
to  end  around  the  coil.  This  current  continues  as  long  as  b  and  b'  are 
moving  in  the  same  direction  across  the  lines  of  force — that  is,  during 
one-half  of  one  complete  rotation.  Then,  as  the  rotation  continues,  the 
sides  of  the  coil  cut  the  lines  in  an  opposite  direction,  and  the  current  is 
completely  reversed.  Each  time  the  coil  is  turned  half  way  around,  the 
direction  of  the  current  is  changed.  Each  end  of  the  ceil  is  attached  to 
a  ring.  The  rings  are  attached  to  the  axis  of  the  coil  and  rotate  with  it. 
Brushes  slide  upon  the  rings  and  conduct  the  current  out  upon  the  line  of 
the  external  circuit.  The  line  current  is  thus  changed  in  direction  twice 
during  each  complete  rotation  of  the  coil  or  armature.  Each  change  in 
direction  is  called  an  alternation.  Two  alternations  constitute  a  cycle — 
that  is,  a  circle  or  series  of  changes  which  will  be  repeated  in  the  next  cycle. 
The  time  required  for  one  cycle  is  the  period.  The  number  of  cycles  in 


252 


ELECTRIC  PROCESS 


one  second  is  the  frequency.  The  frequency  is  one-half  the  number  of 
alternations  in  one  second.  In  modern  forms  of  alternators  the  frequency 
is  seldom  more  than  60  nor  less  than  25  cycles  per  second.  To  produce 
60  cycles  in  a  second  with  a 
machine  like  that  shown  in  Fig.  31, 
the  armature  would  have  to  make 
3600  rotations  in  one  minute.  To 
avoid  such  high  speed,  a  number 
of  pole  pieces  are  arranged  in  a 
circle  around  the  armature,  making 
what  is  called  a  multipolar  ma- 
chine. These  poles  are  wound  so 
that  north  and  south-seeking  poles 
alternate  in  position.  A  cycle  is 
then  produced  in  the  circuit  by  the 
passage  of  any  two  adjacent  poles. 
If  there  are  ten  poles,  there  are 
five  cycles  during  one  rotation  of 
the  armature.  A  current  of  25 
cycles  per  second  would  mean  50 
alternations  per  second  or  3000  per 
minute;  on  a  two  pole  machine  it 
would  require  1500  r.  p.  m.;  on  a 
10  pole,  300  r.  p.  m.  The  latter 
is  about  as  Iowa  speed  as  a  machine 
can  be  operated  upon  economically. 
These  are  some  of  the  reasons 
why  it  is  not  practical  to  operate 
alternators  on  cycles  over  60  nor 
under  25. 


Graphic    Representation    of 
Alternating  Current:  The  surges 
of   the  current  are    approximately 
harmonic,  hence  the  electromotive 
force  may  be  represented    by  the  .- 
sine    curve,  as   shown  in   Fig.  32.  i 
This    figure    shows  one    complete  ! 
wave  or  cycle,  as  taking  place  in  ^  ; 
second  of  time,  and  going  from  zero  1 
through  a  positive  maximum  and  " 
back  to  zero,  where  it  continues  to 
a   negative    maximum    to    return 


again  to  zero,  thus  completing  a  cycle.  The  different  stages  of  vibration 
represented  in  the  graph  are  spoken  of  as  phases.  Thus  b  and  b'  are  in 
the  same  phase,  but  b  and  h'  are  in  opposite  phases,  etc. 


KINDS  OF  CURRENTS 


253 


Direct  Currents :  While  all  dynamos  produce  alternating  current  in  the 
armature,  this  current  may  be  changed  to  a  direct  one  by  means  of  a  com- 
mutator properly  connected  to  the  armature.  How  this  is  done  can  be 
understood  by  a  study  of  the  accompanying  figure. 


Legend: 

a.  a.  Armature  Loops 
b,b,b,b.  Brushes 
c,c.  Commutator 
Direction  of  Rotation 
"         "    Current 
"         "    Magnetic 
Lines  of  Force 


FIG.  33.  Diagram  Illustrating  how  Current  is  Rectified  by  means  of  a  Commutator 
For  reasons  to  be  given  later,  direct  currents  are  not  used  in  furnaces  for  refining 
iron  and  steel. 


Polyphase  Currents:  In  order  to  increase  the  efficiency  and  output 
of  alternators,  recourse  is  had  to  polyphase  current.  These  currents 
are  the  result  of  attempts  to  put  to  economic  use  the  interpolar  space,  or 
surface  of  armature  core,  which  is  only  partly  filled  in  by  conductors  in 
single  phase  machines.  In  any  given  machine  of  this  kind,  which 'involves 
certain  given  mechanical  and  magnetic  losses,  approximately  only  half  of  this 
space  is  utilized.  This  waste  of  space  and  consequent  inefficiency  can  be 
removed  by  utilizing  the  space  devoted  to  the  core  of  the  coil  for  the  winding 
of  other  coils,  and  thus  form  a  second  armature  of  an  equal  number  of  coils 
overlapping  the  former  and  utilizing  the  same  magnetic  field.  In  this 
second  armature  the  phase  of  the  current  would  be  a  quarter  period,  90 
degrees,  ahead  or  behind  that  of  the  first,  and  so  would  require  four  wires  to 
carry  the  currents  to  and  from  the  generator.  The  output  of  the  machine, 
however,  has  been  doubled.  Further  attempts  to  increase  output  have 
resulted  in  electrical  engineers  going  even  further  and  constructing  triple 
armatures,  in  which  the  phase  of  the  currents  generated  differ  by  equal 
intervals  of  %  of  a  period,  or  60  degrees.  But  this  scheme  then  leads  to 
considerable  elaboration,  if  the  circuits  be  totally  independent  with  six 
conductors,  and  very  little  advantage  could  be  shown  to  exist  over  the 
two-phase  with  four  lines.  However,  in  cases  where  it  is  possible  to  arrange 
that  the  demand  in  the  different  circuits  be  approximately  equal  and  evenly 
distributed,  the  three  phase  system  can  be  worked  out  to  great  advantage 
by  using  only  three  conductors.  By  referring  to  the  accompanying  diagrams 
(Figs.  34  and  35)  it  will  be  seen  that,  at  any  moment  whatever,  the  sum  of 
the  electromotive  forces  in  the  three  circuits  is  zero.  In  other  words,  the 
electromotive  force  on  one  line  is  always  equal  to  that  on  the  other  two, 


254 


ELECTRIC  PROCESS 


and  opposite  in  kind.     Thus,  at  any  instant  one  of  the  three  wires   is  to  be 
looked  upon  as  the  return  wire  for  the  other  two. 


FIG.    34.  Diagrams   Illustrating    The   Methods  of   Generating  the    Three  Kinds  of 
Alternating  Current. 

The  Two  Schemes  of  Wiring  for  Three  Phase  Current:  The  coils 
of  the  three  phase  current  alternator,  as  well  as  those  of  the  apparatus 
that  is  to  consume  the  power,  may  be  connected  in  two  different  ways 
with  each  other  as  shown  in  the  following  diagrams.  In  these  diagrams 
the  three  phase  generator  is  considered  as  a  compound  machine  made  up 
of  three  separate  machines.  In  such  a  machine,  the  separate  units  may 


KINDS  OF  CURRENTS 


255 


be  wired  independently  as  shown  in  Fig.  35A.  Instead  of  three  return  wires, 
one  common  return  wire  may  be  employed,  as  shown  by  the  dotted  line  R 
in  the  figure.  But  it  is  found  that,  with  balanced  loads  on  each  system,  R  is 
a  neutral  line,  that  is,  no  current  flows  through  it;  consequently,  it  is  omitted 
as  in  the  figure.  The  points  m  and  n  are  therefore  called  neutral  points. 
The  form  of  this  diagram  suggests  the  name  for  the  scheme,  which  is  known 
as  the  star,  or  Y,  connection.  In  the  other  schemes  the  coils  of  the  dynamo 
are  connected  in  a  series,  and  the  power  is  led  off  through  mains  connected 
to  points  in  the  connecting  lines.  Fig.  35B  shows  diagrams  intended  to 
illustrate  the  scheme  for  this  connection.  On  account  of  the  similarity 
to  the  Greek  letter  A,  this  scheme  is  known  as  the  delta  connection. 
It  is  also  called  the  V  and  mesh  connections.  It  will  be  observed  that  the 
windings  of  the  delta  connection  form  a  closed  circuit,  and  the  generator  there- 
fore appears  to  be  short  circuited.  However,  such  is  not  the  case,  because, 
owing  to  the  fact  that  the  currents  generated  by  the  three  windings  differ 
in  phase  by  120°,  as  shown  in  Fig.  34C,  the  resultant  of  the  three  voltages 
is  at  every  instant  zero,  hence  no  current  can  flow  by  way  of  the  short  circuit. 
With  this  plan  of  connections  the  load  may  be  balanced  or  unbalanced  as  each 
coil  or  set  of  windings  supplies  its  own  load. 


As  generated 
A.  Diagram  of  Star  (or  Y)  Connections. 

L -"  '  


As  generated 


58  Volts 


As  consumed 


As  consumed 


B.  Diagram  of  Delta  (Mesh  or  V)  Connections. 

Fio.  35     Diagrams  Illustrating  the    Two    Methods   of    Winding   and    Wiring    for 
Three- Phase  Currents. 

These  connections  are  of  importance  in  understanding  how  the  power 
of  3-phase  currents  is  transmitted.     They  also  affect  the  voltage  employed, 


256  ELECTRIC  PROCESS 

the  relations  being  as  shown  in  the  preceding  diagrams.  The  Duquesne 
furnace,  for  example,  operates  on  104  volts  with  star  connections  and  180 
volts  with  the  delta.  This  care  in  explaining  three  phase  current  has  been 
taken,  because  it  is  the  most  common  kind  of  current  and  is  used  in  the 
Heroult  furnace,  the  details  of  which  will  be  explained  later. 


SECTION   IV. 

TRANSMISSION  OF  THE  CURRENT. 

Ohm's  Law:  With  this  brief  explanation  of  the  generation  of  the 
current,  it  will  be  well  to  turn  next  to  the  problem  connected  with  its  trans- 
mission. Here,  also,  it  is  necessary  to  begin  with  the  simplest  essentials. 
The  most  fundamental  idea  in  this  connection  can  be  briefly  stated  in  the 
form  of  a  law,  known  as  Ohm's  law.  This  law  states  that  the  strength 
of  current  passing  along  a  conductor  varies  directly  as  the  electromotive 
force,  or  drop  in  potential,  and  inversely  as  the  resistance.  This  law  is 
generally  put  in  the  form  of  a  formula,  thus: 

E  Electromotive  Force 

or  Current=— — ; 

R  Resistance 

In  place  of  these  letters  the  units  which  are  used  in  measuring  the  quantities 
they  represent  may  be  substituted,  thus: 

V  Volts 

A=—      .  or          Amperes=; 


O  Ohm's 

By  the  use  of  this  formula  any  one  of  the  three  quantities  may  be  found, 
provided  the  other  two  are  given.  It  may  be  applied  to  an  entire  circuit 
or  to  a  part  of  a  circuit. 

Resistance  of  Conductors :  Referring  now  to  resistance  of  conductors, 
it  will  be  recalled  that,  as  previously  stated,  all  conductors  offer  resistance 
to  the  passage  of  the  current.  This  resistance  can  be  calculated  by  applying 
the  following  law,  which  has  been  developed  by  many  experiments.  It  is 
stated  as  follows: — The  resistance  to  the  flow  of  an  electric  current  along 
a  given  conductor  at  a  given  temperature  varies  directly  as  the  length 
and  inversely  as  the  area  of  its  section,  and  is  different  for  different 

substances.     As  a  formula,  the  law  is  expressed  thus:    R=  — g- where  R= 

resistance,  l=length,  d2=square  of  the  diameter,  which  is  directly  pro- 
portioned to  the  area,  or  the  area  itself,  and  K=specific  resistance  of  the 
substance.  In  the  foot-pound-second  system,  l=length  in  feet,  and  d= 
diameter  in  mils,  or  thousandths  of  an  inch.  A  circular  mil  is  the  area 
of  a  circle  one  mil  in  diameter.  So  if  the  diameter  of  a  wire  is  expressed 


TRANSMISSION  OF  CURRENT  257 

in  mils,  d2=the  area  in  circular  mils.  The  circular  mil  is  not  to  be  con- 
fused with  the  square  mil  which  is  the  area  of  a  square  having  sides  1/1000 
inch  long.  The  area  of  a  circle  in  square  mils,  the  diameter  of  which  is 

expressed  in  mils  = .     In  this  connection  the  following  formulas  may  be 

found  of  assistance: 

1.     sq.  mils=cir.  mils X 0.7854  2.     cir.  rnils= 


.0000007854 

In  wire,  a  length  of  one  foot  and  a  diameter  of  one  mil  constitutes  a  mil- 
foot.  The  specific  resistance  of  any  substance  is  the  resistance  of  one  mil- 
foot.  In  the  following  table  are  the  specific  resistances  of  a  few  substances, 
determined  for  this  system,  at  60°  F.  In  the  metric  system,  l=meters, 
d2=sq.  millemeters,  and,  of  course,  K  has  a  numerical  value  different  from 
that  by  the  foot-pound-second  system,  as  shown  in  the  table. 


Table  37.     Specific  Resistance  of  Various  Substances. 

60°  F.  0°  C. 

Foot-Pound-Second  Centimeter-Gram-Second 

(F.  P.  S.)  System  (C.  G.  S.)  System 

Silver 9.53  .017 

Copper 10.35  .018 

Aluminum .03  to  .05 

Gold 13.34  

Zinc 36.46  .06 

Iron .10  to  .12 

Platinum 58.00  .12  to  .16 

Steel 63.00  .10  to  .25 

Molten  Steel 1.66  to  2.2  at  1700°  C. 

Nickel .15 

Lead 127.2  .22 

German  Silver 135.0  .15  to  .36 

Mercury 616.16  .94073 

The  Ohm,  the  unit  of  resistance,  may  now  be  defined.  It  has  been 
established  by  law  to  be  the  resistance  offered  by  a  mercury  column 
1.063  m.  long  of  1.  sq.  mm.  cross  section,  and  at  the  temperature  of  0°  C. 
Originally,  the  length  of  the  mercury  column  was  one  meter. 

Effect  of  Temperature  on  Conductors :  In  connection  with  the  effect 
of  temperature  upon  conductors,  it  should  be  noted  that  there  are  two 
classes  of  substances,  known  as  conductors  of  the  first  class  and  conductors 
of  the  second  class.  In  conductors  of  the  first  class,  which  includes  all 
the  metals,  the  resistance  increases  with  a  rise  in  temperature,  hence  their 
conductivities  decrease.  This  is  shown  in  the  case  of  steel,  which  at  15°  C. 


258 


ELECTRIC  PROCESS 


has  a  specific  resistance  of  only  .10  to  .12,  whereas  at  1700°  the  specific 
resistance  of  the  molten  metal  is  about  1.66.  In  the  case  of  carbon  and 
conductors  of  the  second  class,  these  relations  are  reversed,  so  that  they 
become  better  and  better  conductors  as  their  temperatures  rise.  As  all 
the  refractory  materials  that  go  into  the  construction  of  furnaces  belong 
to  this  class,  this  matter  must  be  carefully  considered  in  building  electric 
furnaces. 

Resistance  in  Series  and  Parallel.  In  the  preceding  paragraph,  only 
single  substances  were  considered  in  the  circuit.  In  the  actual  distribution 
and  use  of  power,  it  is  generally  necessary  to  divide  circuits,  in  which 
divisions  different  materials  or  machines  will  also  make  up  a  part  of  the 
circuit.  This  division  and  connections  can  be  made  in  two  ways,  namely, 
series  and  parallel,  as  shown  in  the  following  diagram  illustrating  two 
methods  of  light  wiring. 

r'  r"         r'" 


L      • 

—  W1  '    '     ^J            ^ 

HI 

A.    Series                                                             r, 

U       :   9r'f^ 

n  -  L 

i      ^^^ 

T 

i 

B.    Parallel 
FIG.  36.  Diagram  Illustrating  Different  Methods  of  Wiring. 


In  Fig.  36  A,  the  resistance  of  the  line  is  r  and  of  each  of  the  lamps  it 
is  r',  then  the  whole  resistance,  R,  is  the  sum  of  these  four,  or 

R=r+r'+r"+r'"  or  R=r+3r'. 

Resistance  of  conductors  connected  in  parallel  is  not  found  so  simply. 
It  is  deducted  from  the  law  of  conductivities,  which  states  that  the  conductiv- 
ity of  a  combination  of  conductors  is  equal  to  the  sum  of  the  conductivities 
of  the  conductors  singly.  Now,  it  is  self  evident  that  the  conductivity  is 

represented  by  -j-     The  resistance  in  the  parallel  connections  above  would 
R. 

then  be  found  by  solving  the  following: 
11111 


This  matter  is  of  importance  in  dealing  with  electric  furnaces,  as  shown 


TRANSMISSION  OF  THE  CURRENT  259 

in  the  following  schematic  diagram  of  the  wiring  of  Heroult  and  Girod 
furnaces,  which  marks  the  chief  difference  between  these  two  furnaces. 


FIG.  37.    Wiring  Diagrams  for  Heroult  and  Girod  Electric  Steel  Furnaces. 

These  diagrams  show  the  Heroult  furnace,  on  the  left,  to  be  connected 
in  series  and  the  Girod  in  parallel. 

Currents  Through  Divided  Circuits :  If  the  different  parts  of  parallel 
connected  conductors  have  equal  resistance,  then  equal  currents  will  flow 
through  these  parts,  as  is  evident  from  Ohm's  law,  thus, 

i=5  r=5 

R  R' 

As  the  current  is  always  delivered  at  a  constant  voltage,  E  is  the  same 
in  both  cases;  hence,  if  R=R',  1=1'.  If  the  resistances  are  not  the  same, 
then  I  would  not  equal  I'.  The  current  flowing  in  each  conductor,  however, 
can  be  found  from  the  following  law:  Currents  which  flow  parallel  to  each 
other  vary  inversely  as  the  resistance  of  the  parallel  connected  conductors. 

Self  Induction,  Impedance,  Power  Factor:  In  dealing  with  alter- 
nating currents,  Ohm's  law  does  not  hold,  for  the  alternations  cause  self- 
inductance  in  the  conductor,  that  is,  they  generate  currents  opposite  in 
direction,  or  kind,  to  that  of  the  main  current;  and  this  inductance  also 
offers  resistance  to  the  current  in  addition  to  that  offered  by  the  conductor. 
The  sum  of  these  two  forces  opposing  the  passage  of  the  current  is  called 
impedance.  If  impedance  be  substituted  for  resistance,  then  Ohm's  law 
holds  for  alternating  currents,  also.  Again,  any  self-induction  in  the  circuit 
causes  a  difference  in  the  phase  between  the  electromotive  force  (voltage) 
and  the  current  (amperage),  so  that  the  latter  either  forges  ahead  of  or 
lags  behind  the  former,  and  the  two  do  not  reach  their  maxima  and 
minima  together.  Consequently,  their  product  at  these  points,  which 
represents  the  energy  available  for  consumption,  is  less  than  the  total 
energy  supplied.  The  ratio,  expressed  in  per  cent.,  between  the  useful 
voltage,  or  that  which  is  required  to  overcome  the  resistance  of  the  con- 
ductors and  to  produce  the  heat  or  do  any  other  work  desired,  and  the 
actual  voltage  required  is  called  the  power  factor. 

Heat  Developed  in  Conductors:  Since  all  conductors  offer  resistance 
to  the  flow  of  the  current,  work  is  done  in  overcoming  this  resistance.  In 
doing  this  work  part  of  the  electrical  energy  is  converted  into  heat  energy, 
just  as  work  is  done  and  heat  developed  in  overcoming  friction.  This  heat 


260  ELECTRIC  PROCESS 


can  be  calculated  by  means  of  Joule's  law,  who  found  from  many  experiments 
that  the  heat  developed  by  a  current  flowing  through  a  conductor  is  directly 
proportional  to  the  time,  to  the  resistance,  and  to  the  square  of  the  current. 
Mathematically  stated,  this  law  is  H=K  I2  RT,  where  H=heat,  I=current, 
R=resistance,  T=time,  and  K=a  constant,  which  Joule  found  to  be  .24. 

Tjl 

Since  from  Ohm's  law,  I=-R  or  E=IR,  H=.24  IET  colories,  when  I  is 

measured  in  ampres,  E  in  volts,  and  T  in  seconds.  The  heat  thus  developed 
is  of  much  importance  in  the  transmission  of  current,  for  if  the  current  be 
sufficiently  large  this  heat  may  raise  the  temperature  enough  to  burn  off 
the  insulation,  or  even  to  melt  the  wire.  This  heating  can  be  overcome 
in  two  ways.  In  the  first  method,  the  diameter  of  the  conductors  could 
be  increased,  which  would  decrease  the  resistance  and  increase  the  carrying 
capacity.  That  this  method  has  its  limits  is  evident,  due  to  the  immense 
weight  of  wire  required  in  some  cases  where  large  current  (amperage)  is 
required,  as  is  the  case  with  electric  furnaces.  The  second  method  is 
applicable  to  alternating  current  only  and  illustrates  both  the  adaptability 
of  the  electric  current  in  general  and  one  advantage  of  alternating  current 
in  particular.  From  Joule's  law  it  is  evident  that  a  current  of  large  voltage 
may  be  carried  on  a  given  wire  provided  the  density,  i.  e.,  amperage  per 
circular  mil  or  square  millimeter  be  kept  low.  Since  power=amperes  X 
volts,  or  for  alternating  current  Power=amperes  X  volts  X  power  factor, 
this  can  be  done  without  reduction  in  power.  But  since  the  furnace  requires 
a  current  of  low  voltage  and  high  amperage,  such  a  current  could  not  be 
used  unless  means  be  taken  to  change  this  high-voltage-low-amperage 
current  into  one  of  low  voltage  and  high  amperage.  How  this  is  done  can 
be  learned  from  the  following  description  of  the  transformer. 

The  Stationary  Transformer:  In  this  instrument  the  desired  trans- 
formation is  effected  by  electro-magnetic  induction  already  discussed.  Of 
course,  then,  only  those  currents  which  are  started  and  stopped  or  increased 
and  decreased  in  rapid  succession,  or  those  in  which  the  direction  of  the 
current  is  changed  many  times  in  a  second,  can  be  transformed.  Such 
current  is  furnished  by  the  alternator.  In  structure  the  transformer  con- 
sists of  two  coils  of  wire  side  by  side  with  a  core  composed  of  many  sheets 
of  soft  iron,  or  a  special  silicon  steel,  packed  together.  The  coils  must,  not 
have  any  metallic  connection  with  any  part  of  the  instrument.  The  first 
coil,  that  through  which  the  main  current  flows,  is  called  the  primary. 
The  second  coil,  or  that  in  which  the  current  is  induced,  is  called  the 
secondary. 

Kinds  of  Stationary  Transformers :  Transformers  are  of  two  kinds — 
step-up  and  step-down.  The  step-up  transformer  increases  the  voltage  and 
decreases  the  amperage.  The  step-down  produces  the  opposite  effect. 
The  change  depends  on  the  relative  number  of  turns  of  wire  in  the  primary 
and  secondary  coils.  If,  for  example,  there  are  100  turns  in  the  primary 
and  1000  turns  in  the  secondary,  the  voltage  will  be  increased  10  times 


UTILIZATION  OF  THE  CURRENT  261 

and  the  amperage  decreased  10  times.  This  is  then  a  step-up  transformer. 
A  step-down  transformer  would  reverse  these  conditions,  throughout.  If 
there  are  the  same  number  of  turns  in  both  coils,  the  current  will  not  be 
changed  except  as  it  may  be  affected  by  the  transformer  efficiency,  which 
should  be  about  98%. 

In  regard  to  the  power  of  the  transformed  current  it  will  be  seen  that, 
since,  whenever  the  transformer  increases  or  decreases  the  voltage,  it 
decreases  or  increases  the  amperage,  the  number  of  watts  will  be  a  constant 
quantity.  Suppose  there  is  a  current  of  100  volts  and  10  amperes  flowing 
through  the  primary.  The  power  is  then  1000  watts.  If  the  transformer 
raises  the  pressure  to  500  volts,  the  strength  of  the  current  will  fall  to  2 
amperes,  but  the  power  of  the  current  is  still  1000  watts.  A  good  trans- 
former gives  out  nearly  all  the  energy  that  is  put  into  it.  A  small 
percentage,  varying  from  2%  to  5%  of  the  voltage,  is  converted  into  heat. 
Usually  this  heat  is  prevented  from  collecting  by  immersing  the  coils 
in  cylindrical  tanks  of  oil  so  constructed  as  to  form  a  circulating  system 
through  pipes  extending  externally  from  the  top  to  the  bottom  of  the 
cylinder.  These  pipes  act  like  a  hot  water  radiator  and  serve  to  keep  the 
whole  bath  and  its  contents  cool.  The  oil  also  serves  as  an  insulator. 
For  steel  furnaces  three  phase  25  cycle  current  is  stepped  down  from  6600 
volts  to  104  on  the  star  connection  or  180  on  the  delta,  the  latter  of  which 
is  seldom  used  on  molten  charges. 

SECTION   V. 
THE  UTILIZATION  OF  THE  CURRENT  IN  ELECTRIC  FURNACES.1 

Effects  Produced  by  Electric  Current:  The  heating  and  magnetic 
effects  of  electric  currents  have  already  been  touched  upon  in  connection 
with  generators,  conductors  and  transformers.  In  order  to  understand 
how  the  electric  current  is  utilized  in  electric  furnaces  it  is  necessary  to 
study  these  and  other  effects  from  a  slightly  different  standpoint;  namely, 
their  effect  upon  the  metallic  charge  in  the  furnace  itself.  In  this  con- 
nection it  may  be  truly  said  that  there  is  but  one  other  effect  produced 
by  the  electric  current,  and  this  effect  is  that  of  bringing  about  chemical 
action.  To  the  question  as  to  what  chemical  action  is  caused  by  the  current 
in  the  bath  of  steel,  the  correct  answer  is:  There  is  none.  As  this  answer 
is  not  in  accord  with  chemical  effects  produced  by  currents  in  other 
metallurgical  operations,  an  explanation  may  be  necessary. 

Chemical  Action  Produced  by  the  Electric  Current:  As  pointed 
out  in  Chapter  I,  electrolysis  is  brought  about  when  electric  currents  are 
passed  through  liquids  under  certain  conditions,  some  well  known  examples 
being  the  dissociation  of  water  and  the  electrolytic  separation  of  aluminum. 
In  these  instances,  however,  it  will  be  observed  that  these  chemical  changes 
occur  only  when  direct  current  flows  through  the  electrolytes.  If  alter- 

!For  a  full  discussion  of  electric  furnaces  See  The  Electric  Furnace  by  Alfred 
Stansfleld,  Published  by  McGraw-Hill  Book  Co.,  Inc.,  New  York,  Electric  Furnaces 
in  Iron  and  Steel  Industry,  by  C.  H.  Vom  Baur,  published  by  John  Wiley  &  Sons, 
New  York,  and  Electric  Furnaces  for  Making  Iron  and  Steel  by  Dorsey  A.  Lyon 
and  Robert  M.  Keeney  Bureau  of  Mines  Bulletin  67. 


262  ELECTRIC  PROCESS 


nating  current  is  used,  then  the  direction  of  the  current  is  constantly 
changing,  and  no  action,  such  as  noted  above,  can  take  place.  Furthermore, 
such  action  would  be  harmful  in  carrying  out  the  electro-thermal  process 
for  steel.  While  it  might  be  possible  with  direct  current  to  purify  the 
metal  by  removing  the  impurities  as  sulphides,  silicides,  and  phosphides, 
there  would  be  no  way  of  controlling  the  process  so  as  to  prevent  the 
reduction  of  lime,  alumina  and  other  oxides,  the  elements  from  which 
would  then  find  their  way  into  the  metallic  bath.  This  reduction  would 
result  in  a  more  impure  product  than  the  raw  material.  Designers  of 
electric  furnaces  for  the  iron  industry  will,  then,  use  alternating  current 
exclusively  and  strive  in  every  way  to  prevent  any  electrolytic  action 
that  might  result  in  electrolysis. 

Electrical  Units  of  Measurements:  The  subject  of  electrolysis  offers 
an  opportunity  to  define  another  of  the  primary  units  used  in  electrical 
measurements.  The  ohm  has  already  been  defined  in  studying  resistance. 
It  now  remains  to  explain  how  the  value  of  the  ampere  is  fixed.  If  a  current 
be  made,  by  means  of  suitable  electrodes,  to  pass  through  a  solution  of 
silver  nitrate,  metallic  silver  will  be  deposited  upon  the  cathode,  or  positive 
pole,  and  the  amount  of  silver  thus  deposited  in  a  given  time  will  be  pro- 
portional to  the  strength  of  the  current.  This  fact  has  been  made  the 
basis  for  fixing  the  value  of  the  ampere.  The  legal  definition  reads  as 
follows: — The  ampere  is  that  current  which  when  passed  through  a  15% 
neutral  solution  of  silver  nitrate  will  deposit  .001118  grams  of  silver  in  one 
second.  The  volt  is  then  legally  defined  as  the  e.  m.  f .  which  will  cause 
a  current  of  one  ampere  to  flow  through  a  resistance  of  one  ohm.  In  fixing 
the  value  of  these  units,  it  was  arranged  so  that  the  power  possessed  by  a 
current  of  one  ampere  under  a  pressure  of  one  volt  is  just  equal  to  one  watt. 
Hence  the  power  of  the  current  in  watts  equals  the  product  of  the  amperage 
and  voltage,  or  W=VXA.  The  watt=hour  is  the  energy  expended  in  one 
hour  when  the  current  is  one  ampere  and  the  voltage,  or  pressure,  one  volt. 
Hence,  60  watts  used  for  one  min.  or  one  watt  used  for  60  min.  will  give  one 
watt  hour.  A  kilo=watt=hour=1000  watt  hours. 

The  Magnetic  Influence  of  the  Current  can  be  of  but  slight 
importance  to  the  metallurgist.  To  the  designer  of  induction  furnaces  they 
are  of  double  importance.  On  account  of  a  certain  motor  effect  which 
they  produce  in  the  molten  metal,  these  forces  cause  what  is  known  as  the 
pinch  effect  which  will  often  break  the  circuit.  In  arc  furnaces  this  motor 
effect  is  present  in  the  immediate  vicinity  of  the  electrodes  causing  a  slight 
motion  of  the  bath. 

Heating  the  Bath :  It  is  to  be  understood,  then,  that  the  only  use  to 
which  the  current  is  applied  in  the  manufacture  of  steel  is  for  the  generation 
of  heat.  It  may  be  well,  therefore,  to  consider  briefly  the  heating  pos- 
sibilities of  the  current  in  connection  with  its  practical  application  to  this 
purpose.  A  little  thought  shows  that  these  possibilities  are  only  three  in 
number,  and  may  be  called  heating  by  direct  resistance,  heating  by  indirect 


METHODS  OF  HEATING 


263 


resistance,  and  heating  by  means  of  radiation  from  an  arc  or  arcs.  A  brief 
discussion  of  the  three  methods,  which  is  also  made  to  serve  as  a  means 
of  describing  the  principles  of  the  many  makes  of  furnaces,  follows: — 

Heating  by  Direct  Resistance:  In  the  method  of  heating  by  direct 
resistance,  the  necessary  heat  to  keep  the  bath  molten  is  produced  by  making 
use  of  the  resistance  of  the  iron  itself.  In  some  respects  this  method  would 
appear  to  offer  some  advantages.  1.  Since  heating  is  effected  by  the 
passage  of  the  current  through  the  liquid  metal,  the  heat  would  be  uniformly 
distributed  throughout  the  mass.  2.  Since  the  heat  generated  is  pro- 
portional to  the  square  of  the  current,  the  amount  of  heat  could  be  regulated 
by  changing  the  resistance  of  the  furnace.  3.  Very  low  voltage  currents 
could  be  used.  But  the  disadvantages  outweigh  the  advantages,  as  will 
be  realized  better  if  they  are  set  along  side  the  advantages,  thus:  1.  As 
the  specific  resistance  of  iron  is  low,  the  high  temperature  required  could 
be  obtained  only  by  the  use  of  very  high  amperage,  which  would  require 
exceedingly  heavy  connections.  2.  This  draw-back  could  be  overcome  by 
increasing  the  length  of  the  bath  and  decreasing  the  cross  sectonal  area; 
but  such  an  arrangement  has  been  found  impracticable  on  account  of  the 
large  area  the  bath  then  covers,  which  results  in  great  heat  losses  and 
precludes  the  easy  change  of  slags  and  handling  of  the  metal.  Hence,  all 
early  attempts  to  employ  direct  resistance  for  heating  proved  failures. 
The  problem  was,  however,  eventually  solved  by  the  invention  of  the  type 
of  furnace  known  as  the  induction  furnace.  In  these  furnaces  the  bath  is 
made  to  form  the  closed  secondary  circuit  of  a  transformer.  This  secondary 
can  then  consist  of  but  one  coil,  as  shown  in  the  following  diagram 
illustrating  the  principle  of  the  induction  furnace  as  invented  by  Colby 
and  Ferranti  and  later  improved  and  adapted  to  the  manufacture  of  steel 
by  Kjellin. 


FIG.  38.   Diagram  Illustrating  Principle  of  Induction  Furnaces. 
Vertical  Section  of  Kjellin  Furnace. 

The  furnace  includes  a  magnetic  circuit,  C,  formed  of  the  usual 
laminated  sheet  iron,  as  in  a  transformer  core.  Electric  energy  is  supplied 
to  a  primary  coil,  D,  while  the  secondary  circuit  is  formed  by  the  ring  of 


264  ELECTRIC  PROCESS 


metal  under  treatment,  contained  in  the  annular  cavity,  A,  forming  the 
crucible.  Now,  when  energy,  in  the  form  of  alternating  current  is  supplied 
to  the  primary  coil,  D,  it  creates  a  varying  magnetic  flux  in  the  laminated 
iron  core,  which  in  turn  induces  a  current  in  the  closed  secondary  circuit 
consisting  of  metal  in  crucible  A.  The  current  density  in  the  secondary 
bears  a  fixed  ratio  to  the  number  of  turns  in  the  primary  coil  D,  so  that 
it  is  possible  by  a  suitable  variation  in  impressed  voltage  to  subject  the 
metal  to  an  extremely  heavy  current  density,  the  heat  being  thus  produced 
in  accordance  with  Joule's  law  simultaneously  throughout  the  entire  mass 
of  the  metallic  bath.  Because  of  the  limited  contact  area  between  slag  and 
metal,  this  type  of  furnace  does  not  readily  lend  itself  to  refining  processes, 
if  the  form  shown  in  the  figure  be  adhered  to.  However,  this  form  was 
later  changed  so  as  to  give  a  central  hearth  of  considerable  size.  Those 
who  have  designed  furnaces  with  the  object  of  improving  the  Kjellin  type 
are  Frick,  Hiorth,  Harden,  Greene,  and  others.  On  account  of  the  low 
specific  resistance  of  iron,  it  is  difficult  to  reach  high  temperatures  in  these 
furnaces.  They  are,  therefore,  not  well  adapted  for  desulphurizing  oper- 
ations in  which  sulphur  is  removed  as  sulphide. 

Indirect  Resistance  Heating  offers  a  second  possibility.  Instead  of 
depending  upon  the  resistance  of  the  bath  alone  to  furnish  the  heat  required, 
some  other  conductor  having  a  high  resistance  might  be  built  into  the 
furnace  in  such  a  way  that  the  heat  generated  in  it  would  be  absorbed  by 
the  material  to  be  heated.  This  is  the  principle  employed  in  many 
laboratory  furnaces  and  in  large  furnaces  for  manufacturing  carborundum. 
But  in  applying  the  method  to  the  manufacture  of  steel  several  insurmount- 
able difficulties  are  presented.  1.  The  resister  can  not  be  composed  of 
carbon  and  in  contact  with  the  metal,  on  account  of  the  absorption  of  this 
element  by  iron.  2.  If  a  suitable  resister  of  another  material  could  be 
found,  it  could  not  be  placed  in  the  bath,  because  it  would  then  be  in 
parallel  with  the  metal.  The  only  way  these  difficulties  can  be  overcome 
is  by  the  use  of  crucibles  to  contain  the  molten  metal.  The  impractic- 
ability of  this  method  is  at  once  evident,  and  furnaces  of  this  type 
designed  for  manufacturing  steel  have  met  with  no  success. 

Arc  Heating:  The  use  of  the  electric  arc,  which  has  been  mentioned 
as  the  third  possibility  for  producing  h,eat,  is  the  simplest  and  the  most 
practical  of  all  and  has  found  the  widest  application  in  the  steel  industry. 
Some  information  as  to  the  nature  of  electric  arcs  should,  therefore,  be 
interesting.  In  beginning,  a  distinction  is  to  be  made  between  electric 
sparks  and  electric  arcs.  While  the  air  is  practically  a  non-conductor,  it 
is  possible  to  create  such  a  high  difference  in  potential  between  two  given 
points  as  to  cause  a  current  to  jump  the  gap  and  establish  equilibrium. 
Such  conditions  occur  in  electrical  storms,  and  lightning  is  an  example  of 
electric  sparks.  In  arcs  the  current  also  passes  through  the  air,  but  it 
will  be  observed  that  a  much  smaller  voltage  is  required  to  form  an  arc 


METHODS  OF  HEATING 


265 


than  is  needed  to  cause  sparks.  The  most  common  example  of  the  arc  is 
the  arc  lamp.  Here  the  arc  is  made  between  two  carbon  electrodes,  but 
in  order  to  strike  an  arc  it  is  necessary  to  bring  the  electrodes  into  contact, 
after  which  a  gap  may  be  gradually  produced  and  the  arc  still  maintained. 
If  the  gap  becomes  too  wide,  however,  the  arc  will  break,  hence  means  of 
regulating  the  distance  between  the  electrodes  must  be  provided. 
Evidently  the  air  is  not  the  conductor  in  arcs  as  in  sparks.  All  these 
phenomena  are  explained  by  assuming  that  some  of  the  electrode  material 
is  vaporized  by  the  heat  of  the  arc,  and  that  these  vapors  serve  as  a  con- 
ductor of  the  current.  Some  idea  of  the  intensity  of  the  heat  of  this  arc, 
which  gives  the  highest  temperatures  yet  attained,  is  to  be  had  from  the 
fact  that  carbon  vaporizes  at  about  3500°  C. 

Methods  of  Applying  the  Arc  in  Arc  Furnaces:  Furnaces  of  this 
type,  then,  depend  almost  wholly  upon  this  high  temperature  of  the  electric 
arc  for  the  heat  required  by  iron  and  steel  baths.  The  following  diagrams 
will  illustrate  the  three  possible  methods  of  applying  the  arc  and  heating 
the  bath. 


^ 


A  B    \^  O 

FIG.   39.    Diagrams  Illustrating  the  Three   Ways  of   Employing  the  Electric  Arc  in 
Steel  Furnaces. 

In  each  of  these  three  cases  the  bath  is  directly  beneath  the  arc  or  arcs 
and  receives  its  heat  mainly  by  radiation.  All  three  possibilities  are 
practical  and  have  been  successfully  applied.  So  these  same  figures  also 
illustrate  the  principles  of  the  three  furnaces  of  the  arc  type. 

The  Stassano  Furnace  is  represented  in  principle  by  Fig.  39A.  The 
distinguishing  feature  of  this  furnace  is  that  the  current  does  not  pass 
through  the  metal  or  slag,  the  heating  being  accomplished  entirely  by 
radiation.  At  first,  Stassano  built  his  furnaces  so  that  they  could  be  rocked 
or  rotated  in  order  to  agitate  the  bath,  but  as  this  feature  did  not  prove 
to  be  of  any  advantage,  it  has  now  been  abandoned.  His  furnaces  are 
now  of  the  tilting  type.  In  practice  three  phase  current  is  generally  used, 
and  the  three  electrodes  enter  the  furnace  at  an  angle  through  the  walls. 
This  plan  has  the  effect  of  placing  a  limit  to  the  size  of  the  furnace,  and 
so  few  of  these  furnaces  with  a  capacity  greater  than  two  tons  have  been 
built.  From  an  electrical  standpoint,  the  furnace  possesses  the  important 
advantage  of  uniform  power  consumption,  thus  avoiding  harmful  fluxuations 
in  current. 


266  ELECTRIC  PROCESS 


Girod  Furnaces:  The  furnace  scheme  shown  in  Fig.  39B  has  been 
developed  by  several  inventors.  It  was  first  successfully  introduced  by 
Girod  for  the  purpose  of  manufacturing  ferro-alloys.  As  shown  in  the 
figure  the  electrodes  are  inserted  in  both  the  top  and  the  bottom  of  the 
furnace,  thereby  connecting  electrodes,  slag  and  molten  metal  in  series. 
Heat  is  thus  produced  in  three  ways,  theoretically  at  least.  By  means 
of  an  arc  at  the  top,  the  greater  portion  of  the  heat  is  generated.  After 
forming  the  arc,  the  current,  in  its  downward  courses,  must  pass  through 
the  layer  of  slag  which,  through  the  heat  of  the  arc  above,  becomes  a  con- 
ductor of  the  second  class,  after  which  the  current  is  conducted  by  the 
molten  metal  to  the  electrodes  at  the  bottom.  In  furnaces  using  a  single 
phase  current,  these  bottom  electrodes  are  four  or  six  in  number  and  are 
equally  spaced  about  the  periphery  of  the  hearth.  In  the  three-phase 
furnaces  there  are  four  upper  electrodes,  two  of  which  must  be  in  parallel, 
and  sixteen  bottom  electrodes.  In  all  cases  the  bottom  electrodes  are  made 
of  steel  and  are  water  cooled.  Other  designers  of  this  type  of  furnace  are 
Keller,  Gronwall,  Nathusius,  Stobie  and  Soderburg. 

The  Principle  of  the  Heroult  Furnace  is  diagrammatically  repre- 
sented in  Fig.  39C.  The  practicability  of  this  principle  is  shown  by  the 
fact  that  the  Heroult  electric  steel  furnace  heads  the  list  of  such  furnaces 
in  use  for  the  manufacture  of  steel.  This  popularity  of  the  Heroult  furnace 
is  due  to  the  fact  that  the  application  of  this  principle  gives  a  furnace  of 
the  greatest  efficiency  combined  with  simplicity  of  construction  and  adapt- 
ability to  many  different  uses.  Details  of  the  construction  of  this  furnace 
will  be  given  later.  At  present  it  is  desired  to  explain  only  the  method 
of  heating.  All  the  electrodes,  as  indicated  by  the  figure,  are  suspended 
from  supports  over  the  roof,  through  which  they  project  to  within  an  inch 
of  the  surface  of  the  slag.  As  the  electrodes  are  so  far  separated  from  each 
other  as  to  prevent  arcs  between  them,  several  resistances  are  introduced 
in  series.  For  example,  let  the  current  be  considered  as  passing  from  A 
to  B.  Then  as  the  current  jumps  the  gap  at  the  foot  of  A,  it  forms  an  arc 
and  passes  into  the  slag,  which  also  has  a  high  resistance.  The  metal, 
having  a  much  lower  resistance,  then  acts  as  a  conductor  for  the  current 
to  the  region  directly  beneath  the  foot  of  electrode  B,  where  the  current 
must  again  pass  through  the  layer  of  slag  and  form  a  second  arc  as  it  jumps 
the  gap  between  slag  and  electrodes.  It  is  evident  that  practically  all 
the  heat  is  formed  by  the  arcs  above  the  slag,  which  acts  as  a  shield  to 
the  metal  and  protects  it  both  from  the  carbon  vapors  thrown  off  from 
the  foot  of  the  electrode  and  from  the  exceedingly  high  temperature  at 
this  point.  Portions  of  this  heat  is  next  imparted  to  the  metal  through 
the  slag,  where  it  may  be  distributed  to  all  parts  of  the  bath  by  conduction 
and  convection.  The  distribution  of  the  heat  is  thought  to  be  aided  by 
a  slight  motor  effect  produced  by  the  current  upon  the  metallic  bath. 
Furnaces  of  this  type  using  single  phase  and  three  phase  current  are  in  use. 
The  only  change  necessary  to  be  made  for  three-phase  current  is  the  insertion 


METALLURGY  267 


of  a  third  electrode.  In  the  development  of  these  furnaces  Heroult  stands 
almost  alone,  though  slight  modifications  have  been  introduced  by  Chaplet 
and  Anderson. 

Some  General  Conclusions:  From  what  has  been  said,  the  following 
facts  are  evident:  1.  That  the  only  part  the  electric  current  plays  in  the 
manufacture  of  steel  is  in  the  production  of  heat.  2.  That  for  producing 
this  heat  there  are  really  but  two  methods  available,  which  has  resulted 
in  two  successful  types  of  furnaces,  namely,  the  induction  type  and  the 
arc  type.  3.  ,  That  from  a  strictly  metallurgical  point  of  view  no  one  of 
these  types  represents  any  marked  advantage  over  the  other,  in  their 
present  high  state  of  development.  This  statement  has  no  relation  to 
claims  of  the  inventors  to  mechanical  and  electrical  points  of  excellence  in 
their  respective  apparatus.  What  advantage  electric  heating  has  over 
other  methods  of  heating  is  now  to  be  discussed. 


SECTION    VI. 

GENERAL  FEATURES   PERTAINING  TO  THE   METALLURGY   OF   STEEL   MADE 
BY  ELECTRO-THERMAL  PROCESSES. 

Advantages  of  Electric  Heating:  To  the  metallurgist  the  electric 
method  of  heating  is  an  ideal  one  for  the  following  reasons,  which  are 
characteristic  of  it:  1.  It  makes  heat  available  very  quickly  and  at  will, 
and  gives  an  unusually  high  temperature.  2.  The  heat  may  be  regulated 
very  nicely,  which  fact  permits  a  charge  to  be  brought  to  any  temperature 
desired  and  to  be  maintained  steadily  at  that  temperature.  3.  Being  the 
cleanest  of  heating  agents,  it  exerts  no  deleterious  effect  upon  the  material 
heated  by  the  evolution  of  harmful  gases.  4.  It  permits  oxidizing 
reducing  or  neutral  operations  to  be  carried  on  at  will.  How  these 
characteristics  of  electric  heating  work  to  the  advantage  of  the  metallurgist 
and  permit  him  to  obtain  a  product  of  the  highest  quality  from  raw 
material  s  of  any  grade  will  be  understood  from  a  study  of  the  topics  to 
follow.  I  n  this  connection  the  chemical  possibilities  are  of  first  importance. 

Refining  Procedure:  The  first  effect  of  the  characteristics  noted 
above  is  to  bring  the  whole  operation  of  refining  metal  under  complete 
control.  The  electric  furnace  is  to  the  metallurgist  what  the  casserole  and 
crucible  are  to  the  chemist.  The  bath,  then,  represents  a  mixture  of  com- 
pounds and  elements,  any  one  of  which  may  be  removed  at  will  by  the 
use  of  the  proper  reagents.  The  condition  may  be  illustrated  by  assuming 
a  furnace  is  to  be  charged  with  the  crudest  of  raw  materials,  cold  pig  iron, 
and  then  showing  how  each  impurity  is  removed.  A  study  of  the  practice 
of  many  plants  shows  that  the  following  procedure  would  be  carried  out: 
After  the  furnace  has  received  its  metallic  charge,  an  oxidizing  flux  of  lime 
and  iron  ore  will  be  added.  A  part  of  this  flux  may  be  charged  ahead  of 
the  metal,  exactly  as  in  the  case  of  the  basic  open  hearth.  After  the  charge 


263  ELECTRIC  PROCESS 


has  been  melted  down,  the  furnace  will  be  tilted  slightly  and  the  slag  which 
has  formed  will  be  carefully  raked  off.  This  addition  of  flux  and  removal 
of  slag  will  be  repeated  as  often  as  may  be  necessary.  A  cleansing  flux 
of  lime  alone  will  then  be  added  and  raked  off.  During  this  period  the 
temperature  should  be  kept  low,  because  phosphorus  is  not  readily  oxidized 
at  high  temperatures  in  the  presence  of  carbon.  The  bath  will  then  be 
covered  with  a  flux  consisting  of  about  5  parts  lime,  1  part  sand  or  other 
form  of  silica,  1  part  fluorspar,  and  M  Par*  of  carbon  in  some  convenient 
form,  such  as  coke,  coke  carbon,  old  electrode,  etc.  The  furnace  will  then 
be  tightly  closed,  and  the  temperature  raised.  In  the  case  of  induction 
furnaces,  it  will  be  found  necessary  after  about  two  hours  to  introduce 
small  portions  of  ferro  silicon,  silico-aluminum,  or  silico-spiegel.  These 
alloys  act  energetically  as  deoxidizers  and  form  a  fluid  slag  which  rises 
to  the  surface.  In  the  Heroult  furnace  carbon  is  the  only  deoxidizer  used. 
After  the  steel  shall  have  been  thoroughly  deoxidized,  any  carburizing 
material  or  alloys  will  be  added  to  bring  the  steel  to  the  desired  com- 
position. When  all  such  material  will  have  been  melted,  and  sufficient 
time  will  have  elapsed  to  permit  them  to  mix  with  the  bath,  the  molten 
steel  will  be  poured  as  a  finished  ingot  product.  This  process  divides 
itself  into  three  distinct  periods,  namely,  an  oxidizing  period,  a  reducing 
period,  and  a  finishing  period,  a  combination  of  conditions  impossible  of 
attainment  in  any  other  process.  The  action  brought  about  during  each 
of  these  periods,  and  the  reasons  for  using  the  reagents  employed  may  now 
be  discussed. 

The  Oxidizing  Period:  It  is  evident  that  the  action  of  the  oxidizing 
flux  must  result  in  the  removal  of  silicon,  manganese  and  phosphorus  in  a 
manner  similar  to  that  of  the  basic  process.  The  important  distinction 
between  open  hearths  and  electric  furnaces  should  be  noted  here.  It  is 
this:  All  the  oxygen  introduced  into  the  electric  furnace  must  be  in  the 
solid  form  as  observed  above,  and  the  amount  can  be  easily  controlled, 
whereas  the  air  admitted  to  open  hearths  furnishes  an  unlimited  amount 
of  oxygen  that  cannot  be  controlled.  Therefore,  since  these  three  elements 
are  easily  oxidized  at  low  temperatures  before  the  carbon,  the  reaction 
may  be  stopped  and  the  bath  held  at  almost  any  carbon  content  desired. 
With  respect  to  phosphorus,  it  has  been  suggested  that  this  element  may 
be  removed  as  phosphide  by  means  of  some  metal,  as  calcium.  While  this 
scheme  is  theoretically  possible,  it  is  still  impracticable,  for  it  is  a  difficult 
thing  to  find  a  metal  that  would  not  alloy  with  iron  in  preference  to  com- 
bining with  phosphorus,  or  whose  phosphides  would  not  so  alloy.  Quite 
frequently,  traces  of  phosphorus  are  found  in  the  reducing  slags,  but  this 
method  of  eliminating  phosphorus,  though  often  attempted,  has  not  been 
made  successful  beyond  the  removal  of  very  small  amounts  and  at  great 
expense.  Hence,  the  only  sure  way  of  removing  this  element  is  to  oxidize 
it  to  phosphoric  acid,  neutralize  with  lime,  and  rake  off  the  resulting  slag. 
In  refining  purer  materials  than  pig  iron,  where  the  removal  of  silicon 


METALLURGY  269 


and  manganese  would  not  be  required,  the  oxidizing  slag  is  called  the 
dephosphorizing  slag.  Considerable  sulphur  is  removed  during  this  period 
in  the  electric  furnace,  especially  where  an  ore  high  in  manganese  is  used, 
whereas  in  the  basic  furnace,  its  removal  is  a  very  uncertain  quantity. 

The  Reducing  Period :  This  is  the  period  in  which  the  electric  furnace 
exhibits  its  great  superiority  over  other  modes  of  refining  iron.  During 
the  period,  the  bath  is  almost  completely  deoxidized  by  means  of  carbon 
alone,  and  the  removal  of  sulphur  is  positive  and  can  be  made  almost  com- 
plete. Its  entire  removal  seems  to  be  impracticable,  as  a  content  of  less 
than  .010%  is  obtained  only  after  prolonged  and  expensive  treatment. 
The  flux  added  is,  therefore,  called  either  the  desulphurizing  or  deoxidizing 
flux. 

Oxygen :    Oxygen  occurs  in  steel  principally  as  FeO,  as  has  been  stated 
in  previous  chapters,  in  which  its  harmful  effects  were  also  dwelt  upon. 
Its  removal  may  be  represented  by  the  following  equation  in  which  M 
may  represent  a  great  number  of  suitable  elements: 
FeO+M=MO+Fe. 

The  deoxidation  may  be  brought  about  in  the  induction  furnace  only 
by  means  of  the  special  deoxidizers  previously  noted,  whereas  in  the  Heroult 
furnace  carbon  alone  may  be  employed.  The  use  of  carbon  alone  has  been 
objected  to  because  it  was  argued  that  the  use  of  this  element  would  give 
the  oxide,  CO,  which  is  a  gas,  and  the  formation  of  this  gas  in  the  metal 
is  objectionable.  That  steel  at  high  temperature  either  combines  with  or 
dissolves  this  gas  is  fairly  well  established,  for  by  experiment  it  has  been 
shown  that  a  given  steel  has  a  higher  melting  point  in  an  atmosphere  such 
as  nitrogen  than  it  has  in  an  atmosphere  of  carbon  monoxide.  There  is 
also  good  reason  to  believe  that  this  gas  is  again  liberated  at  certain  tem- 
peratures on  cooling.  If  this  be  true,  then  deoxidizing  with  carbon  may 
give  opportunity  for  formation  of  blow  holes  and  other  defects  in  the  ingots. 
Some  metal,  then,  whose  oxide  is  a  solid  that  will  easily  come  to  the  surface 
as  slag  is  to  be  preferred  for  this  purpose.  This  metal  must  not  be  volatile 
at  high  temperatures  and  must  dissolve  or  alloy  with  the  iron.  The  metals 
that  best  meet  these  requirements  are  the  ferro-alloys  of  manganese,  silicon, 
vanadium,  titanium,  and  metallic  aluminum.  For  many  reasons  manganese, 
silicon  and  aluminum  have  proved  the  most  satisfactory  deoxidizers.  How 
the  carbon,  acting  through  one  or  more  of  these  elements,  may  be  used 
to  accomplish  the  deoxidation  without  injury  to  the  steel  is  well  illustrated 
by  the  practice  at  Duquesne,  to  be  described  later. 

Removal  of  Sulphur:  According  to  the  statements  of  authorities 
upon  the  subject,  sulphur  may  be  removed  in  five  ways:  (1)  As  calcium 
sulphide,  formed  by  the  action  of  lime  and  carbon  on  ferrous  sulphide  at 
the  high  temperature  of  the  arc  furnace;  (2)  As  calcium  sulphide  from 
the  reaction  of  lime,  ferrous  sulphide,  and  calcium  carbide  at  the  higher 


270  ELECTRIC  PROCESS 


temperatures  of  the  arc  furnaces;  (3)  As  calcium  sulphide  through  the 
reaction  of  lime,  ferrous  sulphide,  and  silicon  at  the  lower  slag  temperatures 
of  the  induction  furnace;  (4)  As  calcium  sulphide  through  the  reaction  of 
calcium  fluoride,  ferrous  sulphide,  and  silicon;  (5)  As  iron  sulphide  from 
the  action  of  ferrous  oxide  on  calcium  sulphide.  The  reactions  illustrating 
the  removal  of  sulphur  in  electric  furnaces  are  as  follows: 

(1)  FeS+CaO+C=Fe+CaS+CO.  Occurs  in  arc  furnaces  only. 

(2)  3  FeS+2  CaO+CaC2=3  Fe+3  CaS+2  CO.  in  arc  furnaces  only. 

(3)  2FeS+2CaO+Si=2Fe+2CaS+SiO2.— Used  with  induction  furnaces. 

(4)  2CaF2+2FeS+Si=2CaS+SiF4+2Fe.    May    occur    in  either  induc- 
tion or  arc  furnaces. 

(5)  FeS+CaO  =•=  CaS+FeO.  May  occur  in  arc  furnaces. 

An  inspection  of  these  reactions  shows  that  certain  requirements  must 
be  met  before  the  elimination  of  sulphur  can  be  brought  about.  Thus, 
in  all  cases  a  highly  basic  clag  is  essential,  and  in  no  case  can  desulphur- 
ization  be  effected  before  deoxidation  of  the  metal  and  slag  has  been  accom- 
plished. The  importance  of  the  presence  of  elementary  carbon  or  silicon 
is  evident,  and  both  these  elements  tend  to  react  with  iron  or  manganese 
oxides  rather  than  with  sulphides  and  lime.  Furthermore,  reaction  (5) 
is  reversible,  acting  from  right  to  left  in  the  presence  of  very  slight  oxidizing 
influences.  Because  of  the  relation  in  concentration  maintained  between 
oxides  in  the  metal  and  oxides  in  the  slag,  both  deoxidation  and 
desulphurization  of  the  metal  may  be  brought  about  by  additions 
of  carbon  to  the  slag,  if  the  temperature  is  sufficiently  high.  In 
arc  furnaces  this  method  is  employed  almost  exclusively;  but  induction 
furnaces,  owing  to  their  lower  temperatures,  require  that  desulphuri- 
zation be  effected  by  the  use  of  silicon  as  shown  in  reaction  (3)  and 
(4),  both  of  which  take  place  at  much  lower  temperatures  than  (1)  and 
(2).  In  the  arc  furnace  complete  deoxidation  of  metal  and  slag  is 
recognized  by  the  presence  of  calcium  carbide  in  the  slag. 

The  Finishing  Period:  With  the  dephosphorization  and  subsequent 
deoxidation  of  the  bath,  the  contents  of  the  furnace  may  be  brought  to  a 
neutral  or  slightly  reducing  state,  when-  the  final  additions  may  be  made 
for  finishing  the  steel  to  specifications.  In  order  to  save  time  it  is  a  common 
practice  to  make  some  additions  before  the  desulphurizing  period  com- 
mences, especially  if  the  additions  are  to  be  made  in  large  quantities, 
which  would  chill  the  bath  if  ad'ded  all  at  one  time.  As  the  conditions 
are  reducing  or  neutral,  loss  of  alloying  elements  is  reduced  to  a  minimum, 
and  the  composition  of  the  steel  can  be  controlled  with  precision.  The 


METALLURGY  271 


ability  to  finish  the  steel  in  the  furnace  gives  the  electric  process  another 
advantage  over  any  of  the  older  processes,  also,  as  this  practice  tends  to 
produce  greater  uniformity  in  the  steel. 

Some  Comparisons:  When  deoxidation  of  the  bath  is  complete  the 
contents  of  the  electric  furnace  represents  the  nearest  approach  to  perfect 
chemical  equilibrium  that  has  yet  been  attained  in  other  large  metal- 
lurgical operations.  In  the  converter  and  the  open  hearth  the  metals  are 
subjected  to  the  action  of  air  and  gas;  in  the  crucible  the  metal  takes  up 
carbon  and  silicon;  but  in  the  electric  furnace,  the  action  of  the  metal  on 
the  basic  lining  being  very  slight,  there  is  no  exchange  of  elements 
between  metal  and  slag,  if  traces  of  phosphorus  be  excepted.1  Of  course, 
if  the  dephosphorizing  slag  of  the  oxidizing  period  has  not  been  completely 
removed  before  deoxidization  begins,  some  of  the  phosphorus  compounds 
in  this  slag,  as  well  as  some  in  the  new  slag,  will  be  reduced.  However, 
with  careful  watching,  this  gathering-up  of  phosphorus  by  the  metal  may 
be  entirely  avoided.  As  to  the  relative  merits  of  the  various  types  of 
electric  furnaces,  the  results  obtained  are  about  equal.  However,  it  is 
evident  that  arc  furnaces  are  well  suited  for  reducing  processes,  while 
induction  furnaces  lend  themselves  most  readily  to  oxidizing  purposes. 

Fluxing  Materials  used  in  the  electric  furnace  should  be  as  pure  as 
possible  and  free  from  injurious  amounts  of  sulphur  or  phosphorus.  The 
lime  and  fluorspar  should  not  contain  more  than  small  amounts  of  magnesia, 
as  it  makes  the  slag  less  fusible,  which  fact  is  of  great  importance  when 
the  high  basicity  of  the  slags  is  considered.  For  recarburizing,  a  material 
low  in  volatile  matter,  phosphorus,  and  ash  should  be  used.  At  Duquesne, 
anthracite  coal  is  chiefly  employed. 

General  Manufacturing  Practice:  As  indicated  previously,  the 
electric  furnace  may  be  used  to  refine  pig  iron  direct.  But  as  the  major 
portion  of  the  refining  may  be  accomplished  much  more  cheaply  by  one 
of  the  older  methods,  direct  refining  is  not  economically  practiced  at  present. 
Two  courses  of  procedure,  therefore,  remain.  In  the  one,  cold  scrap  iron 
and  steel  of  any  grade  as  to  quality  is  remelted  and  refined  to  produce 
steel  of  high  quality,  while  in  the  other  the  electric  furnace  is  made  part 
of  a  duplexing  process,  whereby  it  is  used  in  conjunction  with  one  of  the 
older  methods  of  refining  to  produce  superrefined  plain  steels  or  alloy 
steels.  This  second  plan  is  the  one  used  by  the  U.  S.  Steel  Corporation. 
At  the  South  Chicago  Works,  the  electric  furnace  is  used  in  conjunction 
with  Bessemer  converters  and  tilting  basic  open  hearth  furnaces,  and  may 
be  used  in  the  finishing  stage  of  either  a  duplex  or  a  triplex  process;  but 
in  either  case  the  steel  finished  in  the  electric  furnace  is  taken  from  the 
open  hearth.  At  Duquesne  the  duplexing  is  in  connection  with  basic  open 
hearths  only,  and  to  furnish  a  concrete  example  of  the  construction  and 
workings  of  the  electric  furnace  this  plant  will  be  described. 

Lyon  and  Keeney,  Electric  Furnaces  for  making  Iron  and  Steel.  Bureau  of 
Mines  Bulletin  67,  Page  125. 


272 


ELECTRIC  PROCESS 


CONSTRUCTION  OF  FURNACE 


273 


274 


ELECTRIC  PROCESS 


FIQ.  42.  Heroult  Electric  Furnace.— Vertical  Section  Through  Tower  and  Furnace. 


DUQUESNE    PLANT  275 


SECTION   VII. 

THE   DUQUESNE   PLANT — FEATURES   PERTAINING  TO   ITS   CONSTRUCTION. 

Equipment:  This  plant  was  completed  early  in  1917,  and  is  located 
at  one  end  of  No.  2  open  hearth  plant  and  in  the  same  building.  The 
special  equipment  of  the  plant  may  be  said  to  consist  of  one  20-ton  Heroult 
tilting  furnace  with  a  transformer  station  and  testing  laboratory,  three 
charging  ladles,  three  pouring  ladles  and  one  traveling  over-head  crane 
for  charging.  Other  equipment  such  as  teeming  cranes,  molds,  cars,  etc. 
are  part  of  the  regular  equipment  of  the  open  hearth  plant.  The  open 
hearth  floors  are  on  two  levels.  The  electric  furnace,  therefore,  standing 
in  line  with  the  open  hearths,  is  elevated  and  so  constructed  that  it  may 
be  charged  from  the  charging  floor  level,  and  tapped  into  the  pouring  ladle 
on  the  ground  floor  thirteen  and  one  half  feet  below  the  charging  level. 
The  transformer  station  is  in  a  brick  building  just  outside  the  open  hearth 
building,  and  about  eighteen  feet  from  the  center  of  the  furnace.  Three 
transformers  are  used,  the  combined  capacity  of  which  is  3500  K.  W.  • 
From  the  transformers  the  current  is  conducted  by  means  of  bus  bars  to 
the  corner  of  the  transformer  house  nearest  the  pouring  side  of  the  furnace. 
Thence  it  is  carried  along  a  large  number  of  heavy  copper  cables  to  the 
furnace.  Wood  bars,  tied  together  like  sections  of  a  picket  fence,  are  used 
to  insulate  the  three  lines  of  cables  from  each  other.  This  arrangement 
furnishes  the  flexible  connections  necessary  to  permit  the  tilting  of  the 
furnace. 

Construction  of  the  Furnace  Shell:  The  furnace  is  circular  in  form, 
and  has  an  outside  diameter  of  approximately  sixteen  feet.  The  shell  is 
made  of  plate  steel  one  inch  thick,  riveted  together.  This  shell  may  be 
considered  as  being  made  in  these  three  parts:  a  channelled  band  for  the  top, 
which  is  removable  and  made  up  of  riveted  plates;  a  side  wall  which  is 
cylindrical  in  shape;  and  a  bottom,  which  is  shaped  somewhat  like  a  hopper. 
The  bottom  and  side  walls  are  riveted  together.  The  shape  of  the  bottom, 
front  to  back,  is  made  to  conform  to  heavy  steel  rockers,  which  rest  on  two 
heavy  castings  that  serve  as  tracks.  The  rockers  and  tracks  are  provided 
with  teeth,  which  mesh  into  each  other  and  thus  prevent  the  furnace  from 
creeping.  The  weight  of  the  furnace  is  supported  by  two  brick  piers  upon 
which  the  tracks,  or  stationary  racks,  are  bedded.  The  tops  of  these  piers 
are  about  five  feet  above  the  ground.  Attached  to  the  rockers  at  the  back 
of  the  furnace,  are  two  crank  shafts  which  in  turn  are  connected  to  two  large 
gear  wheels,  some  five  feet  in  diameter.  These  large  wheels  are  geared  to  a 
140  h.  p.  motor,  which  provides  the  power  for  tilting  the  furnace. 

The  Furnace  Lining  is  made  up  of  three  layers  of  different  materials. 
Next  to  the  shell,  in  the  bottom  and  sides,  is  placed  a  four  and  one  half 
inch  layer  of  fire  brick  laid  edgewise,  and  upon  this  is  laid  a  continuous 
bottom  and  side  wall  of  magnesite  brick.  The  bottom  course  is  nine 


276 


ELECTRIC  PROCESS 


nn       nn        n n 


CONSTRUCTION  OF  FURNACE  277 

inches  thick,  while  the  side  wall  is  thirteen  and  one  half  inches  in  thickness. 
Upon  the  bottom  brick  is  then  sintered  a  layer,  about  thirteen  inches  thick, 
of  dead  burned  magnesite,  which  is  banked  on  the  sides  to  a  safe  distance 
above  the  slag  line. 

The  Roof  is  slightly  dome-shaped,  twelve  inches  in  thickness,  and  made  of 
silica  brick  set  in  on  end.  The  first  course  next  the  channelled  band  is 
made  up  of  large  skew-back  brick.  Thus,  the  roof  is  made  self-supporting. 
As  a  roof  lasts  for  forty  to  seventy  heats  only,  two  extras  are  held  in 
reserve,  ready  to  be  placed  in  case  a  roof  fails  unexpectedly.  In  the  roof, 
three  openings  are  made  for  the  electrodes.  Each  opening  corresponds  to 
one  vertex  of  a  equilateral  triangle,  each  side  of  which  is  about  six  feet  long, 
and  the  center  of  which  is  the  center  of  the  roof.  When  in  place,  the  roof 
sets  so  that  one  vertex  points  toward  the  vertical  guides  for  the 
electrodes,  which  are  on  the  side  of  the  furnace  next  the  transformers. 
While  in  use,  the  top  is  bolted  to  four  brackets  on  the  shell  to  prevent 
the  top  from  slipping  when  the  furnace  is  tilted. 

Controlling  the  Electrodes :  Through  the  three  openings,  noted  above, 
the  electrodes  extend  into  the  furnace  for  a  distance  of  about  four  feet. 
In  order  to  make  the  electrodes  adjustable,  they  are  attached  to  horizontal 
arms  that  project  out  over  the  furnace  from  heavy  vertical  rods  arranged 
to  move  up  and  down  within  vertical  guides.  At  the  top  of  these  rods  and 
properly  insulated  from  them,  the  cables  that  carry  the  current  from  the 
transformer  house  to  the  furnace  are  bolted  and  welded  to  bus  bars  which 
lead  to  the  electrode  holders.  Thus,  the  same  motion  is  imparted  to  both 
the  electrode  holders  and  the  bus  bars.  Each  of  these  rods  is  supported 
and  moved  by  means  of  a  cable  attached  to  its  base  and  leading  over  a 
small  drum  geared  to  a  small  electric  motor.  These  motors  act  through 
automatic  regulators,  which  serve  to  keep  the  end  of  the  electrode  at  the 
proper  arcing  distance  from  the  bath.  By  reversing  a  switch  on  the  switch 
board,  these  motors  may  be  operated  independently  of  the  regulator. 
Furthermore,  the  lifting  device  is  provided  with  a  hand  wheel,  so  as  to  be 
operated  like  a  common  windlass,  whereby  the  electrodes  may  be  regulated 
by  hand. 

The  Electrode  Holders  are  made  in  two  parts,  both  of  which  are  in 
the  form  of  a  two  pronged  fork.  The  upper  part  is  of  copper  and  makes 
the  connection  between  the  electrodes  and  the  bus  bars,  which  are  securely 
bolted  to  it.  The  electrodes  are  held  between  the  two  prongs,  and  since 
the  distance  between  these  prongs  is  about  twenty-four  inches,  contact 
blocks  must  be  used  for  electrodes  less  than  twenty-four  inches  in  diam- 
eter. A  right-and-left  screw  bolt  connects  the  ends  of  the  two  prongs, 
which  enables  the  holder  to  be  opened  and  closed  at  will  and  permits  the 
electrode  to  be  securely  clamped  in  place.  By  this  arrangement,  electrodes 
of  any  size  up  to  twenty-four  inches  diameter  may  be  used.  The  lower 
part  is  made  of  steel  and  acts  as  a  support  for  the  upper  part.  These  two 
parts,  carefully  insulated  from  each  other,  are  held  together  by  means  of 


278 


ELECTRIC  PROCESS 


CONSTRUCTION   OF  FURNACE  279 


insulated  bolts.  Finally,  this  lower  part  is  fastened  to  the  horizontal  arm, 
previously  mentioned,  by  an  insulated  flange  joint.  The  upper  prongs  are 
water  cooled. 

The  Electrodes  used  at  the  plant  may  be  of  graphite,  twelve  inches  in 
diameter,  or  of  amorphous  carbon,  twenty-four  inches  in  diameter,  and  are 
received  in  sections  six  feet  long.  By  means  of  threaded  holes  in  the  ends 
of  the  electrodes  and  headless  screws  of  the  same  material  to  fit,  these 
pieces  may  be  joined  together  so  as  to  give  a  continuous  feed  of  electrodes 
to  the  furnace.  In  this  way  the  great  waste  of  electrodes  from  unused  ends 
is  avoided.  These  threaded  holes  also  serve  a  useful  purpose  in  removing 
the  electrodes  and  changing  them  in  the  holders.  As  the  carbons  are 
constantly  burning  away,  this  change  is  frequently  necessary.  Since  the 
electrodes  are  rather  heavy — a  six  foot  length  of  graphite  electrode  weighs 
426  Ibs. — the  use  of  the  crane  is  made  necessary.  By  means  of  a  linked 
pin  of  steel,  threaded  to  fit  the  hole,  the  electrodes  can  easily  be  handled 
with  the  crane  hook.  Experience  seems  to  indicate  that  graphite  electrodes 
are  best  for  molten  charges  but  that  amorphous  electrodes  are  very  well 
suited  for  use  in  melting  cold  charges.  A  water  cooled  copper  ring  encircles 
each  electrode  at  its  entrance  into  the  furnace. 

Furnace  Openings:  Besides  the  holes  in  the  roof  for  the  three  elec- 
trodes, the  furnace  has  three  openings  in  the  side  wall,  all  located  within 
an  arc  of  180°  on  the  circumference.  One  is  the  tapping  hole,  a  small  opening 
through  which  the  steel  is  poured  into  the  steel  ladle.  This  opening  is 
provided  with  a  spout,  so  constructed  as  to  act  as  a  slag  skimmer  when 
the  furnace  is  tapped.  Opposite  the  tapping  hole  is  the  charging  door, 
through  which  the  molten  metal  from  the  open  hearth  is  charged,  while 
half  way  between  these  two  openings  is  located  a  second  charging  door, 
which  can  be  used  only  for  charging  solid  materials  by  hand.  Both  these 
charging  holes  are  closed  with  neat  fitting  brick  lined  doors,  which  are 
lifted  by  means  of  compressed  air  cylinders  in  much  the  same  way  as  open 
hearth  doors. 


SECTION   VIII. 

OPERATION   OF  THE   FURNACE. 

Practice  at  Duquesne  Plant:  The  Duquesne  furnace  is  used  to  make 
plain  steels  of  any  carbon  content  and  many  different  alloy  steels.  For  all 
the  steels  made  in  the  furnace  the  raw  material  charged  is  finished  basic 
open  hearth  steel,  hence  the  refining  in  the  electric  furnace  consists  of 
deoxidizing  and  desulphurizing  only.  Unless  the  specifications  on  the 
basic  steel  should  coincide  with  those  for  the  electric,  which  is  seldom  the 
case,  additions  are  made  to  the  charge  either  in  the  transfer  ladle  or  in 


280  "ELECTRIC  PROCESS 


the  furnace.  No  additions  of  any  kind  are  made  in  the  pouring  ladle  or  at 
the  time  of  tapping,  as  is  the  common  practice  in  making  open  hearth 
steel.  A  good  example  is  furnished  in  the  case  of  carbon.  When  it  is 
necessary  to  raise  the  per  cent,  of  this  element,  as  is  the  case  on  orders 
calling  for  a  higher  per  cent,  than  that  of  the  open  hearth  heat,  the  amount 
required  above  that  supplied  by  other  additions  is  added,  in  the  form  of 
anthracite  coal,  to  the  steel  in  the  transfer  ladle,  in  the  furnace,  or  a  part 
in  both.  Additions  of  other  elements  are,  as  a  rule,  added  after  deoxida- 
tion  of  the  metal  is  well  advanced  or  completed.  This  ability  to  finish 
the  heat  in  the  furnace  is  a  decided  advantage  in  favor  of  the  electric 
process,  as  a  more  homogeneous  product  is  thus  obtained. 

Charging:  Omitting  the  mechanical  and  electrical  features,  the 
operation  of  the  furnace,  in  general,  is  carried  out  as  follows: — Approxi- 
mately twenty  tons  of  a  suitable  open  hearth  heat  is  teemed  from  the 
steel  ladle  into  the  charging  ladle,  for  the  electric  furnace.  This  charge  is 
then  conveyed  by  a  dinkey,  over  a  narrow  gauge  track,  to  the  furnace, 
into  which  it  is  poured  through  a  portable  spout.  During  the  pouring,  a 
test  for  chemical  analysis  is  taken,  and  upon  the  results  of  this  analysis  is 
based  the  approximate  amount  of  carbon  and  manganese  to  be  added.  An 
increase  of  three  to  five  points  in  the  manganese  content  of  the  steel  usually 
occurs  during  the  deoxidizing  period,  and  must  be  allowed  for.  If  a  medium 
or  high  carbon  heat  is  being  made  from  a  low  carbon  open  hearth  heat,  requiring 
the  addition  of  a  large  amount  of  carbon,  the  greater  portion  of  this 
element  is  added  in  the  form  of  anthracite  coal,  which  is  thrown  into  the 
furnace  as  the  heat  is  being  charged.  This  procedure  is  necessary  to 
insure  that  the  coal  will  be  absorbed  by  the  steel. 

Deoxidizing:  As  soon  as  the  charging  has  been  completed,  the  elec- 
trodes are  adjusted,  and  the  current  is  turned  on.  Since  the  charge  usually 
freezes  over  on  top,  especially  in  the  case  of  low  carbon  steels,  nothing 
further  is  done  until  this  solidified  layer  is  completely  melted.  As  soon 
as  the  bath  is  in  a  state  of  complete  fusion,  the  first  slag  mixture,  consisting 
approximately  of  four  parts  lime  and  one  part  fluorspar  or  one  part  clean 
sand  for  low  carbon  heats,  is  added;  for  high  carbon  heats,  the  mixture 
may  contain  about  one-third  part  coke  dust.  Soon  after  this  addition,  the 
second  sample  for  chemical  analysis  is  taken  to  determine  the  per  cent,  of 
carbon  and  manganese  in  the  bath,  and  while  these  determinations  are 
being  made  further  additions  of  the  first  slag  mixture  takes  place.  Samples 
of  the  slag  taken  at  this  time  are  usually  brown  in  color  and  contain  vary- 
ing amounts  of  manganese  oxide,  which  fact,  shows  that  the  iron  oxide  in  the 
steel  is  being  reduced  by  the  manganese  present.  A  decided  brown  color 
can  be  taken  to  indicate  that  the  deoxidation  of  the  steel  is  well  advanced. 
A  second  slag  mixture  composed  of  suitable  proportions  of  lime,  fluor  spar, 
sand  and  coke  dust  is  now  added.  Soon  after  the  addition  of  this  mixture 
the  slag  becomes  less  vitrious,  shows  a  tendency  to  slake,  and  begins  to 


DUQUESNE  PRACTICE  281 

fade  in  color.  If  the  heating  be  continued  long  enough,  with  proper  addi- 
tions of  the  carbonaceous  flux,  samples  of  the  slag  will  slake  when  cold  and 
become  gray,  or  even  white,  in  color.  Such  behavior  of  the  slag  indicates 
that  the  deoxidation  of  the  bath  of  metal  and  slag  has  been  completed. 
This  condition  is  also  determined  by  means  of  the  water  test.  If  at  this 
time  a  small  sample  of  the  slag  while  hot  be  immersed  in  a  little  water, 
the  odor  of  hydrogen  sulphide  can  usually  be  detected,  and,  if  deoxidation 
is  complete,  the  smell  of  acetylene  gas  can  also  be  detected. 

Finishing  the  Heats:  During  the  deoxidation  of  the  bath  the  results 
of  the  second  chemical  analysis  have  been  reported,  and  if  the  per  cents, 
of  carbon  and  manganese  are  satisfactory,  any  alloys  that  may  be  required 
by  the  order  are  added  as  soon  as  the  slag  condition  will  permit.  If  the 
carbon  content  should  be  too  low,  it  is  raised  to  the  required  point  by  the 
addition  of  a  proper  weight  of  cold,  very  low  phosphorus  pig  iron.  The 
bath  is  chilled  somewhat  by  the  addition  of  the  alloys,  especially  if  they 
are  added  in  large  amounts,  and  about  three-quarters  of  an  hour  is  required 
to  heat  the  bath  up  to  the  tapping  temperature.  Besides,  in  order  to  give 
the  alloys  time  to  mix  with  the  steel,  no  additions  are  made  for  thirty 
minutes  before  tapping  except  in  the  case  of  50%  ferro  silicon,  which  is 
added  ten  to  fifteen  minutes  before  tapping  to  avoid  losses  of  the 
element. 

Tapping  and  Teeming:  When  enough  time  has  elapsed  to  melt  all  the 
alloys  or  other  additions,  slaking  and  water  tests  are  made  on  the  slag,  and 
if  these  indicate  a  satisfactory  condition  of  the  slag,  the  heat  is  tapped.  In 
tapping  the  heats,  care  is  taken  to  prevent  slag  from  running  into  the  steel 
ladle  with  the  metal.  The  special  skimmer  with  which  the  tapping  hole  is 
provided  for  this  purpose  has  already  been  mentioned.  The  steel  is  teemed 
very  carefully,  being  usually  box  poured.  In  this  method  of  teeming  the 
stream  of  molten  metal  from  the  ladle  flows  into  the  middle  of  a  box  made 
in  three  compartments.  From  the  middle  compartment  the  steel  overflows 
into  the  two  end  ones,  which  are  provided  with  nozzles.  This  arrangement 
permits  these  nozzles  to  be  carefully  centered  over  two  ingot  moulds  before 
the  pouring  is  begun.  Special  care  is  taken  in  preparing  the  ingot  moulds, 
so  as  to  prevent  ingot  defects  due  to  bad  moulds.  The  steel  is  allowed 
to  stand  two  hours  in  the  moulds,  so  as  to  insure  that  solidification  is 
complete  before  it  is  stripped. 

Scrap  Heats:  Besides  the  refining  of  molten  open  hearth  steel,  which 
has  just  been  described,  the  furnace  is  occasionally  used  to  make  steel 
from  scrap.  When  using  scrap,  two  methods  may  be  followed.  Thus, 
the  charge  may  consist  of  cold  scrap  or  be  made  up  of  scrap  and  molten 
steel.  When  scrap  alone  is  used,  it  must  be  small,  and  the  coarser  material 
is  charged  first  with  the  finest  on  the  top.  Even  then  the  power  fluctuations 
are  great,  and  some  difficulty  is  experienced  in  melting  the  scrap.  These 


282  ELECTRIC  PROCESS 


difficulties  are  over-come  for  the  most  part  by  starting  the  furnace  on  a 
short  charge  of  molten  steel  and  then  adding  the  scrap  to  this  charge. 
This  latter  method  is  the  one  employed  most  often  at  this  plant.  After 
the  melting  period  the  procedure  is  then  the  same  as  that  already  described 
for  molten  charges.  An  examination  of  the  following  tables  will  give  a  more 
concrete  idea  of  the  method  of  handling  the  different  kinds  of  steel  made 
in  the  electric  furnace. 

Table  38.     Showing  History  of  a  Heat  of  Low  Carbon  Plain  Steel 
Made  in  the  Electric  Furnace. 

Analysis  of  molten  charge — steel  as  finished  at  open  hearth:  C.=.09%; 
Mn.=.38%;  P.=.014%;  S=.043%. 

Order:  C.  .10/.15%;  Mn.=.30/.50%;  P.  under  .035%;  S.  under  .040%; 
Si.  under  .04%. 

Time  Additions 

8:10    Charge,  46700  Ibs.     Test.   C.=.06%;   Mn.=.33%;  P.=.010%; 

S.=.038%. 
8:35    Power  on. 

9:35     1st  slag  mixture.     Lime,  500  Ibs.,  fluor  spar,  150  Ibs. 
9:50    485  Ibs.  pig  iron  added. 
10:00    %  second  slag  mixture,  Lime,  750  Lbs.,  fluor  spar,  125  Ibs.,  coke 

dust,  100  Ibs;  sand,  100  Ibs. 
10:05    Sample  for  chemical  analysis. 
10:20     104  Ibs.  ferro  manganese  added  cold.     (Laboratory  report  shows 

C.=.08%;Mn.=.19%.) 

10:30    Chemical  analysis,  C.=.10%;  Mn.=.32%. 
10:45    50  Ibs.  Ferro  manganese  added  cold. 
10:50    300  Ibs.  pig  iron  added  cold. 
10:55     y%  second  slag  mixture. 
11:00    34  third  slag  mixture — Lime,  100  Ibs.;  fluor  spar,  30  Ibs.;  coke  dust, 

75  Ibs. 

11 :30    34  third  slag  mixture. 
11 :40    34  third  slag  mixture. 
11 :45    34  third  slag  mixture. 
12:00    20  Ibs.  coke  dust. 
12:30    30  Ibs.  coke  dust. 
12:35    50  Ibs.  ferro  manganese  added  cold. 
12:50    Heat  tapped. 

Final  analysis:     C.=.12%;  Mn.=.35%;   P.=.007%;  S.=.035%; 


DUQUESNE  PRACTICE  283 


Table  39.     A  Heat  of  High  Carbon  Plain  Steel. 


Molten  charge— Steel  as  finished  at  open  hearth — C.=.19%;  Mn.=.28%; 
P.=.016%;   S.=.041%; 

Order:   C.=.95/1.Q5%;   Mn.=.20/.35%;   P.=under.030%;    S.=under.030%; 
Si.=.10/.25%. 


Time  Additions 

3:20    150  Ibs.  Anthracite  Coal  added  to  ladle. 

3:30    Charge,  52400  Ibs.     Test:  C.=.29%;   Mn.=.23%;   P.=.012%; 

S.=.042%. 

660  Ibs.  Coal  added  in  furnace  as  heat  is  being  charged. 
3:35    155  Ibs.  coal  added. 
3:40    Power  on. 

5:35     %  first  slag  mixture.     Lime,  1200  Ibs. ;  fluor  spar,  200  Ibs. ;  coke  dust, 
100  Ibs;  sand,  100  Ibs. 

»•'    m.       •     i   A      i      •  /front  door, —C.=.85%;  Mn.=.29%. 
6:15    Chemical  Analysis<   .  ,     ,  0  ' 0>  '° 

\side  door,  — C.=.85%;  Mn.=.28%. 

6:15  %  first  slag  mixture. 

6:30  ^s  first  slag  mixture. 

6:40  %  first  slag  mixture. 

6:50  }4  first  slag  mixture. 

7:00  %  second  slag  mixture.     Lime,  100  Ibs.;  fluor  spar,  25  Ibs.;  coke 

dust,  15  Ibs. 

7:05  1700  Ibs.  pig  iron. 

7:10  Y$  second  slag  mixture. 

7:15  Y^  second  slag  mixture. 

7 :20  175  Ibs.  50%  ferro  silicon. 

7:40  Power  off,  and  heat  tapped. 

Final  analysis,  C.=.97%;  Mn.=.29%;  P.=.007%;  S.=.016%;  Si.=.19%. 


284  ELECTRIC  PROCESS 


Table  40.     A  Low  Carbon  Alloy  Heat. 


Molten  Charge  as  finished  at  Open  Hearth,  C.=.09%;  Mn.=.34%; 
P.=.015%;  S.=.034%. 

Order:     C.=.12/.20%;    Mn.=.40/.70%;    P.=under    .040;%    S.=under 
.040%;  Si.==under  .20%;  Cr.=.40/.80%;  Ni.=1.00/1.75%. 


Time  Additions 

10:55    Charge,  50800  Ibs.     Test,   C.=.08%;   Mn.=.29%;  P.=.010%; 
S.=.042%. 

11:15    Power  on. 

12:00    First  slag  mixture.     Lime,  500  Ibs.;  fluor  spar,  150  Ibs.; 
12:30    %  second  slag  mixture.     Lime,  750  Ibs.;  fluor  spar,  125  Ibs.;  coke 
dust,  100  Ibs;  sand,  100  Ibs. 

.  /front  door,  C.=.08%;  Mn.=.24%. 

12:45     Chemical  Analysis<   .  ,     ,         '  ' °'  'Q 

[side  door,  C.=.08%;  Mn.=.22%. 

12:50  200  Ibs.  ferro  manganese;  Mn.=78%. 

12:55  446  Ibs.  ferro  chrome;  Cr.=70%. 

1:00  730  Ibs.  nickel;  Ni.  =99%. 

1:30  Yz  third  slag  mixture — Lime,  50  Ibs.;  coke  dust,  75  Ibs. 

1 :45  3^  third  slag  mixture. 

1:50  30  ^3S.  ferro  manganese  and  60  Ibs.  50%  ferro  silicon. 

2:00  Heat  tapped. 

Final  Analysis,  C.=.20%;    Mn.=.51%;    P.=.009%;    S.=.028%; 
Si.=.03%;  Cr.=.54%;  Ni.=1.28%. 


DUQUESNE  PRACTICE  285 


Table  41.     A  High  Carbon  Alloy  Heat. 

Molten  charge — Steel  as  finished   at  open  hearth — C.=.20%; 
Mn.=.35%;  P.=.010%;  S.=.035%. 

Order:    C.=.95/1.05%;    Mn.=.35/.50%;    P.=under  .030%;    S.=under 
.030%;  Si.=under  .03%;  Cr.=1.35/1.65%;  V.==over  .18%. 


Time  Additions 

11:48     150  Ibs.  anthracite  coal  added  in  transfer  ladle. 

11:50    Charge,  54500  Ibs.     Test,  C.=.07%;  Mn.=.34%;    P.=.006%; 

S.=.040%. 
12:05    Power  on. 

12:50    %  first  slag  mixture— Lime,  1300  Ibs. ;  fluor  spar,  160  Ibs;  sand,  125  Ibs. 
'Front  door,  C.=.89%;  Mn.=.34%. 


1:20    Chemical  anal ysiss ,-,.,     ,         ^       nn~    -,         0_~ 
(Side  door,  C.=.90%;  Mn.=.35%. 

1:25    %  slag  mixture. 

1:35    y&  second  slag  mixture.     Lime,  150  Ibs.;  coke  dust,  150  Ibs. 

2:00     1180  Ibs.  ferro  chrome,  Cr.=70%. 

2:10  to  2:40    Remainder  of  second  slag  mixture  added  at  intervals  of  ten 

minutes. 

2:55    353  Ibs.  ferro  vanadium.  V.=35% 
3:05    60  Ibs.,  50%  ferro  silicon. 
3:30    Heat  tapped. 

Final  analysis,  C.=.99%;  Mn.=.35%;  P.=.006%;  S.=.017%;  Si.=.07%; 
Cr.=1.44%;V.=.22%. 


286  ELECTRIC  PROCESS 


SECTION   IX. 

THE   CHEMISTRY  OP  THE   PROCESS. 

Deoxidation  of  the  Bath:  The  tracing  of  the  chemical  changes  that 
take  place  in  the  process  employed  at  this  plant  furnishes  an  interesting 
study.  Since  the  charge  is  finished  open  hearth  steel  containing  the  usual 
amount  of  manganese,  it  is  to  be  expected  that  this  element  would  play 
a  most  important  part  in  the  deoxidation  of  the  steel.  The  fact,  plainly 
shown  by  the  preceding  records,  that  the  manganese  is  usually  several 
points  lower  in  the  charging  test  than  in  the  open  hearth  steel  is  proof  of 
its  deoxidizing  action,  which  would  be  expected  to  continue  in  the  furnace. 
The  removal  of  oxygen,  then,  is  represented  by  the  following  reaction: 
FeO+Mn=MnO+Fe.  The  MnO,  being  less  soluble  in  the  molten  metal 
than  FeO,  rises  to  the  surface  and  becomes  a  part  of  the  slag.  This  action 
is  identical  with  that  in  the  ladle  in  finishing  open  hearth  steel,  but  the 
result  is  not  the  same  in  the  two  processes  for  two  reasons:  First,  for  want 
of  time,  the  deoxidation  is  not  completed  in  the  ladle,  whereas  in  the  electric 
furnace  it  is  complete.  Second,  the  MnO  in  the  electric  furnace  comes 
under  the  reducing  action  of  the  carbon  contained  in  the  slag  mixture  and 
is  reduced,  thus:  MnO+C=Mn+CO.  The  carbon  monoxide,  CO.  being  a 
gas,  becomes  a  part  of  the  atmosphere  of  the  furnace,  and  the  manganese 
returns  to  the  bath,  as  is  indicated  by  the  fact  that  the  per  cent,  manganese 
in  the  steel  usually  rises  after  the  addition  of  the  carbonaceous  flux. 

Desulphurizing  the  Metal:  With  the  elimination  of  oxides  from  the 
slag,  the  lime,  under  the  influence  of  the  extremely  high  temperature  of 
the  arc  which  prevails  under  and  in  the  immediate  vicinity  of  the  electrodes, 
begins  to  be  reduced  by  the  carbon  of  the  coke  dust,  with  the  consequent 
formation  of  calcium  carbide,  thus:  CaO+3C=CaC2+CO.  It  is  at  this 
point  that  desulphurization  takes  place.  Since  manganese  sulphide,  like 
the  oxide,  is  less  soluble  in  iron  than  ferrous  sulphide,  it  is  probable  that 
this  element  also  aids  in  this  process.  Whether  manganese  sulphide  or 
ferrous  sulphide  plays  the  most  important  role  in  the  sulphur  reactions  is 
difficult  to  decide,  but  that  the  removal  of  the  sulphur  from  the  bath  takes 
place  through  the  formation  of  calcium  sulphide,  which  is  insoluble  in  molten 
iron,  cannot  be  doubted.  These  reactions  are  two  in  number  and  may  be 
written  thus: 

/FeS    ,  /Fe 


\MnS-1—-'-0-  Mn+CaS+C° 


CHEMISTRY 


287 


With  metallic  oxides  present  in  the  slag,  neither  of  these  reactions  will  take 
place,  ae  the  oxide  would  react  with  the  calcium  sulphide,  thus: 


CaS+ 


/FeO      /FeS 


"\MnO~~\MnS" 
and  with  calcium  carbide  according  to  this  reaction: 


Hence  the  presence  of  CaC2  in  the  slag  is  a  guarantee  that  the  bath  is 
deoxidized.  In  the  water  test  the  presence  of  considerable  quantities  of 
CaC2  in  the  slag  is  detected  by  the  odor  of  acetylene  gas,  which  is  generated 
in  accordance  with  the  following  reactions:  CaC2+H2O=C2H2+CaO. 
These  facts  are  further  illustrated  by  the  following  analysis  of  heats  and 
slags:  Slags  AZ  No.  3  and  AZ  No.  5  illustrate  an  undesirable  and  a  desirable 
slag,  respectively.  The  relatively  high  iron  and  manganese  content  of  AZ 
No.  3  indicate  incomplete  deoxidation,  with  a  low  sulphur  and  calcium 
carbide  content  resulting. 

Table  42.     Analysis  of  Tests  from  Electric  Furnace  Heats. 


Heat  Number 

Testa 

Carbon 

% 

Mang. 

% 

Phos. 

% 

Sul. 

% 

Si. 

% 

Primary  

.16 

.35 

.010 

.036 

AZ  No.  1,   (O.  H.  Heat    83023) 

1st  Preliminary 

.80 

.35 

.006 

.023 

2d 

.80 

Final  

.82 

.35 

.010 

.020 

.16 

Primary  

.20 

.44 

.012 

.042 

AZ  No.  2,   (O.  H.  Heat    88026) 

Preliminary.  .  . 

.61 

.43 

.010 

.025 

Final  

.67 

.60 

.009 

.024 

•• 

Charging  

.18 

.41 

.005 

.024 

.. 

No.  1  Electrode 

.20 

.60 

.004 

.020 

.  . 

AZ  No.  3,    (0.  H.  Heat    84598) 

No.  2 

.19 

.60 

.006 

.020 

No.  3 

.21 

.59 

.005 

.020 

Final  

.22 

.58 

.004 

.021 

Charging  

.19 

.34 

.010 

.032 

.<; 

No.  1  Electrode 

.22 

.53 

.007 

.026 

.  . 

AZ  No.  4,    (O.  H.  Heat  101523) 

No.  2 

.22 

.54 

.009 

.023 

No.  3 

.22 

.54 

.009 

.023 

Final  

.20 

.47 

.006 

.029 

•• 

Charging  

.28 

.36 

.009 

.040 

AZ  No.  5,   (O.  H.  Heat  101524) 

No.  1  Electrode 

.34 

.54 

.007 

.017 

No.  2 

.32 

.55 

.006 

.015 

Final  

.33 

.52 

.007 

.020 

288  ELECTRIC  PROCESS 


Table  43.     Partial  Analysis  of  Final  Electric  Furnace  Slags. 


Heat  No.'s 

Silica  

AZ  No.  3 

.  .     19.58% 

AZ  No.  4 

20.48% 

AZ  No.  5 

18.40% 

Iron              

1.09 

.72 

.32 

Total  Lime  
Magnesia  
]Vlanganese 

.  .     60.38 
.  .     10.32 
.62 

61.82 
8.40 
.60 

61.26 
7.27 
.35 

Sulphur  

.85 

.80 

1.30 

Calcium  carbide  .  . 
Alumina  .  . 

.32 
3.04 

.19 
3.61 

.46 
5.95 

Difficult  Specifications:  While  the  electric  furnace  affords  means  of 
making  steel  to  very  difficult  specifications  and  with  a  greater  degree  of 
accuracy  than  is  possible  in  other  processes,  yet  it  has  its  limitations. 
The  case  of  sulphur  furnishes  an  example.  From  what  has  just  been  said, 
the  importance  of  carbon  in  the'  elimination  of  both  oxygen  and  sulphur  is 
evident.  In  low  carbon  steels  the  lowering  of  the  sulphur  content  to  any 
considerable  degree  becomes  a  difficult  problem,  because,  if  the  flux  be  made 
highly  carbonaceous,  a  necessary  condition,  there  is  danger  that  the  steel 
will  absorb  carbon  from  the  slag,  and  thus  raise  the  carbon  content  of  the 
steel  above  the  requirements.  In  the  high  carbon  stee.s,  the  absorption  of 
carbon  by  the  steel  can  be  allowed  for  and  presents  no  difficulty,  so  a  more 
highly  carbonaceous  flux  may  be  used  than  with  low  carbons,  and  a  greater 
removal  of  sulphur  results.  As  previously  indicated,  the  elimination  of 
sulphur  may  be  brought  about  by  the  use  of  silicon,  as  shown  in  the  following 
reactions  : 


But  while  it  is  claimed  that  little  more  than  the  theoretical  amount  of 
silicon  is  required,  in  actual  practice  a  residue  of  silicon  in  the  steel  is 
unavoidable.  Hence,  this  method  could  not  be  employed  to  produce  silicon 
free  steel.  Similar  to  the  method  of  desulphurizing  with  carbon,  these 
reactions  will  take  place  only  after  the  bath  has  been  completely  deoxidized. 
For  low  carbon  steels,  then,  the  limit  for  sulphur  should  be  .040%,  while  for 
high  carbons  this  limit  could  be  reduced  to  .030%.  To  guarantee  lower 
limits  than  these  would  mean  increased  cost  in  production  out  of  proportion 
to  the  benefits  to  be  derived,  except  in  the  case  of  steal  that  is  to  be  used 
for  certain  special  purposes.  Since  the  phosphorus  is  removed  in  the  basic 
open  hearth,  the  same  range  in  per  cent,  of  this  element  as  is  customary 
to  allow  in  open  hearth  steel  should  be  allowed  in  electric  steel.  As  to 
alloying  elements,  the  variation  in  the  composition  of  the  alloys  used 
makes  it  desirable  to  secure  as  wide  a  range  as  possible  in  the  specifications 
for  such  elements. 


PROPERTIES  OF  ELECTRIC  STEEL          289 


SECTION   X. 

PROPERTIES   AND   USES   OF  ELECTRIC   STEEL. 

Properties  of  Electric  Steel:  We  can  deal  with  this  topic  in  a  no 
more  fitting  way  than  to  quote  from  impartial  investigators.  The  following 
is  taken  from  a  paper  by  Messrs.  Lyon  and  Keeney  of  the  Bureau  of  Mines: 
"For  many  years  all  high  grade  steels  were  manufactured  by  the  crucible 
process,  but  since  the  advent  of  the  electric  furnace  there  has  been  a  gradual 
adoption  of  that  furnace  for  refining  steel.  For  the  complete  refining  of 
the  highest  grades  of  steel  the  use  of  the  electric  furnace  is  now  thoroughly 
established.  Any  products  that  can  be  made  by  the  crucible  process  can 
be  made  by  the  electric  furnace,  and  in  most  cases  with  cheaper  raw 
materials  and  at  a  low  cost.  In  the  electric  furnace  complex  alloy  steels 
can  be  made  with  precision.  The  high  temperatures  attainable  facilitate 
the  reactions,  and  alloys  need  not  be  used  so  largely  for  the  purpose  of 
removing  gas.  Very  low  carbon  steels  can  be  kept  fluid  at  the  high  tem- 
peratures. Steels  free  from  impurities  and  of  great  value  for  electrical 
apparatus  can  be  made.  With  the  electric  furnace  large  castings  can  be 
made  from  one  furnace,  whereas  in  the  crucible  process  steel  from  several 
crucibles  must  be  used.  For  small  castings,  which  require  a  very  high 
grade  metal  free  from  slags  and  oxides,  electrically  refined  steel  is  especially 
adapted.  The  electric  furnace  gives  a  metal  of  low  or  high  carbon  content 
as  desired,  hot  enough  to  pour  into  thin  molds,  and  steel  free  from  slags 
and  gases." 

"There  is  now  a  tendency  among  customers  of  rail  and  structural  steel 
to  require  a  higher  grade  steel  at  an  increased  price  rather  than  steel  of 
acid  Bessemer  or  even  of  basic  open  hearth  grade  at  a  lower  price.  With 
the  high  cost  of  power  that  now  prevails  throughout  the  steel  centers  of 
the  United  States  the  electric  furnace  cannot  compete  profitably  with  either 
the  acid  Bessemer  or  the  basic  open  hearth  process  in  manufacturing  steel  of 
like  grade  from  pig  iron.  It  is  in  combination  with  either  of  these  processes 
that  the  electric  furnace  seems  destined  to  be  prominent  in  steel  manu- 
facture." 

"Experiments  conducted  by  the  United  States  Steel  Corporation  during 
the  past  four  years  show  that,  as  compared  with  the  acid  Bessemer  and 
basic  open  hearth  processes,  the  electric  process  has  the  following  advan- 
tages: A  more  complete  removal  of  oxygen;  the  absence  of  oxides  caused 
by  the  addition  of  silicon,  manganese,  etc; — the  production  of  steel  ingots 
of  8  tons  weight  and  smaller  that  are  practically  free  from  segregation; 
reduction  of  the  sulphur  content  to  0.005  per  cent.,  if  desired;  reduction 
of  the  phosphorus  content  to  .005  per  cent,  as  in  the  basic  open  hearth 
process,  but  with  complete  removal  of  oxygen.'* 


290 


ELECTRIC  PROCESS 


"About  5,600  tons  of  standard  electric  rails  from  electric  furnace  steel 
have  been  in  service  in  the  United  States  for  the  past  two  years  (prior  to 
1914).  These  rails  have  been  subjected  to  all  sorts  of  weather  and  to 
temperatures  as  low  as — 52°  F.  It  seems  that  rails  made  by  the  basic 
electric  process  can  be  made  softer  than  by  either  the  acid  Bessemer  or 
basic  open  hearth  processes  and  yet  show  highly  satisfactory  wearing 
qualities." 

"No  steel  rails  made  by  the  basic  electric  process  in  service  in  this 
country  have  been  broken.  Electric  furnace  steel  of  a  given  tensile  strength 
has  a  slightly  greater  elongation  than  basic  open  hearth  steel  and  is  some- 
what denser  than  basic  open  hearth  or  acid  Bessemer  steel.'! 

The  results  of  some  comparative  tests,  made  at  South  Chicago  of 
electric  furnace  steel  for  plates  and  basic  open  hearth  steel  for  plates  were 
as  follows: — 


Table  44.     Comparison  of  Mechanical  Properties  of  Electric  and 
Open  Hearth  Plate  Steel. 


ELECTRIC 


OPEN  HEARTH 


Carbon 
Content 
Per  Cent. 

Ultimate 
Strength 
per  Sq.  In. 
Pounds 

Elongation 
on  2  Inches 
Per  Cent. 

Carbon 
Content 
Per  Cent. 

Ultimate 
Strength 
per  Sq.  In. 
Pounds 

Elongation 
on  2  Inches 
Per  Cent. 

0.08 

59,194 

27.25 

0.08 

51,690 

32.00 

.12 

64,080 

26.05 

.12 

56,510 

29.70 

.16 

69,220 

25.25 

.16 

52,901 

28.61 

.20 

72,853 

22.82 

.20 

58,294 

28.82 

.24 

69,540 

23.12 

.24 

63,560 

26.25 

The  results  show  a  15.5  per  cent,  increase  in  ultimate  strength  and 
11.3%  decrease  in  elongation  for  electric  steel,  as  compared  with  open  hearth 
plate  steel  of  approximately  the  same  chemical  composition." 

Illinois  Steel  Company's  Tests  on  Rails :  The  Illinois  Steel  Company 
have  conducted  a  series  of  experiments  from  which  it  was  shown  that  electric 
steel  is  considerably  more  ductile  at  low  temperatures  than  either  the  open 
hearth  or  the  Bessemer  steel.  In  these  tests  about  900  pieces  of  electric, 
open  hearth,  and  Bessemer  rails  were  tested  at  temperatures  ranging  from 
70°  F.  to  —50°  F.,  and  the  results  indicated  that  while  all  these  steels 
showed  a  marked  decrease  in  resistance  to  shock  as  the  temperature  was 
lowered,  the  electric  steel  was  relatively  more  ductile  than  either  of  the 
other  two.  The  following  table  is  a  summary  of  the  results  obtained  with 


USES  OF  ELECTRIC  STEEL 


291 


two  open  hearth  and  two  electric  heats  of  similar  composition  chemically, 
as  shown  by  analysis,  and  may  be  taken  as  typical  of  the  general  results 
obtained. 

Table  45.     Comparison  of  Tests  on  Open  Hearth  and  Electric  Steel 
Railroad  Rails  at  Different  Temperatures. 

Number  of  Tests,  242. 


Temp 
Deg'sF. 

AVE.  No.  BLOWS  TO 
BREAK  RAILS 

DEFLECTION  BEFORE 
BREAKING 

ELONGATION  IN  12  IN. 

Elec. 

O.H. 

Comparison 

Elec. 

O.H. 

Comparison 

Elec. 

O.H. 

Comparison 

O.H. 

Over 

E. 

E.  Over 
0.  H. 

Inches 

Inches 

O.H. 

OverE. 

E.  Over 
O.H. 

Inches 

Inches 

O.H. 

Over  E. 

E.Over 
0.  H. 

-j-60 

3.48 

3.64 

5% 

2.96 

3.36 

14% 

.808 

.929 

15% 



0 

4.41 

3.82 

15% 

1.41 

1.23 

15% 

.404 

.397 

2% 

—30 

4.55 

2.24 

103% 

1.46 

.58 

152% 

.420 

.201 

109% 

—  40 

3.31 

2.03 

65% 

.91 

.43 

112% 

.297 

.141 

111% 

Uses  of  Electric  Steel:  As  to  the  uses  of  electric  steel,  little  need  be 
said  except  it  may  be  used  with  confidence  wherever  a  steel  of  higher 
quality  than  that  furnished  by  the  open  hearth  process  is  desirable. 
So  far,  the  demand  for  this  steel  has  been  in  advance  of  the  supply,  and 
its  application  is  becoming  more  and  more  general.  Among  those  with 
whom  it  has  found  favor  and  by  whom  it  is  now  being  used,  are  manu- 
facturers of  automobiles,  motorcycles,  motor  accessories,  areoplanes, 
machinery,  engines,  agricultural  implements,  tools,  guns  and  munitions, 
and  by  the  railroads.  The  fact  that  it  is  being  used  more  and  more  in 
place  of  crucible  steel  is  evidence  of  its  superior  quality. 

Summary:  In  order  to  cover  the  whole  subject  of  electric  steel 
making  satisfactorily  in  so  brief  a  manner,  it  has  been  necessary  to  treat 
the  subject  from  several  different  view  points,  which  method  is  likely  to 
be  confusing,  with  the  result  that  the  reader  may  have  lost  sight  of  some 
important  points.  In  order  that  these  points  may  receive  proper  emphasis, 
the  following  summary  of  the  chapter  is  appended: 

1.  Of  the  many  furnaces  in  use  no  one  can  be  said  to  possess  any  great 
advantage  over  any  other  from  a  metallurgical  point  of  view,  with  the 
exception  that  higher  temperatures  may  be  obtained  with  furnaces  of  the 
arc  type  than  with  the  induction  type. 

2.  The  only  effect  of  the  electric  current  is  in  the  production  of  heat. 


292  SUMMARY 


3.  The  electric  process  is  the  only  one  in  which  impurities  are  not 
added  to  the  steel  by  the  operation. 

4.  The   electro-thermal  process  affords  the  only  positive  means  of 
desulphurizing   and   deoxidizing   steel   simultaneously  and    in    the    same 
operation. 

5.  It  permits  the  addition  of  all  alloying  elements  while  the  steel  is 
in  the  furnace. 

6.  It  provides  a  way  for  remelting  alloy  steel  scrap  and  producing  a 
product  of  high  quality  without  loss. 

7.  Steel  produced  by  this  process  exhibits  some  unusual   wearing 
qualities. 

8.  In  quality,  steel  made  by  this  process  equals  that  of  the  best  grades 
of  crucible  steel. 

9.  Much  larger  quantities  of  metal  may  be  treated  in  one  operation 
than  is  possible  by  the  crucible  process. 

10.  It  gives  a  product  that  is  uniform  in  quality  for  any  given  heat. 

11.  Steels  refined  in  the  electric  furnace  are  freest  from  segregation. 

12.  Steels  made  in  the  electric  furnace  are  free  from  slag  and  other 
inclusions. 

13.  Electric  steel  is  comparatively  more  ductile  at  low  temperatures 
than  Bessemer  or  open  hearth. 

14.  Considering  the  various  methods  from  an  economical  point  of 
view,  the  duplexing  process  in  which  the  electric  furnace  is  used  in  con- 
junction with  the  basic  open  hearth  combines  the  greatest  capacity  and 
efficiency  with  highest  quality  of  product. 


DUPLEX  PROCESS  293 


CHAPTER  X. 

THE  DUPLEX  AND  TRIPLEX  PROCESSES. 

SECTION   I. 

GENEBAL  FEATURES   OF   THE    DUPLEX   PROCESS. 

What  the  Duplex  Process  Is :  The  term  duplex  process  may  be  applied 
to  a  combination  of  any  two  processes  for  manufacturing  steel,  but  it  is 
customary  among  the  steel  men  of  this  country,  at  least,  to  restrict  the 
term  to  mean  only  a  combination  of  the  acid  Bessemer  and  the  basic  open 
hearth  process,  in  which  the  latter  plays  the  part  of  a  finishing  process. 
Briefly  described,  the  method,  as  usually  carried  out,  consists,  first,  of 
blowing  molten  basic  iron  in  the  converter  until  the  silicon,  manganese  and 
a  part  of  the  carbon  have  been  oxidized  and  then  transferring  this  semi- 
finished metal  to  a  basic  open  hearth  furnace,  where,  through  the  agencies 
of  iron  oxide  and  lime,  the  phosphorus  and  the  remainder  of  the  carbon 
to  be  removed  are  oxidized.  The  steel  is  then  finished,  recarburized  and 
deoxidized,  according  to  the  usual  open  hearth  practice.  This  combination 
of  processes  may  be  made  in  other  ways,  also.  One  plant,  for  example, 
in  order  to  produce  a  very  low  phosphorus  Bessemer  steel  for  a  certain 
order,  first  oxidized  the  silicon,  manganese,  and  phosphorus  in  the  open 
hearth,  and  then,  by  mixing  this  very  high  carbon  steel  with  Bessemer 
iron  in  suitable  proportions,  succeeded  in  blowing  out  the  carbon  in  the 
converter,  thus  reversing  the  customary  procedure.  But  as  stated  in  the 
beginning,  the  duplex  process  refers  to  the  combination  in  which  the  finishing 
operation  is  conducted  in  and  from  a  basic  open  hearth  furnace. 

Advantages  and  Disadvantages  of  the  Process:  In  the  northern 
district  of  the  United  States  the  chief  advantages  of  the  process,  when 
there  is  a  pressing  demand  for  steel,  is  that  of  the  increased  tonnage  which 
it  produces  in  a  given  time.  Thus,  while  the  product  is  similar  in  quality 
and  of  the  same  grades  as  basic  steel,  the  time  of  the  open  hearth  operation 
is  shortened  by  about  half;  for,  whereas  one  open  hearth  furnace  will  turn 
out  an  average  of  about  fifteen  heats  in  a  week  of  straight  running  by  the 
ordinary  way,  the  same  furnace  operated  as  a  duplexing  unit  will  produce 
about  forty  heats  in  the  same  period.  This  shortening  of  the  time  of  a 
heat  saves  fuel  and  tends  to  prolong  the  life  of  the  furnace,  as  does,  also,  the 
elimination  of  the  silicon  in  the  converter.  The  process  does  not  require 
the  use  of  scrap,  which  fact  may  also  be  an  advantage  to  some  makers. 
Offsetting  these  advantages,  however,  are  the  double  conversion  cost  and 
the  decrease  in  yield,  due  to  the  increased  oxidation,  both  of  which  may  be 
very  serious  drawbacks  to  the  economical  production  of  steej.  In  dull 


294  DUPLEX  PROCESS 


times,  especially,  the  extra  costs  of  maintaining  two  separate  units  may 
more  than  counter-  balance  the  gain  from  the  increased  output. 

Methods  of  Duplexing:  While  the  details  of  the  process  vary  widely 
in  the  different  plants,  there  are  two  general  methods  of  carrying  out  the 
duplexing  process:  Thus,  the  purification  in  the  converter  may  be  carried 
cut  to  the  point  where  the  metal  is  fully  blown  and  represents  a  high  phos- 
phorus steel  which  may  then  be  mixed  with  pig  iron  in  the  open  hearth, 
thus  taking  the  place  of  steel  scrap.  In  this  method  either  a  stationary 
or  a  tilting  furnace  can  be  utilized.  But  the  more  common  method  is  the 
&UQ,  already  mentioned,  in  which  the  carbon  is  only  partially  eliminated 
In  the  converter,  and  the  purification  then  completed  by  the  continuous 
process,  which  is  most  conveniently  carried  out  in  a  Talbot  tilting  furnace. 
A  brief  description  of  these  furnaces  will  simplify  the  description  of  the 
process  to  be  given  shortly. 

The  Talbot  Furnace:  The  object  aimed  at  in  the  design  of  these 
furnaces  is  to  permit  the  removal  of  any  quantity  of  slag  or  metal  or  the 
addition  of  molten  metal,  oxidizing  agents  and  flux  at  any  time  during  the 
working  of  the  charge.  They  are,  therefore,  necessarily  of  the  tilting  type, 
and  are  built  upon  racers  and  rollers  which  rest  upon  the  foundation  in  a 
manner  similar,  in  a  general  way,  to  that  of  the  large  mixers  of  recent  con- 
struction. They  are  rectangular  in  shape,  and  of  about  the  same  proportions 
as  an  ordinary  open  hearth  furnace  as  to  length  and  width,but  they  have  a  much 
greater  depth,  which  increases  their  capacity  for  containing  molten  metal. 
The  frame  work  must  be  of  much  stronger  construction  than  that  for  the 
ordinary  open  hearth  in  order  to  avoid  twisting  stresses  and  vibrations 
which  would  be  very  harmful  to  the  brick  work.  Only  that  section  of  the 
furnace  comprising  the  hearth,  side-walls  and  roof  is  made  tilting;  all  the 
ports  and  flues  are  stationary,  and,  together  with  the  checker  work,  of  the 
same  construction  as  for  the  stationary  furnaces.  In  the  best  types  of  con- 
struction, these  furnaces  are  so  placed  and  the  racers  and  rollers  so  formed  that 
the  center  of  rotation  of  the  furnace  coincides  with  the  center  line  of  the  ports, 
so  that  all  its  parts  always  remain  in  the  same  relation  no  matter  in  what 
direction  or  to  what  degree  the  movable  portion  of  the  furnace  may  be 
tilted.  By  means  of  water  cooled  metal  joints,  the  clearance  between  the 
movable  and  stationary  parts  of  the  ports  is  kept  very  small,  so  that  the 
heating  of  the  furnace  may  continue  even  during  the  tapping  of  a  heat. 
On  the  pouring  side,  these  furnaces  usually  have  but  one  opening,  a  tapping 
hole  located  above  the  slag  line  and  provided  with  a  lip  or  spout  for  directing 
the  stream  of  molten  metal  into  the  steel  ladle.  As  in  the  case  of  the 
stationary  furnace,  doors  for  introducing  the  materials  into  the  furnace 
are  located  in  the  front  side.  But  unlike  the  stationary  types,  the  slag 
notches  are  also  placed  in  front,  usually  one  on  each  side  of  the  middle 
door,  and,  of  course,  at  a  lower  level.  Since  Talbot's  method  is  but  a 
modification  of  the  basic  open  hearth  process,  the  furnaces  are,  as  a  matter 
of  course,  provided  with  basic  linings. 


METHOD  OF  OPERATION  295 


SECTION   II. 

OPERATION   OF  THE   PROCESS. 

An  Example  of  the  Duplexing  Process:  Perhaps  the  best  way  to 
describe  the  duplexing  process  is  through  an  example.  For  this  purpose 
the  method  employed  by  a  large  steel  manufacturing  company  in  the  North, 
whose  plant  represents  one  of  the  most  recent  installations,  is  selected. 
Their  duplexing  plant  consists  of  three  20-ton  converters  and  three  Talbot 
tilting  furnaces,  each  of  which  has  a  capacity  of  approximately  200  tons. 
While  the  practice  may  be  varied  somewhat  to  suit  conditions,  the  process 
at  this  plant  is  usually  carried  out  about  as  follows: 

Preparing  the  Furnace  for  Charging:  The  process  may  be  said  to 
be  continuous  for  a  week,  for  each  week-end  the  tilting  furnace  is  thoroughly 
drained,  the  bottom  and  slag  lines  are  made  up,  the  ports  are  cleaned  and 
repaired,  and  everything  is  made  ready  for  the  week's  campaign.  Of  course, 
during  the  interval  of  this  campaign  the  front  and  back  wall  must  be 
attended  to  and  such  minor  repairs  made  as  are  found  necessary  and  there 
is  time  for.  About  6  p.  m.  Sunday,  after  the  flues  have  been  burned  out 
and  the  gas  is  once  more  on  the  furnace,  the  work  of  preparing  the  slag  is 
begun.  Four  boxes  of  calcined  limestone  and  three  of  roll  scale  are  charged 
and  melted  down.  These  amounts  are  then  repeated,  and  when  again  molten 
the  same  amounts  are  again  charged,  the  total  being  twelve  boxes  of  lime  and 
eight  to  nine  boxes  of  roll  scale.  The  average  weight  of  a  box  of  the 
lime  is  2000  Ibs.  and  of  a  box  of  roll  scale  3000  Ibs.  Considerable  care 
is  given  by  the  melter  to  the  preparation  of  a  good  slag,  for,  as  in  all  open 
hearth  work,  the  success  of  the  process  depends  on  the  slag. 

Charging  Molten  Metal  from  the  Converters  for  the  First  Heat: 

At  midnight,  or  shortly  afterwards,  the  metal  is  ordered  from  the  Bessemer 
department.  An  average  analysis  of  the  mixer  metal  is  as  follows: 

Total  Carbon 3.85  per  cent. 

Silicon 1.55         " 

Manganese 67         " 

Sulphur 040       " 

Phosphorus 365       " 

The  weight  of  this  metal  taken  for  a  Bessemer  heat  is  about  40,000  Ibs.,  less 
the  weight  of  the  scrap  in  the  converter.  Two  Bessemer  heats,  blown  in 
different  vessels,  are  poured  into  a  transfer  ladle  and  taken  to  the  tilting 
furnace.  When  starting  up,  the  first  ladle  contains  metal  blown  down  to 
contain  0.60  per  cent,  carbon,  which  is  allowed  to  remain  to  give  a  little 
action,  or  boil,  in  the  furnace.  This  first  ladle  is  poured  into  the  open  hearth 
furnace  about  midnight.  It  is  followed  by  a  ladle  of  "soft"  metal, 
that  is,  metal  blown  down  to  0.05%  or  0.07%  carbon,  and  then  by  a 


296  DUPLEX  PROCESS 


"kicker,"  or  a  ladle  of  high  carbon  steel.  This  metal  is  blown  down  to 
from  1.5%  to  2.0%  carbon,  and  when  charged  into  the  open  hearth  produces 
a  vigorous  reaction,  or  boil.  The  metal  and  slag  are  thoroughly  mixed 
together  by  this  boil,  and  during  this  reaction  the  phosphorus  is  largely 
removed  from  the  metal  bath  and  passes  into  the  slag.  When  the  action 
has  subsided,  another  "soft"  ladle  and  a  "kicker"  are  charged.  Then, 
if  the  bath  is  found  to  be  low  in  carbon,  another  kicker  ladle  is  added  to  it, 
but  if  high  in  carbon  another  "soft"  ladle  is  charged.  In  this  way  a  bath 
of  metal  of  about  200  tons  is  produced.  The  charge  is  then  worked  down 
like  an  ordinaty  basic  open  hearth  heat  until  ready  for  tapping,  which  is 
usually  at  about  3:30  a.  m. 


Tapping  and  Recarburizing  the  First  Heat :  When  the  bath  is  ready 
for  tapping,  the  tap  hole  is  opened  and  plugged  with  wet  sacking.  The 
furnace  is  then  tilted  for  pouring.  Before  the  sacking  is  burnt  through, 
the  slag  is  up  along  the  back  wall  so  that  clean  metal  free  from  slag  comes 
from  the  furnace.  Only  enough  slag  is  drawn  off  at  the  end  to  cover  the 
steel  in  the  ladle  properly.  Some  of  the  steel  made  in  the  Talbot  furnaces 
is  super  refined  by  the  electric  process,  but  by  far  the  greater  portion  is  made 
into  the  ordinary  commercial  grades  which  is  recarbonized  and  deoxidized 
in  the  ladle  as  for  similar  grades  made  in  stationary  furnaces. 


Preparing  the  Furnace  for  the  Second  Heat:  After  the  first  heat 
is  tapped,  there  is  a  bath  of  about  100  tons  of  metal  with  a  carbon  content 
of  about  .15%  still  in  the  furnace,  covered  with  the  tapping  slag.  Two 
boxes  of  lime  and  two  boxes  of  scale  are  charged,  and  two  boxes  of  burnt 
dolomite  are  used  along  the  slag  line,  around  the  doors,  etc.,  as  found 
necessary.  Then  two  "soft"  ladles  of  blown  metal  are  charged,  and  two 
more  boxes  of  lime,  which  is  followed  by  a  "kicker."  During  the  reaction, 
the  furnace  is  tilted  slightly  forward  and  slag  is  allowed  to  flow  from  the 
front  of  the  furnace  through  the  slag  spouts,  which  are  under  the  doors 
directly  on  each  side  of  the  center  door.  The  slag  falls  into  slag  cars  stand- 
ing on  the  tracks  below.  Practically  all  the  slag  taken  from  the  furnace 
is  removed  in  this  way,  for,  as  mentioned  before,  when  tapping  a  heat  only 
enough  is  taken  to  cover  the  metal  in  the  ladle  properly.  When  the  reaction 
is  over,  another  box  of  lime  is  generally  charged,  and  the  bath  is  worked 
down  in  the  usual  way.  Very  often,  another  box  of  lime  is  spread  over 
the  slag  shortly  before  tapping,  so  that  five  to  six  boxes  of  lime  are  used 
per  heat,  but  as  a  rule  only  two  boxes  of  scale  are  used  he*re.  After  the  heat 
is  tapped,  this  procedure  is  repeated,  enough  slag  being  taken  from  the 
front  of  the  furnace  at  the  time  of  the  reaction  to  maintain  a  constant  and 
proper  volume  of  slag  in  the  furnace.  The  average  time  for  tapping  one 
heat  to  tapping  the  next  is  about  three  hours. 


TRIPLEX  PROCESS  297 


Closing  Down  the  Furnace  for  the  Week  End:  About  midnight  on 
Saturday  the  furnace  is  drained.  The  bath  is  worked  down,  so  that  after 
the  heat  is  tapped  there  are  not  more  than  forty  to  sixty  tons  in  the 
furnace.  Then  this  residue  of  metal  is  tapped  and  made  into  soft  steel, 
for  which  there  is  a  constant  demand,  by  making  the  proper  additions  of 
ferro-manganese  and  recarburizer. 

The  Slag:  At  the  high  temperature  at  which  its  removal  is  effected, 
phosphorus  is  easily  reduced,  so  in  order  to  oxidize,  flux  and  hold  the  phos- 
phorus in  the  open  hearth  slag,  it  is  necessary  that  the  latter  be  very  basic 
and  highly  oxidizing,  as  an  analysis  shows.  The  average  composition  of 
the  slag  is  about  as  follows:  Silica,  SiO2,  6.35%;  ferrous  oxide,  FeO,  21.65%; 
ferric  oxide,  Fe2  O3,  6.90%;  manganese,  Mn,  1.12%;  phosphorus,  P,  3.25%; 
alumina,  A12O3,  .97%;  lime,  CaO,  44.07%;  magnesia,  MgO,  8.04%.  The 
high  percentage  of  iron  oxides,  which  are  equivalent  to  approximately  24.0% 
metallic  iron,  gives  the  impression  that  the  process  is  wasteful  of  iron,  which 
is  true,  but  due  to  another  cause.  While  the  percentage  of  iron  oxide  is 
high,  it  does  not  exceed  that  of  the  run  off  slags  of  the  open  hearth  process, 
and  the  total  volume  of  slag  is  much  less  than  in  the  straight  open  hearth 
process,  so  that  the  loss  of  iron  here  is  perhaps  less  than  in  the  latter  process. 
The  chief  loss  is  at  the  converters,  and  there  can  be  no  doubt  but  that 
the  double  conversion  loss  exceeds  the  single  loss  in  the  straight  open  hearth 
process.  This  matter  assumes  its  chief  importance  as  it  relates  to  the 
conservation  of  the  iron  ore  supply. 


SECTION  III. 

COMBINATION   PROCESSES   IN  THE   SOUTH. 

The  Duplex  Process  in  the  South:  In  the  southern  district  the 
conditions  of  steel  manufacturing  are  very  different  from  those  in  the 
North,  and  many  additional  reasons  for  the  use  of  the  duplex  process  there 
are  to  be  found.  First,  in  the  South  there  is  no  pig  iron  that  is  suitable 
for  the  Bessemer  process  manufactured  there,  whereas,  in  the  North, 
Bessemer  iron  is  relatively  abundant.  Second,  there  is  no  low  phosphorus 
iron  or  spiegel  commercially  available  for  recarburizing  in  the  southern 
district  as  there  is  in  the  North,  and  this  lack  makes  it  necessary  in 
manufacturing  high  carbon  steels  in  the  South  to  catch  the  carbon  on  the 
way  down.  Third,  the  phosphorus  content  of  the  basic  iron  in  the  south- 
ern district,  which  averages  about  .80%,  is  very  high  as  compared  with 
the  phosphorus  content  of  basic  iron  in  the  North,  the  average  for  which 
is  about  .25%.  In  the  manufacture  of  high  carbon  steel  from  high  phos- 
phorus pig  iron  the  duplex  process  offers  exceptional  advantages  for  catch- 
ing the  carbon  high,  thus  reducing  the  amount  of  coal  or  coke-dust 
required  to  a  minimum  and  avoiding  rephosphorization  from  the  high 
phosphorus  slag.  Another  advantage  of  the  process,  when  iron  with  a 


298  TRIPLEX  PROCESS 


high  phosphorus  content  is  used,  is  that  it  permits  the  making  of  a  slag 
which  contains  a  high  percentage  of  phosphoric  acid  and  is  therefore  suit- 
able for  use  in  the  manufacture  of  fertilizers.  This  slag  is  a  valuable  by- 
product from  one  of  the  southern  plants. 

The  Southern  Triplexing  Process:  In  operating  the  duplex  process 
in  the  South,  it  has  been  found  that,  owing  to  the  high  phosphoric  acid 
content  of  the  slag,  it  is  difficult  to  prevent  the  reduction  of  some  of  the 
phosphorus  after  recarburizing.  This  rephosphorization  of  the  steel  occurs 
mainly  in  the  ladle,  particularly  in  the  portion  of  the  metal  in  direct  contact 
with  the  mass  of  floating  slag,  and  is  most  noticeable  in  the  last  two  or 
three  ingots  from  each  ladle  of  steel  teemed.  In  order  to  overcome  this 
defect  and  at  the  same  time  increase  the  production  of  basic  slag  for  phos- 
phate fertilizer,  one  plant  has  developed  a  triplex  process  in  which  two 
basic  open  hearth  units  are  required  to  finish  the  metal  after  blowing  in 
the  converter.  Briefly,  the  process  is  as  follows:  After  blowing,  the  metal 
is  transferred  from  the  converters  to  primary  basic  tilting  furnaces  where 
it  is  treated  with  lime  and  the  other  necessary  oxides  for  dephosphorizing 
it.  Here  the  phosphorus  content  in  the  metal  is  reduced  to  about  .07%, 
when  it  is  poured  into  ladles  and  transferred  by  specially  constructed,  heavy, 
extra-wide-gage  trucks  to  a  finishing  unit  composed  of  an  equal  number  of 
similar  furnaces.  In  these  furnaces  the  phosphorus  content  of  the  metal 
is  brought  below  .04%,  when  the  steel  is  finished  in  the  ladle  by  the  addition 
of  the  necessary  recarburizer  and  deoxidizers,  and  any  alloys  required  by 
the  specification.  It  is  said  that  this  process  does  not  reduce  the  capacity 
of  the  plant  and  materially  improves  the  uniformity  and  quality  of  the 
steel  produced. 


TESTING  OF  STEEL  299 


PART  II. 

THE  SHAPING  OF  STEEL. 
CHAPTER  I. 

THE  MECHANICAL  PROPERTIES  OF  STEEL. 

SECTION   I. 

SOME   GENERAL  REMARKS   PERTAINING  TO  THE  TESTING  OF  STEEL. 

The  Factors  that  Affect  the  Mechanical  Properties  of  Steel :  There 
are  four  factors  that  may  affect  the  quality  and  the  mechanical  properties 
of  steel;  namely,  the  method  of  manufacture,  or  refinement,  the  chemical 
composition,  the  mechanical  working  it  is  subjected  to,  and  the  heat  treat- 
ment it  receives.  The  first  of  these  factors  is  discussed  in  the  first  part 
of  this  book.  The  others  are  now  to  be  taken  up,  and  frequent  use  of  the 
terms  employed  in  the  mechanical  testing  of  steel  will  be  made  in  the  pages 
to  follow.  Hence,  although  in  the  natural  order  of  manufacturing  steel 
physical  tests  follow  the  shaping,  it  seems  well  to  take  up  this  subject  now 
in  order  that  the  reader  may  be  more  familiar  with  the  terms  employed 
in  connection  with  these  tests,  when  there  is  occasion  to  refer  to  them. 

The  Two  Objects  in  the  Testing  of  Steel:  In  the  early  days  it  was 
the  custom  to  order  steel  according  to  use,  that  is,  the  purchaser  asked 
the  steel  maker  for  a  certain  quantity  of  steel  suitable  for  a  certain  purpose, 
and  the  manufacturer  then  furnished  steel  of  a  kind  or  grade  he  considered 
most  suitable  for  the  purpose.  With  the  growth  of  the  steel  business,  this 
custom  proved  inadequate  to  the  conditions  and  was  superseded  by  the 
practice  of  ordering  steel  to  specifications,  which  appeared  to  be,  and  is, 
a  much  more  satisfactory  arrangement  for  all  parties  concerned.  The 
consumer  naturally  decided  that  he  should  know  better  than  anyone  else 
what  the  requirements  were,  and  the  manufacturer,  in  turn,  was  very  glad 
to  be  relieved  of  the  responsibility  he  assumed  under  the  old  system.  Now, 
the  only  basis  upon  which  the  consumer  of  steel  or  his  engineers  originally 
had  to  work  in  determining  specifications  was  experience.  Thus,  providing 
that  a  certain  steel  had  proved  satisfactory  for  a  certain  purpose,  he  desired 
for  the  new  work  steel  as  nearly  like  the  old  as  possible.  With  this  progress 
came  the  need  for  testing.  Then  as  undertakings  involving  the  use  of  steel 
increased  in  magnitude,  it  was  discovered  that  steels  made  by  the  same 
methods  are  subject  to  considerable  variation.  Furthermore,  in  order  to 


300  TESTING  OF  STEEL 


obtain  the  requisite  amount  of  steel,  it  is  often  necessary  to  use,  for  the 
same  purpose,  steels  made  in  different  ways.  And  again  the  need  for 
testing  was  felt  in  order  to  secure  uniformity  in  the  materials.  This 
testing  developed  along  two  lines,  namely,  physical  and  chemical. 

Relative    Importance   of    Physical   and    Chemical   Testing:     It   is 

evident  that,  to  the  consumer  of  steel,  its  mechanical  properties  are  of  first 
importance,  because  it  is  these  properties  that  determine  whether  or  not 
a  particular  steel  is  suitable  for  the  purpose  he  intends  it.  In  all  cases, 
then,  such  as  structural  steels,  in  which  the  material  is  put  in  service  as 
received  from  the  manufacturer,  the  customer  does  well  to  order  his  steel 
to  physical  specifications  only.  In  cases  where  the  steel  is  to  be  heat 
treated  or  is  to  undergo  other  treatment  in  the  hands  of  the  customer, 
then  it  should  be  ordered  to  a  chemical  specification  only.  Since  the  method 
of  manufacture  influences  the  properties  of  the  metal,  the  kind  of  steel, 
whether  Bessemer,  basic,  acid,  or  electric,  should  be  and  is,  usually,  specified. 
But  for  a  great  many  reasons,  for  a  discussion  of  which  time  and  space  are 
not  available,  it  is  unfair  to  ask  the  manufacturer  to  make  steel  to  order 
in  which  all  three  factors  are  specified.  Suffice  it  to  say,  that  in  the  one 
case  the  customer  should  be  satisfied  to  get  the  kind  of  steel  ordered  with 
the  required  physical  properties,  irrespective  of  the  means,  chemical  or 
otherwise,  which  the  manufacturer  may  have  found  it  necessary  to  employ 
in  order  to  supply  metal  with  the  properties  called  for.  In  the  other  case, 
the  purchaser  is  interested  only  in  obtaining  steel  properly  made  and  of 
the  proper  kind  and  composition,  because  with  such  steel  the  original 
physical  properties  will  be  replaced  by  new  ones  due  to  the  subsequent 
working  or  treatments.  From  the  view  point  of  the  consumer,  then,  the 
relative  importance  of  the  physical  and  the  chemical  test  depends  upon  the 
conditions  that  surround  each  individual  case.  But  to  the  manufacturer, 
chemical  testing  is  of  prime  importance,  because  it  offers  a  means  of  control 
whereby  he  is  able  to  produce  the  steel  with  a  greater  degree  of  certainty. 
For  a  description  of  the  methods  employed  in  chemical  testing  the  published 
standard  methods  of  the  Steel  Corporation  are  available. 

Nature  of  Physical  Testing:  It  should  at  all  times  be  borne  in  mind 
that  the  results  obtained  by  any  method  of  physical  testing  are  not  absolute, 
but  relative.  Obviously,  the  only  sure  test  is  actual  service,  and  it 
is  just  as  evident  that  such  tests  are  impracticable.  Therefore,  the  test 
must  be  carried  out  with  a  small  piece  of  material,  the  structure  and  con- 
dition of  which  are  likely  to  be  different  from  that  of  the  section,  taken  as 
a  whole,  from  which  it  was  cut.  A  second  objectionable  feature  is  found 
in  the  difficulty  of  subjecting  this  piece  to  the  same  conditions  that  it 
would  be  subjected  to  in  actual  service.  Attempts  have  been  made  to 
analyze  these  conditions  with  the  idea  of  classifying  the  forces  steel  is 
required  to  overcome  in  service,  so  that  in  testing  it  might  be  subjected 
to  the  same  kinds  of  forces.  With  respect  to  the  effect  they  tend  to  produce, 


PULLING  TEST  301 


forces  have  been  classified  as  (1)  tensional,  or  forces  tending  to  put  the 
material  under  tension,  that  is,  pull  it  asunder;  (2)  compressional,  or  forces 
that  tend  to  compress  the  piece  in  one  or  more  directions;  (3)  torsional,or 
forces  tending  to  twist  the  material;  and  (4)  shearing,  or  forces  that  tend 
to  cut  the  material  across  its  section.  With  respect  to  the  manner  in 
which  the  forces  are  applied,  the  following  classification  has  bean  made ; 
1.  Static  stresses,  which  are  the  result  of  the  gradual  application  of  a 
steady  or  constant  load.  2.  Fatigue  stresses,  such  as  result  from  the 
repeated  application  of  a  load  or  loads.  3.  Impact  stresses,  in  which  the 
metal  is  subjected  to  a  sudden  blow.  4.  Dynamic  stresses,  which  are 
repeated  impact,  or  vibratory  stresses. 

From  these  are  selected  the  class  of  force  or  stress  the  steel  is  likely 
to  be  required  to  withstand  in  service,  and  the  tests  will  be  arranged  accord- 
ingly. Added  to  these  are  a  number  of  miscellaneous  tests,  such  as  hardness 
tests  and  tests  to  determine  relative  resistance  to  wear  or  penetration. 


SECTION   II. 

THE  TESTING  OF  STRUCTURAL  AND  OTHER  SOFT  STEELS. 

The  Pulling  Test:  A  test  that  is  most  commonly  applied  to  steel, 
and  one  that  is  always  used,  and  almost  to  the  exclusion  of  all  others,  for 
testing  structural  steels,  is  that  commonly  spoken  of  as  the  pulling  test. 
As  the  name  implies,  the  chief  aim  in  this  test  is  the  determination  of  the 
tensile  strength  of  the  steel,  but  incidental  to  the  carrying  out  of  the  test 
much  additional  information  as  to  other  mechanical  properties  of  the 
sample  of  steel  is  obtained.  The  technical  terms  employed  in  testing  to 
indicate  these  properties  are  tensile  strength,  elastic  limit,  elongation, 
reduction  of  area,  and  modulus  of  elasticity.  The  exact  meaning  of  these 
terms  is  best  explained  in  connection  with  a  description  of  the  method  of 
making  the  test. 

Procuring  the  Test  Pieces:  Except  in  one  or  two  cases  where  it  is 
desirable  to  modify  the  usual  procedure,  the  test  piece,  or  sample,  is  sheared 
from  scrap  ends  cut  from  the  material  as  it  comes  from  the  rolls.  This 
piece  is  about  eighteen  inches  in  length  and  two  inches  in  width,  and, 
except  in  the  case  of  sheared  plates  from  which  both  longitudinal  and 
transverse  pieces  are  sometimes  taken,  its  long  axis  is  parallel  to  the 
direction  of  rolling.  As  a  rule,  the  test  piece  is  taken  from  a  position  not 
too  close  to  the  rolled  edge,  but  in  the  case  of  bars  of  small  sectional  area  the 
entire  section  of  the  proper  length  may  be  taken.  The  piece  is  then  stamped 
near  the  ends  with  the  heat  number  and  any  other  data  necessary  to 
identify  it. 


302  TESTING  OF  STEEL 


Preparation  of  the  Test  Piece:  The  working  or  shearing  of  the  test 
piece  puts  it  in  a  state  of  strain  and  produces  a  great  number  of  incipient 
cracks  on  the  edges,  so  that  if  it  were  pulled  in  this  condition  it  would 
fail  too  easily,  and  the  results  of  the  pulling  would  not  indicate  the  real  value 
of  the  properties  determined.  To  eliminate  these  cracks,  the  edges  of  the 
piece  are  milled  off  as  shown  in  the  accompanying  sketch,  and  the  milled 


S 


k—  -3"--*!        L  o,,    _  _*    V» 3/; --• 


18"     ---  --> 


Thickness  as  Rolled  Scale:  J"=l" 

Fig.  45.  Diagram  Showing  the  Usual  Form  of  the  Test  Piece  Used  in  Pulling 
Structural  Steels.  Occasionally  the  edges  are  milled  parallel  for  the  full  length 
of  the  specimen. 


edges  are  filed  smooth.  Then  if  the  piece  is  a  heavy,  thick  one  or  is  an 
alloy  steel,  such  as  nickel  steel,  it  is  allowed  to  rest  for  a  period,  the  length 
of  which  will  depend  upon  the  conditions  and  the  kind  of  steel.  This  resting 
is  necessary  to  allow  the  steel  to  relieve  itself  of  the  condition  of  strain 
which  the  working  has  set  up  in  it.  This  condition  seriously  affects  the 
ductility  of  the  steel,  as  is  shown  by  the  fact  that  some  test  pieces,  par- 
ticularly of  alloy  steels,  show  a  marked  improvement  in  elongation  after 
resting,  but  with  little,  if  any,  change  in  the  tensile  strength.  In  the  case 
of  soft  steels  of  moderate  thickness,  the  resting  period  is  not  so  important, 
as  the  working  does  not  produce  severe  strains,  and  such  steels  recover 
quickly  from  strains.  After  the  test  piece  has  been  machined  and  filed 
and  otherwise  made  ready  for  testing,  its  dimensions  are  taken.  From  a 
point  estimated  to  be  the  middle  of  the  machined  portion  of  the  piece, 
two  spaces  of  two  inches  each  are  laid  off,  with  a  double  pointed  punch, 
longitudinally  along  the  bar  and  in  both  directions  from  the  center  punch 
mark,  thus  making  a  distance  of  eight  inches  between  the  two  punch  marks 
that  are  the  farther  from  the  center  one.  This  space  fixes  the  length  of  bar 
that  is  later  to  be  the  basis  for  calculating  the  percentage  of  elongation. 
Finally,  with  screw  micrometers  the  width  and  thickness  of  the  test  piece 
are  taken  and  recorded.  A  careful  operator  will  measure  these  dimensions 
in  three  or  four  places  to  determine  to  what  extent  they  are  uniform.  The 
test  piece  is  then  ready  to  be  pulled. 


PULLING  TEST  303 


Pulling  the  Test:  The  testing  machine  may  be  likened  to  a  beam 
scale  or  weighing  machine,  and  if,  instead  of  lying  upon  the  platform  of  the 
scale,  the  test  piece  be  thought  of  as  being  attached  by  one  of  its  ends 
under  the  platform  with  its  other  end  free  for  the  attachment  of  some 
device  for  exerting  a  vertical  pull,  the  analogy  is  almost  exact.  In  modern 
machines  the  pulling  device  is  either  an  electric  motor,  attached  through 
gears  and  screws  to  a  gripping  device  that  clamps  one  end  of  the  test  piece, 
or  an  hydraulic  ram  connected  directly  with  the  clamping  device.  With 
such  an  arrangement  the  amount  of  the  pull  is  registered  in  pounds  on  the 
graduated  beam  of  the  machine.  This  beam  is  provided  with  a  travelling 
weight,  which,  by  means  of  a  screw  and  worm  drive  actuated  by  hand, 
may  be  rolled  out  along  the  beam  as  the  pull  increases,  thus  keeping  the 
beam  in  the  neutral  position  and  registering  the  amount  of  the  tension  at 
all  stages  of  the  pull.  When  the  test  has  been  properly  marked  and 
measured,  it  is  placed  in  the  machine  in  a  vertical  position  and  securely 
clamped  in  the  gripping  boxes,  or  shackles.  Then,  the  pulling  device  is 
started  at  low  speed,  and  the  weight  is  cautiously  moved  out  along  the  beam, 
the  operator  keeping  it  in  a  perfectly  horizontal  position  with  the  free  end 
midway  between  the  upper  and  lower  beam-end  stops.  The  continued 
action  of  the  pulling  machine  is  an  indication  that  the  test  piece  is  stretching 
slightly.  That  such  is  actually  the  case  could  be  proved  by  stopping  the 
machine  and  measuring  with  delicate  instruments  the  distance  between 
the  two  extreme  space  marks  and  comparing  this  measurement  with  the 
original  length.  As  the  pulling  is  continued  uniformly,  the  beam  weight 
is  advanced  at  a  uniform  rate,  indicating  that  the  piece  is  obeying  the  law 
of  stress  and  strain;  but  a  point  is  soon  reached  where  the  beam  suddenly 
drops,  indicating  that,  without  any  increase  in  the  load,  there  has  been  a 
sudden  increase  in  the  length  of  the  test  piece.  In  testing  parlance  this 
point  is  called  the  elastic  limit,  the  yield  point,  or  the  point  of  permanent 
set.  To  be  accurate,  the  point  reached  immediately  before  this  sudden 
stretch,  or  give,  occurs  marks  the  true  elastic  limit,  while  the  drop  of 
the  beam  marks  the  yield  point.  A  reading  of  the  weight  indicated  by 
this  position  of  the  beam  weight  is  therefore  taken,  and  the  pulling  is  con- 
tinued as  before,  with  the  exception  that  the  speed  of  the  pull  may  be 
increased  somewhat.  As  the  beam  rises  again,  it  is  necessary  to  advance 
the  beam  weight  much  more  rapidly  than  before,  which  fact  indicates  a 
more  rapid  stretching  of  the  test.  In  a  short  time  another  point  is  reached 
where  the  beam  suddenly  drops  for  the  second  time,  but  here,  though  the 
pulling  is  continued,  the  beam  will  not  rise  again.  A  second  reading  is 
therefore  made,  and  the  weight  recorded  is  taken  as  a  measurement  of  the 
tensile  strength  of  the  test  piece.  Finally,  as  the  machine  continues  to 
elongate  the  specimen,  the  point  of  rupture  is  reached,  and  the  piece  breaks 
apart.  In  practice  no  reading  is  taken  at  the  breaking  point,  but  if  it  were, 
it  would  be  necessary  to  reverse  the  direction  of  motion  of  the  beam  weight, 


304 


TESTING  OF  STEEL 


because  the  breaking  load  is  generally  less  than  the  tensile  strength. 
The  latter,  therefore,  is  usually  referred  to  as  the  ultimate  strength, 
maximum  stress,  or  maximum  load. 

Graphic  Representation  of  Tests :  The  pulling  of  a  test  is  admirably 
illustrated  by  means  of  a  graph,  which  is  also  a  great  aid  in  understanding 
the  relations  of  the  various  terms  employed  in  designating  the  points 
described  above.  The  following  graph,  while  not  absolutely  accurate  and 
to  scale  in  some  of  its  parts,  will  serve  to  illustrate  the  scheme  for  preparing 
graphs  and  to  make  clearer  the  description  of  the  pulling  of  the  test  piece. 
The  diagram  requires  no  explanation. 


75000 


70000  - 


0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23 
Elongation  in  tenths  of  an  inch 

FIG.  46.  Graph  Representing  the  Pulling  of  a  Structural  Steel  Test  Piece. 

Reasons  for  the  Points  of  Yield  and  Maximum  Stress:     No  very 
satisfactory  reason  for  the  occurrence  of  the  yield  point  has  yet  been 


PULLING  TEST  305 


advanced.  Some  think  that  it  is  due  to  some  rearrangement  of  the  mole- 
cules. Again,  grain  structure  may  be  the  cause.  Since  steel  is  made  up 
of  small  grains  or  crystals,  it  appears  reasonable  to  suppose  that  they  have 
at  the  time  of  their  formation  assumed  a  form  and  an  arrangement  that  is 
most  natural,  and  that  they  will  offer  resistance  to  any  force  tending  to 
change  this  form  or  arrangement.  This  resistance  is  made  up  of  two  forces 
of  attraction,  namely,  one  that  tends  to  keep  the  grains  in  contact  and 
another  that  tends  to  preserve  the  arrangement  of  the  molecules  within 
the  grain.  At  the  elastic  limit  this  resistance  is  just  balanced  by  the 
tension,  but  under  any  greater  tension,  deformation  of  the  grains  begins, 
and  the  structure  "gives"  suddenly,  becoming  at  the  same  time  longer  and 
smaller  in  cross  section.  Up  to  the  elastic  limit  the  slight  stretch  may 
be  due  to  a  partial  rearrangement  of  the  grains.  When  the  tension  is 
removed  the  natural  arrangement  is  restored,  with  the  result  that  the 
piece  immediately  assumes  its  initial  form  and  size.  When  subjected  to 
tension  under  this  limit  the  body  remains  in  an  elastic  condition,  and  the 
deformation  it  undergoes  is  called  elastic  deformation.  Above  the  yield 
point  the  grains  are  undergoing  deformation,  that  is,  they  are  in  a  way 
destroyed,  and  the  piece  of  metal  reacts  more  like  a  plastic  than  an  elastic 
body.  Therefore  the  body  is  said  to  be  undergoing  plastic  deformation. 
This  change  in  grain  form  is  continuous,  and  requires  an  ever-increasing 
force,  or  stress,  to  make  it  so.  The  condition  is  strictly  analogous  to  cold 
working,  which  will  be  discussed  later.  Consequently,  the  piece  becomes 
stronger,  but  at  the  same  time  it  is  becoming  longer  and  correspondingly 
smaller  in  cross  section.  Ultimately,  as  the  necking  of  the  piece  becomes 
pronounced,  the  loss  in  strength  due  to  the  decreased  area  of  the  section, 
plus  the  external  stress  applied,  balances  and  then  exceeds  the  maximum 
stress  that  the  cold  working  can  develop.  From  this  point,  then,  the 
external  force  necessary  to  balance  the  forces  of  attraction  between  the 
grains  becomes  less  and  less  as  the  area  continues  to  decrease  rapidly. 
Finally,  the  maximum  deformation  of  the  grains  is  reached,  when,  if  the 
tension  applied  externally  exceeds  the  forces  of  attraction  tending  to  keep 
the  grains  together  at  the  point  of  least  cross  sectional  area,  the  piece  is 
fractured  at  that  point. 

Examination  of  Test  After  Pulling:  After  fracture  the  two  parts  of 
the  test  piece  are  removed  from  the  machine,  and  the  fractured  ends  are 
fitted  together  as  neatly  as  possible  for  the  measurements  to  follow.  The 
distance  between  the  extreme  punch  marks  is  now  measured.  The  difference 
between  this  distance  and  the  original  space  of  eight  inches  gives  the  elon- 
gation for  the  piece,  which  is  properly  recorded.  An  examination  of  the 
piece  shows  that  while  it  has  been  reduced  in  section  throughout  its  length, 
the  reduction  is  most  pronounced  in  the  region  of  the  fracture,  where  the 
piece  underwent  the  characteristic  deformation  known  as  necking  before  it 
broke.  It  is  here,  as  near  to  the  fractured  ends  as  possible,  that  the  width 
and  thickness  are  again  measured  in  order  to  ascertain  the  reduction  in 


306  TESTING  OF  STEEL 


area.  Finally,  the  fractures  are  designated  as  angular,  cup-shaped,  half 
cup,  and  irregular.  Very  little  importance  can  be  attached  to  the  form 
of  the  fracture,  but  some  inspectors  believe  that  the  cup  shaped  fracture 
indicates  more  nearly  perfect  uniformity  in  the  material  than  the  other 
forms. 

Calculating  the  Results  of  the  Test:  The  results  obtained  in  the 
test  are  for  the  given  piece  only,  and,  in  order  that  the  results  from  different 
tests  may  be  comparable,  they  must  be  calculated  to  a  common  basis. 
Tensile  strength  and  elastic  limit  are  always  expressed  in  pounds  per  square 
inch  in  the  United  States,  in  tons  per  square  inch  in  England,  and  kilograms 
per  square  millemeter  in  France  and  other  countries  using  the  metric 
system.  The  elongation  is  expressed  as  the  percentage  of  increase  on  the 
original  length  of  the  bar.  In  the  United  States  this  length  for  structural 
and  other  low  carbon  steels  is  usually  eight  inches,  as  formerly  stated,  but 
other  lengths,  as  ten  and  twelve  inches,  ten  centimeter,  etc.,  may  be  used. 
For  this  reason  it  is  always  important  that  the  original  length  of  the  bar 
be  stated,  as  the  percentage  of  reduction  on  two  inches,  for  example,  would 
be  much  greater  than  that  based  on  eight  inches  because  of  the  pronounced 
local  contraction,  or  necking,  at  the  point  of  fracture.  This  variation  in 
the  length  of  test  pieces  is  made,  because  the  relation  between  the  length 
and  the  thickness  of  the  test  affects  the  elongation.  Hence,  in  order  that 
tests  of  different  thicknesses  may  be  comparable,  the  ratio  between  the 
thickness  and  length  is  kept  constant  by  varying  the  length.  The  ideal 
thickness  for  a  length  of  eight  inches  is  about  three-fourths  inch.  Over  or 
under  this  thickness,  the  specification  is  usually  modified  either  by  chang- 
ing the  length  or  by  making  the  proper  allowance  from  the  elongation  as 
determined.  The  reduction  of  area  is  expressed  in  percentage  contraction 
of  area  of  the  cross  section  as  compared  with  the  original  area  of  the  cross 
section.  An  example  will  serve  to  clear  up  any  doubtful  points  that  may 
not  have  been  made  clear  in  this  explanation. 


Table  46.    Data  on  the  Pulling  Test  Represented  by  the  Graph 

of  Fig.  46. 

Dimensions  of  Piece 
Before  Pulling  After  Pulling 

Length iV  ,,.,„.     8.0     inches  10.20  inches 

Width 1.41        "  1.00      " 

Thickness : 860      "  .60      " 

Area 1.213  sq.  in.  .60  sq.  in. 

Readings  on  pulling  bar:    Elastic  limit=44600  Ibs. ;  Ultimate  strength= 
74600  Ibs. 


PROPERTIES  DETERMINED 


307 


Calculations: 

Elastic  Limit 

Ultimate  Strength 
Elongation 


44,600 
1.213 

74,600 
1.213 

10.20—8 


=    36770-lbs.  per  sq.  in. 
=    61500-   "       "        " 
=    27.5%  in  8  inches 


Reduction  of  Area     = 


91  Q  r  ^  An 
-  '-  —  • 
1.213 


=    50.5% 


The  Modulus  of  Elasticity,  or  Young's  Modulus:  The  Modulus  is 
seldom  determined  in  practical  work,  as  it  involves  the  determination  of 
the  absolute  increase  in  length  of  the  test  bar  up  to  the  elastic  limit,  which 
is  a  quantity  so  small  as  to  be  very  difficult  to  determine  accurately.  It 
may  be  defined  as  that  force,  expressed  in  pounds,  tons,  or  kilograms  per 
unit  of  cross  section  area,  that  would  stretch  a  test  piece  to  twice  its  original 
length,  when  applied  to  one  end  of  it  and  acting  in  the  direction  of  its  length. 

It  may  be  found  by  applying  the  following  formula:    M= where  M= 

Ax  1 

modulus  of  elasticity,  f=force  applied,  L=original  length,  A=original 
sectional  area,  l=increase  in  length.  For  low  carbon  steel  Young's  Modulus 
is  about  29,000,000  Ibs. 

Relative  Importance  of  the  Mechanical  Properties  as  Determined 
by  the  Pulling  Test:  From  what  has  been  said  it  is  plain  that  the 
quantities  that  may  be  taken  as  indicative  of  the  strength  of  the  material 
are  tensile  strength  and  elastic  limit;  but  while  most  engineers  will  insist 
on  both  tensile  strength  and  elastic  limit  being  given  and  a  few  are  content 
to  get  the  tensile  strength  only,  it  is  evident  that,  in  its  practical  application, 
the  elastic  limit  will  determine  the  working  strength  of  the  steel,  that  is, 
the  maximum  load  a  given  piece  may  carry  with  safety.  In  the  elastic 
range  the  body  stretches  and  recovers  with  increase  and  decrease  in  the 
load;  in  the  plastic  range  it  cannot  recover  but  continues  to  elongate 
as  long  as  tensional  stresses  are  applied,  and  in  this  condition  it  is  a  very 
unsafe  material  to  use.  The  percentage  reduction  of  area  and  the  percentage 
of  elongation  are,  when  considered  together,  an  index  of  the  ductility  of 
the  metal,  for  both  are  required  to  give  an  idea  of  the  amount  of  the 
deformation  before  rupture.  However,  engineers  are  divided  in  their 


308  TESTING  OF  STEEL 


opinions  as  to  the  relative  importance  of  the  two  factors.  In  a  general 
way,  it  may  be  stated  that  the  reduction  of  area  is  regarded  as 
more  reliable  than  elongation,  because,  as  previously  explained,  the  quantity 
denoting  the  latter  is  affected  by  the  ratio  of  the  length  of  the  test  piece 
to  its  cross  sectional  area.  In  many  foreign  countries  this  ratio  is  always 
specified. 

Bending  Tests:  On  certain  classes  of  material,  bending  tests  are  made 
in  addition  to  the  pulling  test.  These  tests,  simple  in  character,  consist 
merely  in  bending  test  pieces  similar  to  those  used  for  pulling,  and  similarly 
prepared,  through  certain  specified  arcs.  The  bending  is  usually  on  cold 
material,  but  some  orders  call  for  hot  bending  tests,  also.  Such  tests  are 
employed  to  make  sure  that  the  steel  is  not  cold  short  or  hot  short  and, 
in  a  way,  to  indicate  the  ductility  of  the  metal. 


SECTION  III. 

THE  TESTING   OF  THE   HIGHER   CARBON   AND    HEAT  TREATED    STEELS. 

Kinds  of  Tests  Applied  to  the  Higher  Carbon  and  Heat=treated 
Steels :  For  testing  the  class  of  material  referred  to  under  this  heading, 
a  large  number  of  different  tests  have  been  devised.  These  tests  may  be 
classified  under  the  headings  of  tensile  tests,  compressive  tests,  torsional 
tests,  impact  tests,  and  hardness  tests.  Of  these,  the  tensile,  impact,  and 
hardness  tests  are  the  ones  most  frequently  met  with,  and  will,  therefore, 
be  described  later.  Of  the  others  the  torsional  test  is  perhaps  the  most 
important,  as  it  is  largely  used  in  the  testing  of  steel  for  automobiles. 
It  consists  in  twisting  a  small  round  specimen  of  steel  held  in  a  suitable 
machine  until  rupture  occurs.  In  it  a  test  piece  of  standard  size  is  used, 
and  values  for  this  piece  corresponding  to  the  elastic  limit  and  ultimate 
strength,  but  expressed  in  inch-pounds,  are  obtained  very  much  as  in  the 
tension  test;  the  amount  of  distortion,  however,  is  given  in  degrees.  The 
compression  test  is  carried  out  by  means  of  a  machine  similar  in  con- 
struction to  the  pulling  machine.  The  test  piece  may  be  in  the  form  of 
a  small  cylinder  or  a  one  inch  cube.  The  elastic  limit  under  compression 
is  determined,  and  the  distortion  is  indicated  by  the  decrease  in  length. 

The  Tensile  Test:  The  test  for  determining  the  tensile  strength  of 
the  higher  carbon  and  heat  treated  steels  is  carried  out  in  a  manner  similar 
to  that  for  the  softer  steels,  but  since  the  material  is  so  much  stronger  and 
the  items  made  from  such  steels  do  not  lend  themselves  to  the  same  method 
of  sampling,  the  test  piece  is  much  smaller  than  that  employed  in  the  case 
of  structural  steels.  This  specimen  is  in  the  form  of  a  small  round,  as 


HIGH  TENSILE  STEELS 


309 


shown  in  the  accompanying  figure,  and  is  often  obtained  by  boring  with 
a  hollow  drill  about  midway  between  the  center  and  outside  surface  of 
the  section  sampled. 


2i" 
4" 


FIG.  47.  Drawing  Showing  Usual  Size  and  Form  of  Test  Piece  Used  in  Pulling  High 
Tensile  Steels.  The  ends  may  be  of  any  form  desired  but  the  central  machined 
portion  must  be  as  shown  in  the  figure. 

I  mpact  Test :  While  several  different  types  of  machines  for  measuring 
the  resistance  of  steel  to  impact  have  been  invented,  the  results  obtained 
with  any  of  these  machines  so  far  have  not  been  considered  very  reliable, 
as  widely  varying  results  may  be  obtained  on  the  same  steel  tested  on 
the  same  machine.  In  practice,  therefore,  the  nearest  approach  to  an 
impact  test  is  what  is  commonly  and  correctly  called  the  drop  test.  It 
is  applied  to  full  size  pieces  of  rails,  to  axles,  and  to  other  sections.  It 
consists  in  allowing  a  specified  weight  to  drop  from  a  specified  height  a 
specified  number  of  times  upon  the  sample,  which  is  supported  at  two  points 
on  a  heavy  anvil  or  block  resting  upon  strong  springs.  All  three  of  these 
factors  may  vary  greatly  with  different  classes  of  material  and  with  the 
different  ideas  of  the  engineers.  While  it  does  not  measure  absolutely 
any  property  of  the  metal  and  is  to  be  considered  as  comparative  or 
qualitative  only,  it  is,  nevertheless,  one  of  the  most  useful  of  practical  tests, 
for  it  determines,  in  a  crude  way,  the  ductility  and  homogeneity  of  the  metal 
and  its  resistance  to  shock.  In  the  case  of  axles,  and  other  round  bodies, 
the  deflection  from  a  given  weight  may  be  kept  constant  for  different  sizes 
by  varying  the  height,  for  since  the  strength  of  such  a  section  varies  as 
the  cube  of  the  diameter,  for  equal  deflections,  the  height  varies  as  the 
cube  of  the  diameter  of  the  specimen  at  its  center. 

Hardness  Tests:  The  best  known  and  the  most  widely  used  instru- 
ments for  measuring  the  hardness  of  metals  are  the  Shore  scleroscope  and 
the  Brinell  ball  testing  machine.  The  Shore  instrument  consists  of  a  small 
diamond-faced  tup  enclosed  in  a  glass  tube  which  is  provided  with  a  suction 
bulb,  whereby  the  tup  may  be  raised  to  the  top  of  the  tube  and  dropped  from 
a  definite  and  fixed  height.  To  make  a  determination,  the  instrument  is 


310  TESTING  OF  STEEL 


held  in  the  vertical  position  with  the  lower  end  resting  upon  a  smooth 
and  highly  polished  spot  on  the  surface  of  the  metal  to  be  tested,  when 
the  tup  is  allowed  to  drop  by  compressing  the  bulb.  The  height  of  the 
rebound,  which  may  be  read  on  a  scale  inscribed  on  the  tube,  is  taken  as 
a  measurement  of  the  hardness.  Notwithstanding  the  fact  that  the  results 
obtained  by  this  instrument  are  sometimes  very  erratic,  especially  if  the 
surface  of  the  different  spots  tested  have  not  been  properly  and  uniformly 
polished,  it  is  a  valuable  instrument  for  comparing  the  surface  hardness 
of  different  parts  of  a  body  that  is  too  large  to  be  tested  in  any  other 
way.  It  also  possesses  the  advantage  that  the  tests  may  be  made  upon 
the  finished  article  without  injury  to  the  article  itself. 

Brinell  Hardness:  The  Brinell  hardness  test  measures  the  ability  of 
the  metal  to  resist  penetration  by  a  small  ball  when  propelled  by  a  gradually 
applied  force.  It  consists  in  pressing  a  hardened  steel  ball  into  the  surface 
of  the  specimen  under  test  by  means  of  a  fixed  load  gradually  applied. 
The  instrument  consists  essentially  of  a  small  hydraulic  press,  which  is 
operated  by  a  small  hand  pump  and  is  provided  with  a  pressure  gauge 
for  reading  the  pressure,  and  a  special  contrivance  for  automatically 
holding  the  pressure  when  it  has  reached  a  maximum  of  3000  kilograms. 
The  piston  of  the  press,  which  acts  vertically  downward,  is  provided 
on  its  end  with  a  hardened  steel  ball,  ten  millimeters  in  diameter,  by 
means  of  which  an  impression  may  be  made  on  the  smooth  surface  of  the 
specimen,  which  rests  on  a  firm  but  an  adjustable  base.  The  operation  of 
the  instrument  is  very  simple.  The  specimen,  the  surface  of  which  has  been 
planished  with  a  file,  a  whetstone,  emery  wheel  or  similar  means,  is  laid  on 
the  base  and  is  then  brought  in  contact  with  the  ball  by  turning  a  small 
wheel  for  adjusting  the  base,  or  platform.  By  operating  the  hand  pump 
until  the  maximum  pressure  is  attained  and  maintained  for  about  one 
half  minute,  the  steel  ball  is  pressed  into  the  surface;  then  the  pressure 
is  relieved,  the  base  is  lowered,  and  the  diameter  of  the  impression 
made  in  the  specimen  is  measured  by  means  of  a  microscope  fitted 
with  a  millimeter  scale,  vernier,  and  cross  hair.  From  this  diameter  the 
spherical  area  of  the  impression  may  be  calculated,  which,  divided  into  the 
maximum  load  of  3000  kilograms,  gives  the  hardness  number.  The  formulas 
for  making  these  calculations  may  be  combined  into  a  single  formula,  thus : 


H=- 


where  P=3000  Kilograms  pressure,  r=5  mm.,  radius  of  the  ball,  D=diameter 
of  the  impression,  and  H=the  hardness  number.  In  practice  it  is  most 
convenient  to  have  a  table,  such  as  that  shown  below,  prepared,  from 
which  the  number  may  be  obtained  direct  from  the  diameter  of  the 
impression. 


BRINELL  TEST 


311 


Relation  of  Brinell  Number  to  Tensile  Strength:  It  is  both  a 
curious  and  a  significant  fact  that  the  Brinell  hardness  number  bears  a 
close  relation  to  the  ultimate  strength,  as  may  be  seen  from  an  inspection 
of  the  following  table,  which  was  prepared  only  after  comparing  results 
obtained  upon  thousands  of  specimens,  to  which  both  the  Brinell  and  the 
pulling  tests  had  been  applied.  This  relation,  it  will  be  observed,  is 
approximately  500,  and  holds  for  all  grades  of  carbon  steel  whether  they 
be  heat  treated  or  in  their  natural  state  as  forged  or  rolled.  For  this 
reason  the  Brinell  test  is  applicable  to  the  rapid  testing  of  steel  from  which 
samples  for  the  tensile  test  cannot  be  obtained. 

Table  47.     Brinell  Hardness  Numbers  and  Estimated  Tensile  Strength 
for  3000  Kilogram  Pressure  on  a  10  MM.  Ball  Testing  Machine. 


Diam. 
of  Im- 
pression 
in  m/m 

Hard- 
Number 

Ultimate 
Pounds 
per  Sq.  In. 

Diam. 
of  Im- 
pression 
in  m/m 

Hard- 
ness 
Number 

Ultimate 
Pounds 
per  Sq.  In. 

Diam. 
of  Im- 
pression 
in  m/m 

Hard- 
ness 
Number 

Ultimate 
Pounds 
per  Sq.  In. 

2.00 

946 

465100  ;;  3.35 

332 

162700 

4.70 

163 

80100 

2.05 

878 

442100 

3.40 

321 

157800 

4.75 

159 

78300 

2.10 

857 

421600 

3.45 

311 

153100 

4.80 

156 

76600 

2.15 

817 

402000  ij  3.50 

302 

148600 

4.85 

153 

74900 

2.20 

782 

383700  i  3.55 

293 

144300 

4.90 

149 

73300 

2.25 

744 

366600    3.60 

286 

140200 

4.95 

146 

71700 

2.30 

713 

350600   |  3.65 

277 

136200 

5.00 

143 

70200 

2.35 

683 

335700    3.70 

269 

132400 

5.05 

140 

68700 

2.40 

652 

321600    3.75 

262 

128800 

5.10 

137 

67200 

2.45 

627 

308400  I  3.80 

255 

125300 

5.15 

134 

65800 

2.50 

600 

295900  1   3.85 

248 

121900 

5.20 

131 

64500 

2.55 

578 

284300 

3.90 

241 

118700 

5.25 

128 

63100 

2.60 

555 

273300 

3.95 

235 

115500 

5.30 

126 

61800 

2.65 

532 

262900 

4.00 

228 

112600 

5.35 

124 

60600 

2.70 

512 

253100 

4.05 

223 

109700 

5.40 

121 

59400 

2.75 

495 

243800 

4.10 

217 

106900 

5.45 

118 

58200 

2.80 

477 

235000 

4.15 

212 

104200 

5.50 

116 

57000 

2.85 

460 

226600 

4.20 

207 

101600 

5.55 

114 

55900 

2.90 

444 

218700 

4.25 

202 

99100 

5.60 

112 

54800 

2.95 

430 

211200 

4.30 

196 

96700 

5.65 

109 

53700 

3.00 

418 

204100 

4.35 

192 

94400 

5.70 

107 

52700 

3.05 

402 

197300 

4.40 

187 

92200 

5.75 

105 

51700 

3.10 

387 

190800 

4.45 

183 

90000 

5.80 

103 

50700 

3.15 

375 

184600 

4.50 

179 

87900 

5.85 

101 

49700 

3.20 

364 

178800 

4.55 

174 

85800 

5.90 

99 

48800 

3.25 

351 

173200 

4.60 

170 

83900 

5.95 

97 

47900 

3.30 

340 

167800 

4.65 

166 

82000 

Pressure 


=Hardness  Number. 


Area  of  Impression 

Tensile  in  Kg.  per  Sq.  MM.=Coefficient  .346  x  Hardness  Number. 

Factor  to  Convert  Kg.  per  Sq.  M/M  to  Lbs.  per  Sq.  In.=1422.3 


312  MECHANICAL  TREATMENT 


CHAPTER  II. 

THE  MECHANICAL  TREATMENT  OF  STEEL. 

SECTION   I. 

METHODS   AND   EFFECTS   OF   MECHANICALLY   WORKING    STEEL. 

Methods  of  Shaping  Steel:  After  the  separation  of  the  metal  from 
its  ores,  which  in  modern  practice  is  accomplished  by  means  of  either  the 
blast  furnace  or  a  form  of  electric  furnace,  and  its  purification  in  the 
Bessemer  converter,  open  hearth,  puddling  furnace,  or  electric  furnace,  the 
third  step  in  the  metallurgy  of  iron  is  the  reduction  of  the  large  bodies 
of  metal  thus  produced  to  the  various  forms  and  sizes  required  by  the 
many  uses  to  which  it  is  to  be  put.  In  general  this  shaping  may  be  brought 
about  either  by  pouring  the  metal  while  in  a  molten  state  into  moulds, 
which  act  is  called  casting,  or  by  mechanically  working  it.  Since  by  all 
the  methods  of  purification,  puddling  excepted,  the  metal  is  obtained  in 
the  fluid  state,  casting  would  appear  to  be  the  simplest  and  cheapest 
method  of  shaping;  but  for  forming  articles  of  very  small  section,  it  is 
evident  that  this  method  is  impracticable;  nor  is  it  used,  unless  unavoid- 
able, to  form  the  larger  sections  in  which  the  mechanical  properties  of  the 
metal  must  be  developed  to  the  highest  degree.  Some  shapes  on  account 
of  their  size  or  their  intricate  design  require  casting,  while  others  are  cast 
because  they  require  no  great  strength  in  service  and  the  cost  of  production 
only  is  to  be  considered.  A  lack  of  strength  and  ductility  in  castings  is 
inherent,  and  is  due  to  chemical  and  physical  phenomena  that  accompany 
the  solidification  of  the  molten  metal,  something  about  the  nature  of  which 
will  be  explained  later  in  connection  with  the  cooling  of  ingots.  Suffice  it 
to  say  now  that  the  weakness  of  castings  is  due  chiefly  to  any  or  all  of 
three  causes,  namely,  blow  holes,  segregation,  and  crystallization. 

Benefits  of  Mechanical  Working:  On  the  other  hand,  mechanical 
shaping  improves  the  quality  of  the  metal  by  forcing  its  particles  into 
more  intimate  contact,  closing  up  cavities,  and  by  refining  its  crystalline 
structure,  and  so  has  important  functions  aside  from  the  mere  reduction 
to  form  and  size.  The  change  in  properties  that  may  be  attributed  to  the 
process  of  mechanical  working  is  a  marked  one,  for  the  strength,  ductility 
and  hardness  are  all  affected.  Of  these  properties  the  strength  is  always 
increased  by  the  working,  the  hardness  may  or  may  not  be  markedly 
increased,  while  the  ductility,  i.  e.,  elongation  and  reduction  in  area,  may 
be  either  increased  or  decreased,  depending  on  the  conditions  of  the 
working.  The  amount  of  change  in  each  of  these  properties  for  a  given 
steel  of  a  certain  chemical  composition  is  affected  by  the  amount  of  work 
done  and  by  the  temperature  at  which  the  working  is  carried  on. 


HOT  AND  COLD  WORKING  313 

Hot  and  Cold  Working:  In  the  mechanical  treatment  of  the  metal, 
the  first  distinction  to  be  made  is  that  of  hot  and  cold  working.  The 
study  of  metallography  has  shown  that  the  term  hot  working  of  steel  should 
be  applied  to  the  working  of  it  at  temperatures  above  its  upper  critical 
range,  the  temperature  of  which  varies,  inversely  with  the  carbon  content, 
from  700°  to  900°  C.,  while  all  work  done  at  temperatures  below  this 
range  should  be  called  cold  working.  It  will  be  shown  in  the  next  part  of 
this  book  that  a  sharp  change  in  structure  due  to  working  takes  place  as 
the  critical  temperature  of  the  steel  is  passed.  This  change  is  due  mainly 
to  the  fact  that  above  this  range  iron  exists  in  an  allotropic  crystalline 
form,  the  gamma  form,  in  which  carbon  dissolves  to  form  a  homogeneous 
mixture,  while  below  it  the  metal  assumes  the  alpha  form  and  is  a  crystal- 
lized aggregate  of  ferrite  and  cementite.  A  metallographic  examination 
of  specimens  shows  that  the  result  of  working  this  aggregate  structure  is 
one  of  permanent  distortion,  or  strain,  and  one  in  which  the  properties  of 
the  metal  are  deeply  affected,  as  indicated  by  the  different  physical 
tests.  The  elastic  limit,  tensile  strength,  and  hardness  are  increased, 
while  the  ductility  is  reduced.  The  extent  of  this  change  varies  according 
to  the  temperature,  and  is  most  marked  when  the  working  is  done 
at  or  below  atmospheric  temperatures.  Cold  working  becomes  less 
effective  as  the  critical  temperature  is  approached,  which  is  due  to  the 
increase  in  molecular  energy  and  the  resulting  loss  of  rigidity  by  the  solid. 
It  should  be  noted  that  below  the  critical  range  no  refinement  of  the  granular 
structure  can  be  accomplished  by  working.  In  hot  working,  the  grain  size 
is  decreased,  and  the  metal  is  subject  otherwise  to  mechanical  refinement, 
the  extent  of  which  depends  not  only  on  the  amount  of  work  done  and  size 
of  the  section  but  on  the  temperature  above  the  critical  range  at  which 
the  work  is  finished.  However,  if,  after  a  working,  the  metal  be  heated 
above  this  finishing  temperature,  as  is  often  the  case  in  the  actual  rolling 
of  steel,  the  grain  refinement  of  the  previous  working  may  be  partly  or  entirely 
destroyed,  depending  upon  the  temperature  to  which  the  piece  is  reheated. 
Owing  to  the  plasticity  of  the  metal  at  the  higher  temperatures,  the  dis- 
tortion due  to  working  above  the  critical  range  does  not  produce  a  per- 
manent strain  in  the  structure  of  the  solid.  After  each  distortion  the 
structural  components,  the  crystals  or  grains,  are  free  to  return  to  the  shape 
and  arrangement  peculiar  to  their  state  of  equilibrium.  Besides,  since  the 
steel  takes  on  a  new  structure  and  a  new  condition  is  born  upon  cooling 
through  the  critical  range,  any  internal  tension  set  up  by  the  working 
is  relieved  by  the  rearrangement  that  takes  place  in  passing  through  this 
range.  This  fact  gives  another  reason  for  the  superior  quality  of  hot 
worked  material  over  castings,  which  are  subject  to  immense  internal 
tension,  or  stresses,  set  up  by  physical  phenomena  that  accompany  the 
solidification  and  by  the  forces  of  contraction  due  to  the  unequal  rates  of 
cooling  between  the  exterior  and  interior  of  a  casting.  Such  severe  stresses 
do  not  occur  in  hot  worked  material.  Referring  to  the  more  common  prac- 


314 


MECHANICAL  TREATMENT 


« 


1.  Cast  steel.  Carbon  .35  per  cent.   Magnified    100 
diameters. 


3.  Cold  worked  hypo-eutectoid  steel.      Carbon  0.30 
per  cent.     Magnified  100  diameters. 


FIG.  48.  Showing  Effects  of  Working 


HOT  AND  COLD  WORKING 


315 


2.  Hot  worked  steel.   Carbon  0.50  per  cent.   Finishing 
temperature  high.     Magnified  100  diameters. 


4.  Hot  worked  steel.     Carbon  0.50  per  cent.     Fin 
ishing  temperature  low.     Magnified  100  diameters 


upon  the  Grain  Structure  of  Steel. 


316  METHODS  OF  WORKING 

tice  of  working  the  steel  on  its  initial  heat,  that  is,  working  it  before  it 
has  cooled  much  below  the  temperature  of  solidification  after  having 
been  cast  subsequent  to  manufacture  in  the  molten  state,  careful  study 
has  developed  the  fact  that  it  matters  little,  so  far  as  the  effect  on  the 
refinement  wrought  by  the  working  is  concerned,  whether  the  ingot  has 
or  has  not  been  allowed  to  become  completely  cold  before  being  brought 
to  the  required  temperature  for  working.  Therefore,  while  the  idea  is 
contrary  to  the  popular  notion,  the  primary  object  in  the  steel  workers  mind 
should  be  the  improvement  in  quality  of  the  material  he  is  working, 
while  the  shaping  of  the  material  may  be  looked  upon  as  a  secondary 
object. 

SECTION    II. 

SUMMARY  OF  THE   HISTORY   AND   PRINCIPLES    OF   WORKING    STEEL. 

The  Three  Methods  for  Mechanically  Working  Steel:  With 
reference  to  the  manner  of  applying  pressure  to  steel  during  mechanical 
working  there  are  three  possible  methods;  namely,  hammering,  pressing 
and  rolling,  all  of  which  are  extensively  used  at  the  present  time.  The 
shaping  of  steel  by  either  of  the  first  two  methods  is  called  forging.  As 
an  introduction  to  the  study  of  the  rolling  of  steel,  a  brief  resume  of  the 
history,  principles,  and  effects  of  each  of  these  methods  will  not  be  out 
of  place  and  may  be  found  quite  interesting. 

Hammer  Forging:  Hammering  was  the  first  method  employed  by 
man  in  shaping  the  metals.  The  first  forging  was  done  by  hand  hammers 
wielded  by  the  workmen.  The  first  power  hammer,  known  by  the  name 
of  tilt  hammer,  was  built  in  England,  and  was  a  crude  affair  com- 
pared with  the  steam  hammers  now  used.  It  consisted  of  a  beam  of  wood 
hinged  at  one  end  and  provided  with  an  iron  hammer  head  at  the  other.  At 
an  intermediate  point,  engaging  cams  on  a  revolving  shaft  alternately 
raised  the  free  end  and  allowed  it  to  fall  on  a  bottom  die  fixed  upon  a  suitable 
foundation.  Thus  the  top  die  could  be  parallel  to  the  bottom  die  in  only 
one  position,  and  the  larger  the  piece  to  be  forged  the  less  power  there 
was  available  to  forge  it.  The  first  steam  hammer  was  built  in  France 
in  1842.  It  consisted  of  a  two  piece  frame  constructed  so  as  to  support, 
directly  over  a  die  or  anvil,  a  steam  cylinder,  to  the  piston  rod  of  which 
was  attached  a  tup,  or  hammer  head.  By  admitting  steam  into  the  cylinder 
below  the  piston,  the  hammer  was  raised  for  a  distance  equal  to  the  stroke 
of  the  cylinder,  and  then  allowed  to  drop  upon  the  anvil  or  bottom  die. 
This  hammer  had  the  advantage  of  always  keeping  the  top  and  bottom 
dies  parallel,  but  was  still  lacking  in  one  important  particular.  Its  power 
being  derived  from  the  inertia  of  the  falling  tup,  the  hammer  had  the  least 
power  when  it  was  most  needed,  that  is,  when  pieces  of  large  diameter  or 
of  great  thickness  were  being  worked.  This  fault  in  the  single  acting 
hammer  was  corrected  by  the  invention  of  the  double  acting  hammer,  in 


EFFECTS  OF  FORGING  317 

which  steam  is  admitted  at  the  top  of  the  piston  and  employed  on  the 
downward  stroke  as  well  as  for  lifting  the  tup.  The  first  double  acting 
hammer  was  built  at  Midvale,  Pa.,  in  1888. 

Principles  and  Effects  of  Hammering:  The  principles  of  the  hammer 
are  that  of  an  instantaneous  application  of  pressure  applied  to  a  relatively 
small  area.  The  strains  set  up  in  the  metal  are  compressive  and  take 
place  in  a  vertical  direction  in  the  region  below  the  area  subjected  to  the 
force  of  the  blow.  The  crowding  of  the  metal  into  one  region,  however, 
causes  a  small  portion  of  the  blow  to  be  transmitted  in  horizontal  directions. 
The  suddenness  of  the  blow  tends  to  localize  the  effect  and  confine  the 
refinement  to  the  exterior.  This  fact  results  in  a  high  degree  of  refinement, 
provided  the  amount  of  reduction  is  great  or  the  section  worked  is  a  thin 
one,  and  is  one  of  the  reasons  why  it  is  possible  to  make  some  hammered 
material  superior  to  rolled  material.  The  resistance  of  the  metal  to 
deformation  under  shock,  combined  with  the  intermittant  action  of  the 
hammer,  makes  shaping  by  hammer  a  slow  process. 

The  Forging  Press:  The  press  is  an  English  invention,  dating  from 
the  year  1861.  It  was  introduced  into  this  country  about  the  year  1887. 
It  consists  essentially  of  a  hydraulic  cylinder  supported  by  one  or  two 
pairs  of  steel  columns  which  are  anchored  to  a  single  base  casting  of  great 
weight  and  strength.  The  ram  of  the  cylinder  points  downward  and  carries 
an  upper  forging  bitt  vertically  opposite  a  similar  lower  and  stationary 
bitt  which  rests  on  the  base  casting  to  which  the  columns  are  attached.  By 
admitting  water  under  pressure  to  the  cylinder  at  its  top  the  upper  pallet 
is  forced  down  upon  the  material  to  be  forged,  which  rests  upon  the  lower 
pallet.  The  pressure  is  applied  slowly  and  is  gradually  increased  to  a 
maximum  which  may  be  maintained  till  the  metal  yields.  By  means  of 
small  auxiliary  cylinders  the  ram  is  lifted  after  each  application  of  pressure. 
The  pressure  exerted  by  the  forging  press  is  very  great.  In  practice  it 
is  found  that  the  lowest  pressure  that  can  be  employed  to  be  effective  at 
a  full  forging  heat  is  about  1.2  tons  per  square  inch,  but  the  pressures 
employed  in  actual  work  will  often  reach  13.26  tons  per  square  inch. 

The  Effect  of  Pressing :  The  press  differs  very  much  from  the  hammer, 
both  in  action  and  the  effects  produced.  Unlike  the  instantaneous  appli- 
cation of  the  pressure  as  in  the  case  of  the  hammer,  the  action  of  the  press 
is  so  slow  that  a  kneading  of  the  metal  takes  place,  and  the  strain,  instead 
of  being  confined  to  the  surface,  penetrates  deep  into  the  material.  An 
illustration  cited  by  Messrs  Harbord  and  Hall  will  serve  to  demonstrate 
the  difference  in  the  effect  produced  by  the  two  methods  of  working.1 

"If  tests  are  taken  from  the  outer  parts  of  a  gun  forging  which  has  the 
center  trepanned  out,  little  difference  is  found  in  the  strength  of  the 
material,  whether  the  forging  was  done  under  the  press  or  under  the 
hammer,  provided  the  latter  was  sufficiently  heavy  for  its  work;  the 

Vol.  II.  Page  855.  Published  by  J.  B. 


JSee  The   Metallurgy   of     Steel. 
Lippincott  Company,  Philadelphia,  Pa., 


318  METHODS  OF  WORKING 

press  showing,  if  anything,  slightly  better  results.  If,  however,  the  test 
pieces  are  taken  from  the  cores  which  have  been  cut  out  of  the  center  of 
the  forgings,  the  difference  in  the  results  is  so  very  marked  as  to  have  in 
duced  all  the  best  makers  of  heavy  steel  forgings  to  install  presses  in- 
place  of,  or  in  addition  to,  their  large  hammers." 

Advantages  of  the  Press:  Aside  from  its  increased  beneficial  effect 
upon  the  material,  the  press  has  many  advantages  over  the  hammer,  some 
of  which  it  may  be  of  interest  to  cite.  The  absence  of  shock  in  the  press 
is  a  decided  advantage  both  in  the  construction  of  the  machine  and  in  the 
working  of  material.  The  cost  of  working  material  under  a  press  is  less 
than  with  the  hammer  because  the  output  is  greater,  the  press  reducing 
faster  than  the  hammer,  fewer  men  and  less  skilled  labor  are  required, 
and  the  fuel  consumption  per  ton  of  output  is  less.  A  much  greater  propor- 
tion of  the  total  work  put  into  a  press  is  transmitted  to  the  metal  than  is 
the  case  with  the  hammer.  Much  of  the  energy  of  the  latter  is  dissipated 
through  being  absorbed  by  the  spring  in  the  anvil  block  and  by  the  earth. 
For  certain  work,  however,  this  impact  gives  the  hammer  two  advantages : 
first,  it  serves  to  remove  scale;  second,  it  enables  the  hammer  to  strike 
forgings  in  molds  with  greater  ease  than  the  press.  The  difficulty  of 
retaining  water  under  the  extremely  high  pressures  required  by  presses 
gives  the  hammer  an  advantage,  but  this  advantage  is  offset  by  its  greater 
liability  to  breakage. 

Rolling:  Of  all  the  known  methods  of  shaping  steel  from  the  cast 
material,  that  of  rolling,  as  introduced  by  Henry  Cort  in  1783,  though 
perhaps  not  producing  the  best  quality  in  certain  classes  of  product,  has 
come  to  be  the  most  extensively  employed.  Though  Cort  is  rightly  credited 
with  being  the  father  of  modern  rolling,  the  use  of  this  principle  in  shaping 
metals  antedates  his  mill  by  many  years.  Thus,  there  are  records  to 
show  that  in  the  year  1553  a  Frenchman  employed  rolls  to  produce  sheets 
of  uniform  thickness  for  the  stamping  of  gold  and  silver  coin.  In  Sweden 
rolls  were  employed  to  produce  certain  steel  sections  prior  to  the  year  1751, 
and  even  at  that  time  the  assertion  was  made  that  as  much  as  twenty 
times  more  bars  could  be  reduced  in  a  given  time  than  could  be  shaped 
under  the  tilt  hammer  of  those  days.  This  fact,  coupled  with  the  great 
efficiency  of  the  rolling  method,  is  responsible  for  the  universal  adoption 
of  rolling  as  the  favorite  method  of  shaping.  The  rapid  growth  in  the 
production  due  to  the  ever  increasing  demand  for  iron  and  steel,  made  it 
imperative  that  the  most  rapid  method  of  shaping  be  employed.  From 
the  days  of  Cort  to  the  present  time,  the  rolling  mill  has  kept^pace  with 
the  growth  in  production  and  has  passed  through  a  surprisingly  rapid 
process  of  development,  not  only  in  size  and  power  but  in  design  and  in 
the  shapes  of  sections  turned  out.  This  development,  together  with  the 
introduction  of  numerous  appliances  for  handling  the  material  mechanically 
during  the  rolling,  has  multiplied  the  capacity  of  the  mills  many  times. 


PRINCIPLES  OF  ROLLING  319 

Some  modern  mills,  like  the  rod  mill,  will  now  turn  out  a  hundred  times 
as  much  tonnage  in  a  given  time  as  a  mill  of  the  same  size  and  working 
on  rods  of  the  same  size  could  have  done  fifty  years  ago. 

Principle  and  Effect  of  Rolling:  The  process  of  shaping  steel  by 
rolling  consists  essentially  of  passing  the  material  between  two  rolls  revolv- 
ing at  the  same  peripheral  speed  and  in  opposite  directions,  i.  e.,  clockwise 
and  counter  clockwise,  and  so  spaced  that  the  distance  between  them  is 
somewhat  less  than  the  height  of  the  sectidn  entering  them.  Under  these 
conditions  the  rolls  grip  the  piece  of  metal  and  deliver  it  reduced  in  section 
and  increased  in  length  in  proportion  to  the  reduction,  except  for  a  slight 
lateral  spreading  which  is  almost  negligible  in  some  sections.  The  extent 
of  the  spread  will  be  found  to  depend  mainly  upon  the  amount  of  reduction 
and  width  of  the  piece.  Thus  in  rolling  plates,  the  total  spread  may  be 
less  than  that  of  the  first  pass  in  the  reduction  of  two-inch  billets, 
especially  if  the  percentage  reduction  in  sectional  area  in  the  latter  is 
great.  The  nature  of  rolling  may  be  best  explained  by  means  of  the  follow- 
ing diagram. 


I ~     —     •"^^••e-- 


Fia.  49.     Diagram  Illustrating  the  Nature  of  Rolling. 

Let  O  A  C  and  (V  A'  C'  be  two  plain  motionless  rolls  which  are  being 
forced  into  the  bar  AA'  E'E  by  means  of  pressures  applied  vertically  from 
F  and  F'.  The  force  exerted  by  the  resistance  of  the  bar  will  act  along 
the  radii  of  the  rolls,  as  OA,  OC,  O'A',  and  O'C'.  The  resultant  of  all 
these  forces  will  be  in  the  vertical  lines  O  B  and  O'B'.  Vertical  compression 
of  the  metal  will,  however,  occur  only  between  the  points  B  and  B'.  At 
all  the  other  points  between  AC  and  A'  C'  the  metal  is  forced  away  from 
the  rolls  and  the  bar  is  elongated.  If  now  the  rolls  are  made  to  revolve, 
the  lower  one  in  a  clockwise  direction  and  the  upper  in  a  counter  clockwise 
direction,  the  piece  is  reduced  in  size  and  elongated  as  shown  by  figure 
A  A'  D'D.  This  turning  of  the  rolls  introduces  a  second  force,  which 
acts  in  the  direction  of  tangents  to  the  arcs  AB  and  A'  B'  and  is  equal  to 
the  force  of  friction  and  therefore  proportional  to  the  pressure  between  the 
rolls  and  the  piece.  The  result  of  this  force  is  to  subject  the  piece  to  a 


320  METHODS  OF  WORKING 


longitudinal  pull  in  the  direction  of  B  to  D,  this  pull  being  at  its  maximum 
at  B  and  at  its  minimum  at  A.  The  compression,  however,  is  at  its 
maximum  at  A  and  its  minimum  at  B.  The  net  result  of  this  double  action 
is  to  cause  the  metal  to  flow  forward  so  that  the  piece,  reduced  in  size, 
is  delivered  at  a  higher  velocity  than  the  peripheral  speed  of  the  rolls, 
the  evidence  for  which  is  found  in  the  fact  that  the  marks  on  the  piece 
caused  by  a  depression  or  elevation  on  the  rolls  is  farther  apart  than  the 
circumference  of  the  rolls.  A  slight  retardation  of  the  forward  speed  of  the 
piece  on  the  entering  side  may  take  place,  but  this  point  has  not  been 
very  well  established  as  a  fact. 

Rolling  Compared  with  Hammering  and  Pressing:  It  is  a  very 
difficult  matter  to  institute  a  fair  comparison  between  the  effects  of  rolling 
with  those  of  hammering  or  pressing.  Each  method  has  a  field  of  its  own 
with  rather  well  defined  boundaries.  Thus,  many  shapes  are  so  intricate  in 
design  that  rolling  them  is  out  of  the  question,  and  so  they  must  be  formed 
under  the  hammer  or  the  press.  A  crank  shaft  and  a  hammer  head  serve 
as  examples  of  these  classes  of  shape,  which  can  be  produced  in  no  other 
way,  unless  by  casting,  when  they  would  then  be  lacking  in  the  strength, 
ductility  and  soundness  imparted  by  working.  That  the  hammer  and  the 
press  are  both  under  better  control  than  rolls  is  evident,  and  being  slower 
and  more  expensive  to  operate  than  rolls,  these  tools  are  used  on  material  the 
cost  of  manufacture  of  which  is  a  secondary  matter.  Hence,  extraordinary 
care  and  attention  is  given  to  all  phases  of  the  working  of  forged  articles. 
Rolls  on  the  other  hand  are  cherished  for  their  speed,  and  tonnage  is  always 
a  factor  in  rolling.  There  is,  however,  a  small  area  in  which  the  field  of 
operation  of  all  three  instrumentalities  overlap,  as  in  the  shaping  of  billets 
or  blooms  from  ingots.  In  working  these  billets  the  different  effects 
produced  by  the  three  methods  become  visible  as  the  piece  is  shaped. 
When  an  ingot  is  hammered,  the  shape  imparted  to  the  section  is  very 
liable  to  look  like  A  in  Fig.  50.  If  the  blows  are  light  and  delivered  at 
high  velocity,  the  upper  surface  only  will  be  elongated  as  shown  at  B  in 
the  figure.  These  facts  show  that  the  impact  is  almost  entirely  absorbed 
by  the  surface  of  the  metal,  and  to  obtain  the  best  effect  from  hammering 
it  is  necessary  to  continue  the  work  until  the  section  has  been  reduced  to 
one  of  relatively  small  size.  The  deeper  penetration  of  the  work  of  the 
press  is  shown  by  the  rounded  corners  of  the  section  represented  by  the 
figure  at  C.  Any  cavity  at  the  center  of  the  piece  is  closed  under  the 
action  of  the  press,  whereas  the  tendency  of  the  hammer  would  be  to  enlarge 
it.  The  effect  of  rolling  is  influenced  very  markedly  by  the  temperature. 
In  the  first  place  the  temperature,  in  order  to  secure  the  greatest  efficiency 
from  the  rolls,  is  likely  to  be  higher  than  that  required  for  either  hammering 
or  pressing.  In  a  piece  uniformly  heated,  the  flow  of  the  metal  is  slightly 
faster  at  the  two  surfaces  than  in  the  center  in  the  smaller  sections,  while 
in  larger  sections  the  flow  at  the  surface  may  be  very  much  greater.  The 
effect  of  the  additional  plasticity  imparted  by  even  a  slight  rise  in  tern- 


COMPARISON  OF  METHODS 


321 


perature  upon  the  flowing  properties  of  the  metal  is  plainly  visible  in  the 
results  obtained  in  rolling  ingots  under  the  two  conditions  as  illustrated 
by  the  figures  at  D  and  E.  The  fishtailing  of  the  piece  represented  at  D 
shows  that  the  flow  of  the  metal  is  faster  at  the  surface  due  to  the  lack 


Hammering 


B 


Heavy  Strokes 


Light  Strokes 


Pressing 


Rolling 


D 


Center  cooler  than  surface  Center  hotter  than  surface 

FIQ.  50.     Diagram  Illustrating  the  Effects  of  Hammering,  Pressing  and  Rolling. 


of  plasticity  at  the  colder  center.  The  reverse  of  these  conditions  is  shown 
at  E  with  the  corresponding  difference  in  effect.  In  this  case  the  effect 
of  the  working  has  penetrated  to  a  much  greater  depth  and  extent  than 
in  the  previous  case.  The  amount  of  draught  and  the  speed  of  rolling  are 
also  important  factors  in  producing  these  effects,  a  more  thorough  dis- 
cussion of  which  will  be  taken  up  later. 

Rolling  and  Pressing  Ingots:  The  notion  most  prevalent  among 
steel  men,  however,  is  that  the  tendency  of  rolling  is  to  produce  a  more 
superficial  effect  than  either  hammering  or  pressing.  That  this  notion  is 
correct  with  respect  to  pressing  is  indicated  by  the  precautions  taken  in 
casting  large  ingots  for  armor  plate  that  is  to  be  rolled.  Figure  51  shows 
the  difference  in  shape  of  ingots  for  the  press  and  for  the  rolls.  The  concave 
and  diamond  shaped  sides  of  the  ingot  for  rolling  are  formed  to  prevent 
the  loss  due  to  fishtailing,  as  already  explained.  Under  uhe  press  the  two 
surfaces  of  a  square  sided  ingot  are  slightly  rounded,  but,  in  rolling,  a 
square  sided  ingot  would  make  a  concave  sided  plate  which  in  many  cases 
progresses  to  such  an  extent  as  to  cause  actual  overlapping.  It  is  admitted 
by  nearly  every  one,  however,  that  with  very  slow  rolling  and  carefully 
regulated  temperature  that  the  quality  of  rolled  material  may  be  made 
the  equal  of  that  reduced  under  the  press. 


For  Pressing  For  Pressing  For  Rolling 

FIG.  51.     Shapes  of  Ingots  for  Pressing  and  Rolling  Armor  Plate. 


322  THE  ROLLING  MILL 


CHAPTER  III. 

ESSENTIALS  OF  ROLLING  MILL  CONSTRUCTION  AND 
OPERATION. 

SECTION  I. 

THE   ROLLS — THEIR  PREPARATION  AND  ARRANGEMENT. 

Parts  and  Equipment  of  the  Simplest  Type  of  Rolling  Mill:  After 
the  rolls,  themselves,  two  in  number  in  the  simpler  types  of  mill,  the  next 
most  essential  part  of  the  mill  are  the  chocks  or  bearings  which  support 
the  ends  of  the  rolls  and  permit  them  to  be  turned  without  displacement. 
The  chocks  in  turn  are  kept  in  place  by  means  of  the  housings,  which 
together  with  the  adjusting  screws  also  furnish  a  means  by  which  the 
distance  between  the  rolls  is  regulated.  These  parts  constitute  a  stand 
of  rolls.  The  housings  are  bolted  to  shoes  which  rest  upon  a  firm  foun- 
dation, to  which  they  are  always  securely  bolted.  Next  in  im- 
portance are  the  parts  which  connect  the  mill  with  the  driving  shaft. 
First,  there  are  the  spindles  that  transmit  the  power  from  the  pinions 
to  the  rolls,  to  both  of  which  they  are  connected  by  means  of  loosely  fitting 
coupling  boxes.  The  pinions,  supported  in  housings  similar  to  the  roll 
housings,  are  gears,  one  of  which  is  driven  through  a  driving  spindle  in  line 
with  one  of  the  rolls.  They  serve  to  impart  opposite  motions  to  the  rolls. 
The  last  part  of  equipment  essential  to  the  mill  is  the  prime  mover,  which 
in  modern  mills  may  be  a  steam  engine  or  an  electric  motor.  As  to  other  equip- 
ment, reheating  furnaces  are  first  in  importance.  Large  mills  must  also  be 
provided  with  roll  tables  for  handling  the  material.  A  discussion  of  the 
driving  apparatus  is  an  engineering  subject  which  lies  beyond  the  intended 
scope*  of  this  book  and  will  receive  no  further  mention  here.  All  the 
remaining  parts,  however,  should  be  studied  somewhat  in  detail. 

The  Rolls  and  Their  Parts:  Of  the  essential  parts  of  the  rolling 
mill  the  rolls  furnish  a  subject  of  great  interest.  There  are  three  parts  to 
a  roll;  namely,  the  body,  which  is  the  part  on  which  the  rolling  is  done; 
the  necks,  or  the  parts  which  rest  in  the  chocks  and  furnish  the  surface 
upon  which  the  pressure  is  applied  for  reducing  the  size  of  the  piece;  and 
the  wobblers,  one  at  the  outer  end  of  either  neck  or  of  both  necks,  which 
are  formed  by  notching  the  prolongation  of  the  neck  of  the  roll.  Over  the 
wobblers  the  coupling  box  for  driving  the  roll  is  fitted.  In  the  case  of 
plain  rolls,  such  as  are  used  for  rolling  plates  and,  in  part,  for  other  flats, 
these  are  the  only  parts  of  the  roll.  In  the  case  of  rolls  for  other  material, 
grooves  are  cut  into  the  surfaces  of  the  rolls  to  form  the  section  required. 


THE  ROLLS 


323 


A  groove  in  one  of  the  rolls  or  a  combination  of  grooves  in  the  two  rolls, 
which  at  the  line  of  contact  forms  an  opening  corresponding  to  the  shape 
of  the  section  desired,  is  called  a  pass.  The  three  most  common  passes 
are  shown  in  the  accompanying  figure. 


I  Open  Box 


Closed  Box 


.ill  Diamond  {90 °)  IV  Gothic 


FIG.  52.  Showing  Different  Types  of  Passes  For  Roughing  and  Semi-finishing  Mills 
I,  III  and  IV  are  spoken  of  as  open  passes  while  II  is  called  a  closed  pass. 
In  the  closed  pass  the  piece  is  buried  in  one  of  the  rolls  so  that  three  sides  are 
enclosed  by  the  groove  A,  the  fourth  side  being  closed  by  the  tongue  or  former 
D,  on  the  other  roll.  Collars  are  represented  at  O  and  Ci.  Passes  I  and  II 
are  commonly  spoken  of  as  box  passes,  while  III  is  called  the  diamond  pass, 
and  IV  the  Gothic  pass. 

The  Manufacture  of  Rolls  is  a  separate  industry,  and  the  art  of  roll- 
making  is  not  widely  known  even  among  the  users  of  rolls.  When  the  work 
the  rolls  have  to  do  is  considered,  together  with  their  effect  upon  the  product 
of  the  mill,  the  importance  of  good  rolls  is  better  appreciated.  Most  rolls 
are  castings,  yet  they  must  be  ductile  to  withstand  the  shock  produced 
as  the  piece  enters  them;  strong  to  resist  sufficiently  the  great  pressure 
applied  to  their  ends;  hard  to  give  them  good  wearing  qualities;  and  sound, 
so  that  they  may  not  develop  surface  defects  which  would  leave  their  marks 
on  every  surface  rolled  on  them  and  cause  the  material  to  be  rejected. 
To  secure  these  qualities  the  best  of  materials  and  the  greatest  of  skill 
are  required  in  their  manufacture.  The  materials  are  of  three  kinds,  namely, 
cast  iron,  steel  and  alloy  mixtures.  From  these  materials  four  kinds  of 
rolls  are  produced.  They  are  known  as  sand  rolls,  which  are  made  of  pig 
iron;  chilled  rolls,  also  of  cast  iron;  steel  rolls,  made  of  steel  by  casting; 
and  "adamite"  rolls,  which  is  a  trade  name  for  a  metal  produced  by  mixing 
steel  with  pig  iron  containing  certain  percentages  of  chromium  and  nickel, 
or  by  mixing  steel  and  the  ferro  alloys  of  these  elements  with  the  proper 
amount  of  an  ordinary  pig  iron  of  high  grade.  As  an  example  of  how  rolls 
are  made,  some  of  the  processes  as  carried  out  by  one  of  the  leading  manu- 
facturers of  rolls  will  be  briefly  described. 

The  Sand  Roll:  Sand  rolls  are  cast  in  a  sand  mold.  The  sand  used 
is  a  loamy  sand  of  a  special  kind  obtained  only  from  deposits  left  in  old 
water  courses.  This  sand  contains  sufficient  clay  intimately  mixed  with 
the  silica  to  form  a  firm  bond  and  yet  be  refractory  enough  that  it  will 
not  fuse  at  the  temperature  of  the  molten  iron.  The  mold  is  prepared  by 
ramming  this  sand,  moistened  a  little,  into  a  half  flask,  and  then  sweeping 


324  THE  ROLLING  MILL 


the  sand  from  the  half  flask  with  a  sweep,  the  outline  of  which  is  similar 
to  the  contour  of  the  roll.  Two  such  half  flasks  are  required  for  each  roll, 
each  one  containing  one-half  of  the  roll  divided  longitudinally.  After 
sweeping  and  smoothing,  the  half  molds  are  coated  inside  with  a  plumbago 
or  other  carbonaceous  dressing  and  carefully  dried.  Just  before  casting, 
these  two  parts  of  the  mould  are  firmly  clamped  together  and  are  set  in 
a  vertical  position  for  pouring,  for  which  purpose  a  casting  pit  is  provided 
for  large  rolls.  Thus,  one  end  of  the  roll  forms  the  bottom  of  the  casting, 
the  other  end  the  top.  The  top  is  capped  by  a  cope  to  provide  a  deep  sink- 
head,  which  is  cut  from  the  roll  after  casting.  The  gating  to  the  mold 
enters  the  flask  at  the  bottom  neck  of  the  roll  and  on  a  tangent,  so  that 
a  swirling  action  is  imparted  to  the  molten  metal  as  it  rises  in  the  mold. 
In  this  way  all  dirt  and  other  foreign  matter  is  forced  to  the  center,  which 
condition  insures  the  outer  portion  of  the  roll  will  be  composed  of  cle*an 
metal. 

The  Materials  Used  in  Sand  Cast  Rolls  are  charcoal  iron  and  roll 
scrap.  The  mixtures  are  melted  in  coal  fired  reverberatory  furnaces. 
The  bath,  sealed  off  from  outside  air,  is  separated  from  the  grate  by  a 
bridge  wall,  over  which  a  non-oxidizing  flame  sweeps  and  furnishes  the  heat 
for  melting.  In  the  melting  a  little  carbon,  silicon,  and  manganese  are 
removed  from  the  metal,  and  by  the  time  the  charge  is  melted  a  highly 
silicous  slag  has  formed,  which  protects  the  metal  from  any  further  action 
that  might  be  produced  by  the  flame.  As  soon  as  the  metal  is  melted, 
fracture  tests  are  taken,  by  means  of  which  the  metallurgist  in  charge 
is  able,  from  long  experience,  to  determine  when  the  bath  is  of  the  right 
composition  to  produce  the  kind  of  roll  desired.  The  molten  metal  is 
tapped  from  the  furnace  into  a  small  tilting  ladle,  which  is  carried  by 
overhead  crane  to  the  molds,  and  the  metal  is  poured  into  the  gate  over  the 
lip  of  the  ladle.  The  pouring  is  very  rapid  and  must  be  continuous,  as  the 
slightest  interruption  would  ruin  the  casting.  After  the  metal  has 
solidified  and  cooled  sufficiently,  the  mold  is  removed,  and  the  roll  is 
cleaned  of  the  adhering  sand,  when  it  is  ready  to  be  machined  to  the  size 
and  shape  required. 

Chilled  Rolls:  Rolls  of  the  chilled  type  are  made  up  of  three  layers 
of  metal,  each  of  which  represents  a  type  of  the  same  original  metal.  The 
interior  of  these  rolls  is  composed  of  grey  iron,  which  is  enclosed  by  a 
cylinder  of  mottled  iron,  and  outside  of  this  a  similar  layer  of  white  iron, 
called  the  chill.  This  composite  structure  is  procured  by  taking  advantage 
of  the  peculiar  properties  exhibited  by  pig  iron  on  cooling  from  the  molten 
state.  In  this  state  iron  holds  in  solution  all  the  carbon  which  it  contains 
at  a  given  temperature.  In  cooling  some  of  this  carbon  separates  in  the 
form  of  crystals  of  graphite,  which  is  distributed  throughout  the  mass; 
the  remainder  is  spoken  of  as  combined  carbon,  the  effect  of  which  is  to 
increase  the  hardness  of  the  metal.  The  separation  of  the  graphite  depends 
mainly  upon  the  rate  of  cooling,  so  that  if  the  iron  is  cooled  very  suddenly 


CHILL  ROLLS 


325 


all  the  carbon  may  be  retained  in  solution  as  combined  carbon,  which 
renders  a  chilled  iron  that  is  dense,  white,  intensely  hard,  and  capable  of 
receiving  a  very  high  polish.  In  making  these  rolls  only  the  body  of  the 
roll  is  given  a  chill.  This  chilling  of  only  a  part  of  the  roll  is  effected  by 
making  that  part  of  the  mold  corresponding  to  the  necks  and  wobblers  of 
sand,  while  that  part  destined  to  form  the  body  is  made  up  of  a  heavy 
cast  iron  ring,  usually  built  up  in  sections  which  are  carefully  turned  at 
the  joints  and  bored  out  true  inside.  After  giving  the  inside  of  the  mold 
a  coating  of  the  carbonaceous  wash,  they  are  warmed  to  remove  moisture, 


The  line  in  the  cut  marks  the  limit  of  clear  chill.    When  depth  of  chill   is 
designated,  it  is  assumed  to  mean  clear  chill. 

FIG.  53.     Method  of  Measuring  Depth  of  Chill  on  Rolls. 


then  assembled,  and  the  casting  is  made  as  for  sand  rolls.  The  rapid 
cooling,  caused  by  the  absorption  of  the  heat  by  the  cold  casting  in  contact 
with  the  molten  metal,  causes  the  chill  on  the  outer  surface  of  the  roll, 
the  depth  and  hardness  of  which  is  controlled  by  varying  the  composition 
of  the  molten  iron.  Chilled  rolls,  once  they  are  formed,  cannot  be  softened 
or  hardened  by  heat  treatment,  as  such  treatment  would  destroy  the  chill 
A  patented  chill  is  now  in  use.  It  is  made  in  the  form  of  a  ring  com- 
posed of  segments  of  solid  metal  on  the  inside  and  a  water  cooled  ring 
on  the  outside.  This  construction  has  the  effect  of  causing  the  mold  to 
become  smaller,  as  it  is  warmed  by  the  heat  from  the  molten  metal,  thus 
subjecting  the  roll  to  a  high  pressure,  which  is  said  to  give  a  more  even 
chill  and  a  denser  and  tougher  material  than  the  common  chill.  The  chill 


326  THE  ROLLING  MILL 


is  measured  by  the  least  depth  of  clear  chill  as  shown  in  the  accompanying 
photograph,  while  the  analysis  of  each  of  the  three  regions  here  depicted 
is  given  in  the  following  table: 

Table  48.    Analysis  of  Different  Parts  of  a  Chilled  Roll. 


TOTAL,    COMB  D.    GRAPH. 
CARB.     CARB.      CARB. 


Chill 3.00        3.00        90        .04        .200        .25 

Mottled 3.00        2.25          .75         .90        .04        .200        .25 

Grey 3.00        1.00        2.00         .90        .04        .200        .25 

Difficulties  in  Making  Chilled  Rolls:  The  greatest  of  skill  and 
experience  are  required  in  the  making  of  chilled  rolls.  The  process  of 
chilling  causes  the  different  parts  of  the  roll  to  cool  at  different  rates  and 
sets  up  stresses  in  the  casting  which  make  it  liable  to  crack  and  break. 
The  range  of  temperature  at  which  the  metal  may  be  poured  is  very  narrow, 
while  a  very  slight  change  in  the  chemical  composition  of  the  metal  will 
sometimes  produce  a  marked  effect  upon  the  chill,  changing  both  the  depth 
and  the  hardness.  The  size  of  the  roll  also  affects  the  nature  and  extent 
of  the  chill.  Besides,  the  roll  in  use  is, subject  to  great  pressure,  uneven 
stresses,  uneven  heating,  over  heating,  and  sudden  cooling,  all  of  which 
tend  to  cause  the  chill  to  crack  and  spall.  This  tendency  to  spall  is  over- 
come by  the  manufacturer  to  some  extent,  but  careful  handling  of  the  roll 
in  use  is  essential  also.  Large  rolls  are  especially  difficult  to  cast  properly. 
The  largest  chilled  rolls  are  made  for  rolling  plates,  and  a  very  tough 
chill  is  required.  The  chills  for  one  of  the  largest  of  these  rolls  weighs 
105,000  pounds  and  the  roll  itself  requires  80,000  pounds  of  metal  to  cast 
it,  while  the  total  length  of  the  mold  is  twenty-three  feet.  A  large 
percentage  of  these  rolls  are  lost  in  casting,  due  to  the  cracking  of  the  roll 
at  places  where  the  different  sections  of  the  chill  are  joined.  Small  chilled 
rolls  are  used  in  guide,  rod,  hoop  and  bar  mills,  and  for  a  variety  of  purposes, 
but  chilled  rolls  for  shapes  are  very  difficult  to  make  owing  to  the  fact  that 
the  collars  in  such  rolls  are  liable  to  bind  in  the  chill  and  crack  off.  All 
these  factors  tend  to  make  chilled  rolls  very  expensive,  but  a  much  greater 
tonnage  is  obtained  from  them  than  from  any  other  kind,  and  their  use  is 
imperative  where  a  very  fine  finish  is  required  to  be  imparted  to  the  product. 

Steel  Rolls  are  cast  in  sand  in  much  the  same  way  as  sand  rolls.  In 
this  case,  however,  ganister  sand  mixed  with  a  little  fire  clay  to  act  as  a 
bond  is  used,  because  the  higher  temperature  of  molten  steel  will  heat 
any  but  the  most  refractory  sands  to  their  fusion  point.  Steel  rolls  are 
stronger  and  more  ductile  than  sand  rolls.  The  deflection  of  a  steel  roll 
under  a  given  load  is  only  about  half  as  much  as  that  of  a  common  sand 
roll.  Besides,  they  may  be  annealed,  when  they  become  almost  unbreak- 
able. They  cannot  be  permanently  hardened,  because  any  hardening  by 
heating  and  quenching  is  removed  by  contact  with  the  hot  metal,  the  heat 
from  which  produces  the  same  effect  as  a  drawback.  On  account  of  their 


ROLL  DESIGNING  327 


unavoidable  softness,  then,  steel  rolls  do  not  wear  well,  and  hence  cannot 
be  used  on  finishing  stands.  For  blooming  mills  and  roughing  stands  of 
other  mills  where  great  strength  is  required,  these  rolls  are  invaluable, 
and  they  are  used  in  such  stands  almost  exclusively.  Occasionally,  where 
a  good  finish  on  the  product  is  not  required,  steel  rolls  will  be  used  on  the 
finishing  stands.  The  material  used  is,  for  the  most  part,  acid  open  hearth 
steels  varying  from  .40%  to  .65%  in  carbon  content.  When  steel  rolls  are 
used  for  finishing,  the  carbon  content  is  increased  to  186%,  and  sometimes 
to  as  high  as  1.25%. 

Other  Rolls :  In  an  attempt  to  overcome  the  defective  softness  of 
steel  rolls  and  at  the  same  time  retain  their  great  strength  and  toughness 
the  alloyed  mixture  previously  referred  to  as  "adamite,"  has  been 
developed.  These  rolls  are  being  used  with  considerable  success,  and  seem 
to  hold  promise  of  even  greater  efficiency.  Forged  steel  rolls  have  also 
been  tried  and  found  to  be  very  satisfactory,  but  their  high  cost  prohibits 
their  use  except  where  exceptional  strength  is  required. 

The  Size  of  Rolls :  In  length  of  body,  rolls  vary  from  one  to  seventeen 
feet,  and  in  diameter  from  seven  to  forty-eight  inches.  The  largest  rolls 
are  used  on  the  plate  mills,  the  smallest  on  the  small  hand  guide  mills. 
On  account  of  the  smaller  surface  exposed  to  pressure,  small  rolls  cut  into 
the  metal  with  greater  ease  than  large  ones  and  so  require  less  power  to 
do  the  same  work.  Therefore,  the  heavier  the  rolls,  the  heavier  must  be 
the  machinery  throughout  the  mill.  The  factor  most  important  in  determin- 
ing the  size  of  the  roll  is  that  of  strength,  and  for  the  sake  of  safety  rolls  as 
large  as  practicable  will  be  employed;  first  cost  is  of  secondary  importance. 
The  resistance  of  a  plain  roll  to  transverse  stress  is  proportional  to  the 
cube  of  its  diameter,  and  inversely  proportional  to  the  length  of  its  body. 
The  diameter  of  the  roll  at  the  base  of  the  deepest  groove  determines  the 
strength  of  a  grooved  roll;  so,  for  grooves  of  the  same  depth,  one  set  of 
rolls  may  be  many  times  stronger  than  another  only  one  or  two  inches 
smaller  in  diameter.  The  size  of  rolls  is  expressed  by  writing  the  diameter 
and  the  length  of  body  in  inches,  with  the  X  sign  between.  Thus  42"  X 
60"  means  that  the  roll  is  forty-two  inches  in  diameter  and  sixty  inches 
long  in  the  body. 

Roll  Design:  Designing  the  rolls  was  originally  one  of  the  duties  of 
the  mill  superintendent,  the  roll  turner  or  the  roller,  but  the  demands 
upon  the  mills  in  the  way  of  new  sections  made  it  necessary  to  place  this 
work  in  the  hands  of  men  specially  trained  to  the  work,  so  that,  now,  roll 
designing  is  a  distinct  profession.  There  are  few  rules  in  the  trade,  and 
the  roll  designer  must  depend  mainly  upon  experience  for  guidance.  It  is 
seldom,  therefore,  that  two  roll  designers  will  be  found  to  develop  a  section 
in  precisely  the  same  way.  That  exceptional*  ingenuity  and  extreme 
resourcefulness  is  required  in  this  profession  is  attested  by  the  wonderfully 
intricate  shapes  these  men  are  turning  out,  and  that,  too,  with  the  most 
astonishing  accuracy. 


328  THE  ROLLING  MILL 


Methods  of  Procedure  in  Designing  Rolls:  Given  a  new  section  to 
evolve,  the  roll  designer  proceeds  in  some  such  manner  as  follows: — From 
a  drawing  of  the  section,  if  he  has  decided  it  is  one  that  can  be  rolled  success- 
fully, he  will  have  a  templet  made  of  the  exact  dimensions  of  the  section, 
and  from  this  templet  another  for  the  finishing  pass  in  which  an  allowance 
of  about  .015  inch  per  inch  of  dimension  of  the  finished  piece  is  made  for 
contraction  of  the  metal  in  cooling  from  the  finishing  temperature  to 
atmospheric  temperature.  He  must  then  decide  on  the  proper  size  of  rolls 
to  use,  which  determines  the  mill  that  is  to  roll  the  section.  This  decision 
made,  he  has  given  the  approximate  size  of  the  billet  or  bloom  from  which 
to  begin,  the  number  of  sets  of  rolls,  and  the  number  of  passes  in  which 
the  work  must  be  done.  Having  given,  now,  the  first  and  last  passes  with 
their  dimensions,  and  the  total  number  of  passes,  he  may  begin  the  design 
of  the  intermediate  passes.  This  he  does  by  drawings  which  are  begun 
by  setting  off  a  "construction  line"  or  '  'pitch  line"  as  it  is  sometimes 
called.  This  line  locates  the  center  of  gravity,  or  the  center  of  figure,  of 
the  various  passes  and  is  usually  placed  midway  between  the  axis  of  rotation 
of  the  two  rolls. 

Difficulties  in  Designing  Rolls:  Having  drawn  the  pitch  line,  the 
roll  designer  then  proceeds  to  mark  off  the  passes  from  billet  to  finishing 
pass,  and  in  doing  so  he  has  a  multitude  of  things  that  must  be  kept  in 
mind,  some  of  which  are:  1.  The  method  of  shaping  is  one  of  squeezing, 
spreading,  and  bending.  2.  The  total  amount  of  reduction  is  best  dis- 
tributed among  the  various  passes  as  evenly  as  possible,  excepting  the 
finishing,  which  is  reserved  to  true  up  the  shape.  3.  All  sides  of  the 
piece  should  be  thoroughly  worked.  4.  The  piece  should  not  enter  two 
successive  passes  in  the  same  position,  as  otherwise  the  metal  will  be 
squeezed  out  between  the  roll  and  form  what  is  known  as  a  fin.  5.  Since 
they  weaken  the  roll  very  much,  deep  cuts  into  a  roll  should  be  avoided. 

6.  The  passes  should  be  so  shaped  as  to  eliminate  side  thrust  on  the  rolls. 

7.  A  piece  will  not  enter  a  pass  in  the  rolls  if  all  its  dimensions  are  larger 
than  the  pass.    8.     The  thin  parts  of  a  section  cool  faster  than  the  heavier 
parts,  and  must,  therefore,  be  formed  in  the  last  passes.    9.     Sections  that 
require  deep  grooves  in  the  rolls  are  difficult  to  roll  successfully  on  account 
of  the  difference  in  the  peripheral  speed  of  the  bottom  and  the  top  of  the 
groove.     The  part  of  the  roll  having  the  greatest  diameter  elongates  the 
piece  more  rapidly  than  the  part  having  the  smallest  diameter  and  tends 
to  cause  the  piece  to  twist  and  curl  on  leaving  the  rolls.     This  difficulty 
can  be  overcome  by  using  rolls  of  slightly  different  diameters,  by  raising 
or  lowering  the  center  of  mass  of  the  piece  from  the  pitch  line  or  by  reduc- 
ing the  amount  of  reduction  on  the  part  that  elongates  the  more  rapidly. 
10.     The  draught  on  the  various  parts  of   a  section  must  be   properly 
proportioned,  as  otherwise  the  piece  will  contain  waves  or  be  distorted  in 
other  ways.     11.     He  must  also  keep  in  mind  that  all  kinds  of  steel  do  not 
work  alike,  and  what  can  be  done  with  open  hearth  steel,   for   instance, 


TURNING  AND  DRESSING  ROLLS  329 

would  be  impossible  with  Bessemer  and  vice  versa.  With  these  difficulties 
to  contend  with,  even  highly  experienced  roll  designers  may  fail  on  the 
first  trial  at  a  new  section.  In  that  case  an  entirely  new  set  of  rolls  may 
be  required,  which  adds  much  to  the  expense  of  rolling  the  section.  Besides 
questions,  such  as  those  above,  that  affect  the  shaping  of  the  material, 
the  roll  designer  is  also  expected  to  consider  time  and  cost.  So,  he  will 
endeavor  to  avoid  roll  changes  or  other  operations  that  will  delay  the  work 
or  add  to  the  cost  of  the  rolling  operation.  Thus,  it  will  be  found  that  in 
most  mills  one  set  of  roughing  rolls  will  be  used  to  produce  a  great  number 
of  different  sections.  This  has  the  effect  of  giving  the  designer  a  fewer 
number  of  passes  with  which  he  forms  the  shape,  and  adds  much  to  the 
difficulty  of  his  task. 

Turning  the  Rolls:  Having  designed  all  the  passes  for  the  rolling  of 
a  given  section,  a  set  of  templets,  one  or  more  for  each  pass,  is  made.  These 
templets  are  to  be  used  in  turning  the  roll,  for  which  purpose  a  special  set 
of  tools  may  be  required.  In  the  roll  shop,  the  rolls  are  first  centered. 
Various  methods  may  be  used  for  finding  the  center.  When  this  point  has 
been  located,  a  lead  hole  may  be  made  with  a  ratchet  drill,  and  then  widened 
out  to  the  proper  angle  with  a  reamer  to  a  depth  of  about  %  inch.  The  roll 
is  then  placed  in  the  necking  lathe,  when,  supported  by  the  center  holes, 
the  necks  may  be  turned  to  exact  size,  or  they  may  be  machined  to  near 
the  exact  size  and  finished  by  grinding  and  polishing.  Since  the  center 
holes  are  liable  to  wear  down  irregularly  if  used  throughout  the  process 
of  turning,  the  body  of  the  roll  is  turned  in  another  lathe  in  which 
the  roll  is  supported  by  chocks  that  fit  the  necks.  Here  the  roll 
is  turned  down  to  size,  and  the  passes  cut  in  to  fit  the  templet  supplied 
by  the  roll  designer.  When  one  roll  is  completed,  it  is  placed  in  chocks 
higher  up  in  the  housing,  and  the  second  roll  is  placed  below  it,  where  it 
may  be  turned  with  the  finished  roll  as  a  guide,  so  that  the  two  parts  of  the 
passes  may  be  made  to  fit  exactly.  With  ordinary  tools,  chilled  rolls  are 
seldom  turned  with  a  surface  speed  of  more  than  fifty-six  inches  per  minute, 
but  with  tools  made  of  high  speed  tool  steel  this  speed  may  be  increased 
to  seventy-two  inches  per  minute.  Speeds  twice  as  great  as  these  may  be 
employed  for  turning  the  other  kinds  of  roll. 

Dressing  the  Rolls:  After  a  set  of  rolls  has  been  in  service  a  variable 
length  of  time,  the  passes  become  worn  to  such  an  extent  that  they  no  longer 
produce  the  section  to  the  required  dimensions,  and  they  must  then  be 
replaced  by  another  set.  In  most  cases  these  worn  out  rolls  may  be  turned 
again,  or  dressed  down,  so  as  to  give  the  correct  size  once  more,  or  if  the 
section  is  of  such  shape  that  this  refitting  is  impossible,  the  passes  may  be 
enlarged  to  produce  a  section  similar  in  shape  to  the  first  one  but  of  greater 
weight.  This  wearing  of  the  rolls  is  one  reason  why  rolling  tolerance  is 
required  on  all  materials. 


330  THE  ROLLING  MILL 


Types  of  Mills:  Before  proceeding  farther  it  may  be  well  to  explain 
that  there  are  two  main  types  of  mill,  referred  to  as  Two=high  and  Three= 
high  mills.  As  the  names  indicate  the  classification  is  based  on  the  manner 
of  arranging  the  rolls  in  the  housings,  a  two-high  stand  consisting  of  two 
rolls,  one  above  the  other,  and  a  three-high  having  three  rolls  thus  arranged. 
In  all  three-high  mills,  each  roll  revolves  continuously  in  one  direction  only, 
whereas  in  two-high  mills  the  direction  of  the  rolling  may  be  in  one  direction 
only,  or  in  opposite  directions  at  different  intervals,  in  which  case  they 
are  called  reversing  mills. 

In  the  old  days  before  the  invention  of  the  three-high  mill  or  the 
reversing  engine,  if  it  was  desired  to  pass  the  bar  more  than  once  through 
the  same  stand  of  rolls,  the  catcher  returned  the  piece  to  the  roller  by 
placing  it  on  the  top  of  the  upper  roll,  which  carried  it  in  the  direction 
opposite  to  that  in  which  it  moved  at  the  bottom  of  the  roll.  Mills  in 
which  this  practice  prevailed  were  called  pull=over  or  drag=over  mills  and 
are  to  be  looked  upon  as  the  fore-runner  of  the  reversing  mill.  In  the  first 
mill  of  the  reversing  type  a  ratchet  gear  furnished  the  means  for  reversing 
the  mill.  Pull-over  mills  are  still  in  use,  and  are  the  mills  most  often 
employed  for  rolling  sheets.  Another  kind  of  two-high  mill  is  the  continuous 
mill,  which  consists  of  several  stands  of  rolls  arranged  in  tandem  and 
propelled  with  a  single  engine.  Guide,  loop  and  the  so  called  Cross 
country  mills  are  made  up  of  several  two-high  stands  and  one  or  more 
three-high  stands.  Guide  mills  are  small  hand  mills  consisting  of  several 
stands  of  rolls  in  a  train.  They  take  their  name  from  their  having  metal 
guides  to  support  the  piece  as  it  enters  the  various  passes.  In  many  guide 
mills  it  is  the  practice  of  the  catchers,  in  order  to  save  time,  to  start  the 
piece  through  each  of  the  passes  before  it  is  through  the  preceding  one, 
thus  forming  a  loop.  After  the  institution  of  this  practice  it  was  found 
that  the  loop  could  be  made  by  means  of  a  tube  or  trough,  called  a 
repeater,  and  thus  dispense  with  the  catchers.  Such  a  contrivance  is  a 
part  of  many  modern  bar  and  strip  mills.  The  cross  country  mill  is  made 
up  of  several  stands  of  rolls,  arranged  in  trains  or  trains  and  tandem  sets. 
The  bar,  propelled  mechanically  by  means  of  live  rolls,  transfers,  etc., 
must  reverse  its  course  two  or  more  times  to  pass  through  the  various  sets 
of  rolls  from  the  furnace  to  cooling  tables.  These  mills  represent  one  of  the 
latest  and  most  efficient  types.  Combination  mills  are  those  in  which  the 
roughing  or  major  part  of  the  reduction  is  done  in  continuous  rolls  and  the 
shaping  in  a  guide  or  loop  mill.  The  Universal  Mill  is  one,  which,  in  addi- 
tion to  the  horizontal  rolls,  usually  arranged  two-high  but  occasionally  three- 
high,  is  provided  with  vertical  rolls,  all  set  in  one  housing.  These  mills  origin- 
ally contained  but  two  vertical  rolls  on  one  side  only  of  the  horizontal  rolls,  but 
in  modern  mills  there  are  two  sets  of  vertical  rolls,  one  set  on  either  side  of  the 
horizontal  ones.  The  mill  is  used  for  rolling  plates  and  eye  bars  that 
require  rolled  edges.  Besides  these  types,  there  are  many  special  mills, 
usually  named  from  the  inventors,  such  as  the  Gray  mill  for  rolling  beams 


THE  CHOCKS  331 


and  H-sections;  the  Wenstrom  mill,  a  kind  of  universal  mill  for  rolling  bars; 
Sack's  mill  for  rolling  shapes,  also  a  development  of  the  Universal  mill;  and 
the  Schoen  mill,  which  rolls  car  wheels.  Opportunity  will  be  given  later  to 
become  better  acquainted  with  most  of  these  mills. 


SECTION   II. 

PARTS   OF  THE   MILL  ESSENTIAL  TO  THE   OPERATION   OF  THE   ROLLS. 

The  Chocks :  As  previously  indicated,  the  chocks  furnish  the  bearings 
in  which  the  necks  of  the  rolls  turn.  They  are  usually  made  in  two  parts. 
The  surface  in  contact  with  the  neck  is  made  of  brass,  bronze,  or  white 
metal,  which  can  be  replaced  as  necessary.  The  use  of  these  alloys  is 
necessary  in  order  to  reduce  friction,  which  is  much  less  between  metals  of 
different  kinds  due  to  difference  in  size  of  the  molecules  or  grains,  and  to  the 
tendency  of  the  softer  metals  to  flow.  The  approximate  composition  of 
some  of  the  more  common  of  these  alloys  is  given  in  the  sub-joined  table 
of  analyses. 

Table  49.     Composition  of  Bearing  Metals. 

NAME  OF  ALLOYS  %  COPPER  %  ZINC  %  TIN  %  ANTIMONY   %  LEAD 

Red  Brass 85  15                                   .' 

Yellow  Brass....  65  35                                   

Bronze,  No.  1 ...  85  . .  15              

Bronze,  No.  2. ..  82  15  3              

White  Metals ....  0  to  6  10  to  15  12  to  20        65  to  80 

Since  1915,  a  new  white  metal  composed  of  lead,  about  98.5%,  and 
sodium,  about  1.5%,  has  been  used  with  much  success.  As  all  these  metals 
are  soft  and  not  very  strong,  it  is  necessary  to  carry  them  in  castings,  which 
are  set  into  the  housings.  These  castings  are  box-like  in  shape,  each  one 
containing  on  one  side  a  semi-circular  groove  corresponding  to,  but  larger 
than,  the  necks  of  the  rolls.  In  order  to  reduce  their  weight,  they  are  cored 
out,  and  may  be  made  of  either  iron  or  steel. 

The  Arrangement  of  the  Chocks  in  two-high  mills  is  a  simple  matter. 
Two  chocks  under  the  necks  of  the  bottom  roll,  and  two  similarly  placed 
above  the  top  roll  furnish  the  main  bearings.  In  case  the  top  roll  is 
adjustable,  light  bearings  must  also  be  placed  under  its  necks  to  make  it 
possible  to  support  this  roll.  In  the  heavy  mills  hydraulic  jacks  or  balance 
weights,  placed  under  the  mill,  are  connected  by  vertical  rods  to  the  lower 
chocks  and  serve  to  lift  the  roll  as  desired;  in  the  small  mills,  screw 
bolts  extending  through  the  housing  serve  the  same  purpose.  The  exposed 
half  of  the  neck  of  the  lower  roll  will  usually  be  covered  to  protect  it  from 
scale,  etc.  The  arrangement  of  the  chocks  in  three-high  mills  is  more 


332  THE  ROLLING  MILL 


difficult.  The  simplest  way  is  to  place  double  groove  chocks  between  the 
top  and  middle  and  the  middle  and  bottom  rolls,  and  then  set  them  in  the 
housings  one  above  the  other,  so  that  all  the  adjusting  made  necessary  by  the 
wearing  away  of  the  brasses  and  the  material  of  the  rolls,  themselves,  may 
be  made  with  the  large  set  screws  in  the  top  of  the  housing.  But  this 
arrangement  causes  the  bottom  bearing  to  wear  down  rapidly  and  increases 
the  power  required  to  drive  the  mill,  due  to  the  additional  friction  induced 
on  this  bearing  by  the  weight  of  the  two  upper  rolls  and  their  chocks. 
This  fault  may  be  overcome  in  two  ways:  (1)  By  making  the  bottom 
roll  fixed  and  supporting  this  extra  weight  on  the  shoulders  of  the  chocks 
themselves,  the  distance  between  rolls  may  then  be  regulated  with  shims,  or 
"liners,"  by  adding  or  removing  the  shims  as  the  bearings  wear  down. 
(2)  A  better  way,  and  the  one  most  often  employed  in  modern  mills,  is 
to  make  the  middle  roll  fixed,  in  which  case  the  bottom  roll  is  raised  and 
lowered  by  means  of  an  adjusting  wedge  attached  to  a  screw  in  the 
housing  which  permits  it  to  be  moved  back  and  forth  with  a  wrench  from 
the  outside  of  the  housing.  Other  methods  of  adjusting  this  roll  are  in 
use  also.  A  method  of  supporting  each  roll  separately  by  means  of  hooked 
screws  and  cross  bars  has  also  been  developed,  the  details  of  which  would 
be  unprofitable  to  study  here.  In  all  mills,  two-high  as  well  as  three-high, 
the  top  chocks  are  held  down  by  means  of  two  strong  screws  which  work  in 
threaded  holes  or  nuts  in  the  tops  of  the  housings. 

The  Function  of  the  Chocks  is  not  only  to  furnish  bearings  for  the 
rolls  vertically  but  to  prevent  their  movement  laterally  as  well.  This 
lateral  displacement  of  the  roll  is  prevented  by  the  inner  edge  of  the  bearing 
which  is  formed  to  fit  against  the  shoulder  of  the  roll.  Adjustments  for 
wear  in  this  direction  are  provided  for  by  adjusting  screws  which  extend 
through  the  side  of  the  housing  and  bear  on  the  ends  of  the  chocks.  This 
lateral  adjustment  is  a  matter  of  great  importance  in  rolling  sections  that 
require  grooved  rolls,  the  reason  for  which  is  self  evident. 

The  Housings:  There  are  two  housings  for  each  stand  of  rolls,  they 
may  be  made  of  either  iron  or  steel,  the  choice  of  materials  depending 
upon  the  size  of  the  mill,  the  strength  required,  and  the  preference  of  the 
management.  They  are  castings  of  an  O-orU-form,  each  enclosing  a  space, 
called  the  window,  which  serves  as  a  receptacle  for  the  chocks.  Housings 
may  be  either  closed  topped  or  open  topped;  in  the  former,  the  base, 
the  two  legs,  and  the  top  are  all  cast  in  one  piece,  while  in  the  latter  the 
top  may  form  a  separate  part  which  can  be  removed.  The  base  of  the 
housing  is  cast  with  a  projection  on  each  side,  the  two  forming  the  feet 
of  the  housing.  In  the  bottom  of  each  foot  is  cut  a  groove  which  fits  over 
a  girder,  called  a  shoe,  running  parallel  to  the  rolls.  Suitably  shaped 
bolts  then  serve  to  clamp  the  foot  of  the  housing  to  the  shoe,  which  is 
firmly  fastened  to  the  foundation  by  means  of  long  bolts.  This  method 
permits  the  housing  to  be  moved  laterally,  and  much  facilitates  the  plumb- 


HOUSINGS  AND  PINIONS  333 

ing  and  lining  up  of  the  mill.  The  tops  of  the  two  housings  in  a  set  are 
prevented  from  spreading  apart  by  means  of  suitable  tie  rods,  or  the  tops 
of  both  housings  may  be  cast  in  one  piece.  Similarly,  tie  rods  will  usually 
be  placed  at  the  bottom.  Recesses  or  other  openings  are  cast  in  the 
inside  of  each  housing  to  receive  the  supports  for  the  guards  and  guides/ 
these  supports  being  usually  in  the  form  of  square  bars  which  extend  from 
housing  to  housing  in  front  of  the  rolls.  The  immense  pressure  applied  to 
the  rolls  between  the  top  and  bottom  of  the  housing  acts  as  a  stretching 
force  on  the  uprights  of  the  housings,  and  is  an  important  factor  in  deter- 
mining the  reduction  that  can  be  effected  in  one  pass  and  also  the  exactness 
with  which  the  thickness  of  the  piece  is  controlled. 

The  Adjusting  Equipment  for  the  rolls  has  already  been  located  and 
partly  described  in  the  preceding  paragraphs.  In  addition  it  should  be 
pointed  out  that  in  large  mills,  in  which  the  top  roll  is  adjusted  during  the 
rolling,  power  must  be  supplied  to  operate  the  screws.  To  provide  for  the 
transmission  of  the  power,  the  top  part  of  each  screw,  which  is  made  square 
or  hexagonal  for  a  distance  slightly  greater  than  the  rise  of  the  roll,  passes 
through  the  core  of  a  pinion.  These  pinions  may  then  be  turned  directly  or 
indirectly  with  a  horizontal  hydraulic  cylinder  located  at  a  proper  height, 
usually  on  top  of  the  housings  of  the  driving  pinions;  or,  by  means  of  a 
worm  shaft  and  the  proper  worm  gears,  the  screw  down  may  be  effected 
with  a  small  electric  motor.  In  small  mills  where  the  adjustment  is  only 
occasional,  the  screws  will  be  operated  by  hand  by  means  of  spanner 
bars.  In  all  cases  the  compression  of  these  screws  is  unavoidable  and 
combined  with  the  stretch  of  the  housings  produces  the  spring  of  the  mill, 
which  in  some  cases  is  surprisingly  great. 

The  Pinions:  An  important  part  of  the  mill  is  the  pinions.  They 
arc  broad  faced  steel  gears  located  between  the  prime  mover  and  the  rolls. 
Their  functions  are  to  divide  the  power,  which  is  delivered  by  the  engine 
or  motor  through  a  single  shaft  or  driving  spindle,  usually  spoken  of  as  the 
leading  spindle,  among  the  rolls  and  to  control  their  direction  of  rotation. 
They  run  in  bearings  contained  in  a  pair  of  housings  similar  to  those  for  the 
rolls,  and  should  be  completely  and  tightly  covered  to  protect  them  from 
dust  and  dirt  which  would  cause  them  to  wear  out  rapidly.  They  need 
to  be  well  lubricated,  and  the  present  practice  of  giving  them  an  occasional 
dressing  of  pine  tar,  plumbago,  and  tallow,  or  other  mixture  of  grease,  is 
giving  way  to  the  better  plan  of  having  the  housings  cast  in  one  piece  so 
as  to  form  an  oil  bath  at  the  bottom  in  which  the  bottom  pinion  is  partly 
submerged.  Pinions  are  of  three  kinds,  based  on  the  arrangement  of  the 
teeth.  In  the  oldest  form  the  teeth  ran  straight  across  the  face,  but 
eventually  it  was  found  that  a  smoother  running  pinion  results  if  the  face 
be  divided  into  two  parts  and  the  teeth  of  the  two  halves  staggered,  i.  e., 
set  in  so  that  the  teeth  in  one  half  are  in  line  with  the  space  in  the  other. 
This  design  gives  an  effect  like  that  which  would  be  obtained  if  the  pitch 


334  THE  ROLLING  MILL 


were  decreased.  This  scheme  was  also  found  to  effect  a  saving  in  power. 
Still  another  improvement  results  from  the  use  of  pinions  with  helical  or 
"herring  bone"  teeth,  which  also  tend  to  eliminate  vibration  in  the  pinions, 
as  some  parts  of  the  teeth  are  always  in  contact,  thus  making  the  trans- 
mission of  the  power  continuous.  This  presence  of  jar  when  each  tooth 
comes  into  action  has  an  effect  on  the  material,  as  in  certain  classes  of 
material  the  old  form  of  pinion  was  found  to  produce  marks  on  the  bar  by 
the  jarring  of  the  teeth  meshing  being  transmitted  to  the  rolls.  In  all 
mills  except  plate  mills,  the  distance  from  center  to  center  of  the  pinions 
determines  the  size  of  the  mill. 

The  Connections:  Each  roll,  except  in  the  case  of  friction  driven 
rolls,  is  connected  to  its  pinion  by  means  of  spindles.  They  are  usually 
made  of  cast  steel  and  are  fitted  at  each  end  with  wobblers  like  those  on 
the  rolls.  The  connections  between  pinions  and  spindles  and  rolls  and 
spindles  are  made  with  coupling  boxes.  The  coupling  box  is  a  hollow 
cylindrical  casting,  the  space  in  which  corresponds  in  section  to  that  of  the 
wobbler,  one  end  of  the  box  fitting  over  the  wobbler  on  the  roll  and  the 
other  over  that  of  the  spindle.  In  order  to  safe-guard  the  mill,  the  coupling 
boxes  are  usually  made  the  weakest  part  of  the  mill.  In  some  mills  this 
weak  spot  is  the  leading  spindle,  which  connects  the  pinions  with  the  engine 
or  motor,  instead  of  one  of  the  coupling  boxes.  Since  the  spindle  must  be 
put  in  place  with  the  two  coupling  boxes  on  it,  the  length  of  the  spindle 
must  be  a  little  more  than  twice  the  length  of  the  box.  In  mills,  the  top 
roll  of  which  moves  up  and  down  through  a  great  distance,  the  upper 
spindle  is  thrown  out  of  line  horizontally.  As  it  is  very  difficult  to 
operate  with  a  spindle  more  than  15°  out  of  level,  this  angle  must  be  kept 
within  the  allowable  limit  by  increasing  the  length  of  the  spindle.  In 
such  cases  the  ends  of  the  wobblers  are  cut  from  a  section  of  a  sphere  to 
give  them  the  rounded  form  necessary  to  permit  them  to  work  at  different 
angles,  and  the  spindle  is  supported  by  means  of  saddles  which  rise  and 
fall  with  the  roll  and  hold  the  spindle  in  place. 

Guides  and  Guards:  In  order  to  prevent  collaring  and  to  insure 
that  the  piece  enters  and  leaves  its  pass  in  the  correct  position,  guides 
are  employed.  These  guides  vary  in  form  and  size  to  fit  the  conditions. 
In  some  cases  they  are  merely  grooved  fore-plates;  in  others  they  are  blunt 
edged  plates  set  up  in  front  of  the  collars,  dividing  the  space  in  front  of  the 
rolls  into  a  series  of  pigeon  holes;  in  large  mills  rolling  heavy  sections, 
they  may  take  the  form  of  grooved  rollers;  in  the  smaller  mills  like  the 
guide  mills,  they  are  trumpet  shaped  castings  that  fit  close  up  to  the  roll 
and  have  exit  openings  to  conform  to  the  shape  and  size  of  the  section 
of  the  entering  piece;  in  other  mills,  like  the  continuous  mill,  they  may 
be  so  constructed  as  to  twist  and  thus  turn  the  piece  between  two  successive 
passes.  Guides  may  be  employed  on  both  sides  of  a  pass,  in  which  case 
they  are  designated  as  entering  guides  and  delivery  guides.  They  are  held 


ROLL  TABLES,  ETC.  335 

in  place  by  means  of  the  rest  bars  previously  mentioned  in  connection  with 
the  housings.  Guards  are  devices  employed  mainly  on  the  delivery  side  of 
the  mill  to  control  the  direction  of  the  piece  after  leaving  the  pass.  Reversing 
and  three-high  mills  will  be  provided  with  guards  on  both  sides  of  the  mill. 

Additional  Equipment:  In  addition  to  the  parts  of  the  mill  already 
described,  every  mill  must  be  provided  with  suitable  appliances  for  heating 
and  handling  the  materials  and  disposing  of  the  product.  The  various 
furnaces  for  the  heating  of  the  raw  materials  will  be  described  later.  As 
to  the  handling  of  materials,  it  is  evident  that  reliance  on  man  power  places 
such  restrictions  upon  the  size  and  output  of  the  mill  that,  in  the  case  of 
certain  small  mills  and  of  all  the  larger  mills,  the  appliances  for  handling 
the  materials  mechanically  are  to  be  considered  as  essential  parts  of  the 
mill.  The  number  of  these  appliances  is  so  great  and  the  kinds  are  so 
varied  that  a  detailed  description  of  all  of  them  is  impossible,  and  since 
it  would  be  unprofitable  to  describe  only  a  few  forms,  little  more  than  an 
attempt  to  mention  some  of  the  more  important  ones  will  be  made  here. 
For  getting  heavy  material  in  and  out  of  furnaces  and  delivering  it  to  the 
mill,  electrically  operated  charging  and  drawing  machines  are  used.  These 
machines  are  of  two  general  types,  namely,  those  that  travel  on  overhead 
tracks  and  those  that  move  on  a  track  laid  on  the  mill  floor.  For  handling 
material  during  the  rolling  process,  roll  tables  are  provided  for  large  mills, 
while  various  forms  of  appliances,  called  repeaters,  are  used  on  small  mills. 
Roll  tables  consist  of  a  frame  work  and  a  number  of  rolls,  which  may  be 
rotated  at  will,  mounted  thereon.  For  operating  these  rolls,  the  steam 
engine  has  been  replaced  by  the  electric  motor  in  all  new  mills  and  also 
in  most  of  the  old  ones.  Roll  tables  may  be  either  stationary  or  movable. 
Movable  tables,  often  used  on  three-high  mills,  may  be  of  the  tilting,  the 
lifting,  or  the  traveling  type.  Tilting  tables  are  mounted  on  an  axis  of 
rotation,  which  may  permit  one  or  both  ends,  depending  on  the  location 
of  the  axis,  to  be  raised  and  lowered,  whereas  lifting  tables  always  remain 
in  horizontal  positions  and  may  be  moved  in  up-and-down  directions  only. 
Traveling  tables,  which  are  now  to  be  found  only  on  the  old  mills,  move 
along  on  tracks  laid  on  either  side  of  a  roll  train,  and  may  be  of  the  tilting 
type  also.  After  the  rolling,  cooling  beds,  of  which  there  are  many  types 
and  forms  in  use,  must  be  provided  to  receive  the  material  from  the  mill. 
The  straightening  of  the  material,  which  irregularities  of  the  rolling  and 
cooling  often  makes  necessary,  is  done  in  roll,  or  machine,  straighteners 
or  by  means  of  gag  presses.  In  order  to  keep  up  with  the  mill  only  the  most 
rapid  methods  of  cutting  are  permissible.  For  this  purpose  only  two 
instrumentalities  are  available,  namely,  the  saw  and  the  shear,  either  of 
which  may  be  used  on  hot  or  cold  material.  Shears  are  of  three  general 
types;  namely,  the  alligator,  used  only  for  cutting  light  weight  material; 
the  guillotine,  which  is  employed  generally  for  all  classes  of  work;  and  the 
flying  shear,  designed  to  cut  billets  or  bars  while  they  arc  in  motion.  The 


THE  ROLLING  MILL 


power  employed  to  operate  the  shears  is  hydraulic  for  the  heavier  materials, 
such  as  slabs  and  large  blooms,  while  steam  and  electric  power  are  used 
for  all  other  work. 


SECTION  III.         v 

SOME    GENERAL    FEATURES    PERTAINING    TO    OPERATION    OF    THE    ROLLING    MILL. 

The  Mill  Force:  Of  equal  importance  with  the  equipment  of  a  mill, 
are  the  men  who  operate  it  and  the  organization  and  system  back  of  them. 
Under  the  general  superintendent  of  the  steel  plant  there  may  be  a  number 
of  rolling  mill  superintendents,  each  of  whom  will  have  charge  of  a  group 
of  mills  turning  out  similar  products.  As  his  assistants,  the  mill  superin- 
tendent selects  foremen,  each  of  whom  are  responsible  for  the  successful 
operation  of  one  or  two  of  the  mills.  Below  the  foreman  the  mill  is  divided 
into  departments,  with  a  man  at  the  head  of  each,  who  is  charged  with 
the  performance  of  a  certain  part  of  the  work.  Thus,  there  is  the  heater 
who  has  the  heating  of  the  material  to  look  after;  the  roller,  who  superin- 
tends the  actual  rolling  process;  the  engineer  who  tends  the  engine,  or  an 
electrician,  if  motors  are  used  for  running  the  mill;  and  the  shearmen, 
whose  duty  is  to  see  that  the  product  is  properly  cut.  Besides  these,  other 
departments,  such  as  the  machine  and  the  electric  shop,  the  inspection  and 
shipping  departments,  play  important  parts  in  the  mill  operation,  though 
they  do  not  come  under  the  direct  authority  of  the  mill  superintendent. 
When  it  is  remembered  that  the  failure  of  any  one  of  these  may  close  down 
the  whole  mill,  the  importance  of  system  and  of  the  personnel  of  the  organi- 
zation is  more  fully  appreciated. 

Duties  of  the  Roller:  So  far  as  the  product  of  a  given  mill  is  con- 
cerned, it  would  appear  that  the  roller  and  roll  designer  are  the  chief  figures. 
Co-operation  between  these  two  men  is  essential,  for  in  a  measure  their 
interests  are  identical;  the  roll  designer  decides  how  the  work  is  to  be 
done,  and  the  roller  sees  that  it  is  done  properly.  The  latter  will,  therefore, 
concentrate  his  attention  upon  the  product,  and  with  caliper,  gauge,  or 
templet  will  take  frequent  measurements  to  make  certain  the  material  is 
being  rolled  true  to  the  dimensions  specified.  He  will  keep  a  sharp  look-out 
for  underfills,  overfills,  fins,  guide  marks,  collar  marks,  laps  and  any  other 
rolling  defects,  and  make  the  necessary  adjustments  to  correct  them. 

Fins:  It  is  the  intention  to  discuss  the  defects  of  materials  in  con- 
nection with  the  rolling  of  each  particular  class  of  product,  but  in  all  rolling 
where  grooved  rolls  are  used,  the  occurrence  of  fins  is  so  liable  to  happen 
that  it  is  well  to  consider  them  here,  more  especially  since  there  will  be 
occasion  to  use  the  term  frequently.  Fins  are  formed  when  the  section  is 
too  large  for  the  pass  it  is  entering,  or  whenever,  in  designing  the  pass, 
proper  allowance  has  not  been  made  for  the  spread  of  the  material,  thus 


OPERATING  FEATURES  337 

causing  the  metal  to  flow  out  between  the  flat  bodies  of  the  rolls  on  each 
side  of  the  groove.  If  this  fin  is  thin  and  wide  it  will  be  folded  over  without 
welding  and  form  a  lap,  when  the  piece,  after  turning,  has  been  sent  through 
the  next  pass.  Besides,  fins  may  be  dangerous,  for  if  the  rolls  are  very 
close  together  any  spreading  of  material  between  them  is  likely  to  break 
them. 

The  Different  Passes  and  Stands  in  mills  that  roll  finished  shapes 
are  given  class  names.  Thus  the  first  rolls  the  piece  enters  in  the  mill  are 
used  mainly  to  reduce  the  size  of  the  bloom  or  billet,  and  the  piece  generally 
leaves  them  in  the  same  shape  it  entered.  These  passes  are  called  the 
roughing  rolls  and  the  stand  or  stands  is  spoken  of  as  the  rougher,  or 
roughers.  If  the  succeeding  stand  merely  carries  this  reduction  further, 
it  is  called  the  pony  rougher.  The  stands  and  passes  in  which  the  actual 
shaping  of  the  piece  is  done  are  called  the  strands,  usually  numbered  1,  2, 
etc.  The  pass  next  to  the  last  is  called  the  planisher,  but  since  in  roll 
designing  this  pass  may  be  looked  upon  as  the  first  pass  leading  back  from 
the  finished  section  to  the  bloom,  some  designers  call  this  pass  the  leader. 
The  last  pass  is  always  called  the  finishing. 

Factors  Affecting  the  Rolling  Operation:  In  the  rolling  of  steel 
there  are  five  factors  to  be  considered,  namely,  the  temperature  of  the 
steel  during  the  rolling,  the  chemical  composition  of  the  metal,  the  speed 
at  which  the  rolls  are  revolved,  the  draught  in  each  pass,  and  the  diameter 
of  the  rolls.  Furthermore,  these  factors  should  be  considered  from  the 
three  different  standpoints  of  power,  or  energy,  required  to  deform  the 
steel;  their  effect  upon  the  rolling  properties  of  the  metal,  that  is,  the  way 
it  will  spread,  bend  and  flow  in  the  rolls;  and  their  effect  on  the  quality  of 
the  finished  product.  All  these  matters  have  not  been  fully  investigated, 
and  our  knowledge  concerning  them  is  somewhat  meager,  but  in  order  to 
invite  attention  to  these  subjects,  a  brief  summary  of  what  is  known  about 
these  factors  is  appended. 

Effects  of  Temperature:  The  influence  which  the  working  of  steel  at 
different  temperatures  may  have  upon  the  quality  and  properties  of  the 
product  has  already  been  discussed  under  the  caption  of  Hot  and  Cold 
Working,  (Chap.  II,  Sect.  1.).  Relative  to  the  power  or  energy  require- 
ments and  the  rolling  properties  of  the  metal,  it  is  to  be  observed  that  the 
higher  the  temperature  is  raised  the  more  plastic  the  steel  becomes.  Thus, 
while,  a  .10  per  cent,  carbon  steel,  for  example,  will  give  a  tensile  strength 
of  about  50000  pounds  at  atmospheric  temperatures,  at  600°C  it  will  break 
under  a  pull  of  20000  to  25000  pounds  per  square  inch, .  at  700  °C  under  a  pull 
of  about  11000  pounds,  and  at  800 °C  under  a  pull  of  about  6000  pounds. 
Between  800  °C  and  900  °C  a  distinct  discontinuity  in  the  tensile  strength 
occurs,  with  the  result  that  at  900 °C  the  tensile  strength  will  suddenly 
increase  to  nearly  9000  pounds.  From  this  point  the  strength  decreases 


338  THE  ROLLING  MILL 


with  rising  temperature,  being  about  6500  pounds  at  1000°C.,  about  4600 
pounds  at  1100°C.,  about  3000  at  1200°C.,  and  approaching  zero  at  1460°C., 
the  fusion  point.  From  these  facts  it  would  appear  that  the  higher  the 
temperature  of  the  steel  the  easier  will  it  be  deformed.  But  there  are  other 
features  that  tend  to  keep  both  the  initial  and  final  working  temperatures 
within  certain  well  defined  limits.  Since  steel  assumes  a  semi-fluid  state 
at  temperatures  somewhat  below  its  fusion  point,  heating  to  within 
less  than  200  °C  of  this  point  exposes  it  to  the  danger  of  overheating  or 
so-called  "burning".  For  dead  soft  steels  the  initial  temperature  should 
not  exceed  1250°C,  and  for  high  carbon  steels,  (1.00%  to  1.20%  carbon) 
this  temperature  should  not  exceed  1050 °C.  In  order  to  secure  the  greatest 
refinement  of  grain,  either  the  initial  temperature  or  the  speed  of  rolling 
should  be  adjusted  so  that  the  finishing  temperature  of  the  rolling  will  be 
above,  but  as  near  the  critical  range  of  the  steel  as  possible. 

The  Effect  of  Chemical  Composition  need  be  considered  here  only 
from  the  standpoint  of  energy  required  and  rolling  properties.  As  to  the 
energy  required,  experiments  have  shown  that  slightly  more  work  is 
required  to  roll  a  steel  containing  1.00%  carbon  than  for  steels  containing 
only  .10%  carbon.  Whether  this  difference  was  due  entirely  to  the  lower 
temperature  at  which  the  higher  carbon  steel  was  rolled  or  also  partly  to 
the  higher  content  of  carbon  could  not  be  determined.  In  the  hope  that 
it  would  help  to  solve  this  question,  an  experiment  was  performed  with 
the  object  of  comparing  the  tensile  strength  of  high  carbon  and  low  carbon 
steels  at  rolling  temperatures.  For  this  purpose  three  steels  having  a 
carbon  content  of  .10  percent,  .22  per  cent,  and  1.10  per  cent,  but  otherwise 
of  approximately  the  same  composition,  were  selected.  The  results  from 
pulling  the  first  have  already  been  given.  The  mechanical  properties  of 
the  other  two  were  compared  at  900  °C  only.  The  average  results  obtained 
from  pulling  ten  pieces  of  each  under  similar  conditions  at  the  initial 
temperature  of  900 °C  are  as  follows: 


Elongation    Reduction 

Carbon  Content 

Tensile  Strength 

in  8*             of  Area 

.22% 

13,500  Ibs. 

110%               94% 

1.10% 

18,800  Jbs. 

58%                83% 

These  results  would  indicate  that  the  higher  carbon  steel  is  somewhat  less 
plastic  at  rolling  temperatures  than  the  lower  carbon  steel.  Therefore,  it 
would  require  more  energy  for  rolling,  and  would  not  spread  or  elongate 
as  readily  as  the  steel  of  lower  carbon  content.  As  to  the  effect  of  the 
other  elements  in  plain  steel,  phosphorus  may  produce  effects  similar  to 
those  of  carbon,  sulphur  tends  to  produce  red  shortness,  while  manganese 
tends  to  offset  the  effects  of  sulphur  and  oxygen  and  improve  the  rolling 
properties.  '  Open  hearth  steel,  which  is  low  in  its  phosphorus  content, 
tends  to  spread  more  in  the  rolls  than  does  Bessemer  steel,  which  is  higher 
in  phosphorus.  The  rolling  properties  are  still  more  strongly  affected  by 


OPERATING  FEATURES  339 

certain  alloying  elements,  such  as  nickel  and  chromium.  The  difference  in 
rolling  properties  produced  by  difference  in  chemical  composition  may  not 
be  noticable  in  the  rolling  of  the  simpler  sections,  but  may  cause  much 
trouble  in  the  rolling  of  complicated  sections  with  wide  thin  flanges  or  legs. 
Thus,  in  one  instance  of  such  a  complicated  section,  it  was  found  that  while 
the  section  rolled  perfectly  with  one  heat  of  steel,  it  was  imperfectly  formed 
when  rolled  from  another  heat  in  which  the  carbon  content  was  ten  points, 
the  manganese  fifteen  points,  and  the  sulphur  two  points  higher. 

The  Effect  of  Speed :  The  speed  of  rolling  is  the  factor  which  has  received 
the  least  attention  from  the  viewpoint  of  its  effect  upon  the  material.  It  is 
the  consensus  of  opinion  among  steel  workers,  however,  that  the  speed  of 
rolling  undoubtedly  has  an  influence  upon  the  quality  of  the  product.  It  is 
evident  that  the  faster  a  piece  of  steel  is  deformed  the  less  time  the 
molecules  have  in  which  to  adapt  themselves  to  the  deformation  and  the 
greater  their  resistance  to  the  deformation.  Consequently  the  stretching 
effect  of  the  rolling,  as  previously  explained,  increases  in  undue  proportion 
to  the  compression.  If  the  speed  of  the  rolls  were  increased  sufficiently 
they  would  then  have  a  greater  tendency  to  slip  on  the  piece,  and  the 
stretching  effect  would  tend  to  become  a  tearing  effect.  However,  it  is 
not  speed  alone  that  produces  this  effect  but  draught  and  speed  together. 

Draught:  Draught  is  the  difference  in  sectional  area  between  one 
pass  and  the  next  succeeding  one,  and  is  usually  expressed  in  per  cent. 
While  there  are  cases  where  as  high  as  a  50%  reduction  occurs,  and  one 
case  in  which  a  70%  reduction  is  made  in  a  single  pass,  the  draught  will 
seldom  exceed  36%.  These  heavy  draughts  take  place  in  the  roughers, 
where  most  of  the  reduction  occurs.  In  the  strands  the  reduction  will  be 
as  evenly  distributed  as  possible,  and  will  sometimes  be  as  low  as  10%. 
If  the  leader  is  used  as  a  planishing  pass  very  little  reduction  is  effected 
there  either,  while  very  little  reduction,  with  a  few  exceptions,  ever  occurs 
in  the  finishing  pass.  This  pass  being  intended  to  give  an  exact  finish  to 
gauge  and  to  true  up  the  piece,  it  is  important  that  very  little  work  be  done 
in  it  in  order  that  it  may  be  subjected  to  as  little  wear  as  possible.  Since* 
a  piece  must  be  finished  before  it  has  lost  its  heat  and  has  cooled  below  the 
rolling  temperature,  which  cooling  is  very  rapid  in  the  case  of  small  sections, 
the  rolls  must  be  run  at  a  speed  that  will  carry  the  piece  through  the  rolling 
before  it  has  become  too  cold.  The  number  of  passes  and  the  size  of  the 
piece  to  start  with  controls  the  draught.  Aside  from  these  features  the 
desire  to  increase  output  acts  as  an  incentive  to  increase  both  the  speed 
and  the  draught  to  the  limit  the  material  will  stand.  There  are  many 
considerations,  however,  that  operate  to  hold  down  both  speed  and  draught 
below  that  which  will  do  injury  to  the  steel.  One  of  these  is  the  additional 
power  required  for  very  rapid  reduction;  another  is  the  severe  strain  on  the 
rolls  and  other  machinery  when  the  piece  enters  the  rolls  at  high  speed 
and  with  large  draught.  In  mills  composed  of  several  stands,  especially 


340 


THE  ROLLING  MILL 


iti  the  case  of  the  continuous  mill,  the  speed  of  all  preceding  stands  is  deter- 
mined by  the  speed  of  the  finishing  stand.  In  hand  mills,  the  speed  is 
restricted  to  the  highest  velocity,  about  six  hundred  feet  per  minute,  at 
which  the  catchers  can  grasp  the  piece  with  the  tongs.  The  magnitude  of 
the  draught  is  restricted  by  the  limiting  angle  at  which  the  rolls  will  "bite', 
the  piece  on  entering.  This  angle  is  found,  by  experience,  to  be  about  30°' 


FIG.  54.    The  Limiting  Angle  of  Rolling. 


Above  this  angle  the  resultants  of  the  forces  of  compression  have  receded 
so  far  from  a  parallel  to  the  line  joining  the  centers  of  the  rolls  that  they 
exert  a  push  on  the  piece,  and  the  resultant  of  the  forces  of  elongation  is  so 
nearly  vertical  that  the  horizontally  inclined  component  due  to  friction 
only  is  not  sufficient  to  balance  this  backward  push  and  drag  the  material 
between  the  rolls.  In  order  to  increase  this  limit,  a  series  of  horizontal 
and  well  rounded  grooves,  called  ragging,  are  often  cut  in  the  surface  of 
the  roll,  giving  it  the  appearance  of  a  half  formed  cog  wheel.  Since  these 
grooves  leave  ridges  in  the  material,  they  can  be  resorted  to  only  in  bloom- 
ing mills,  billet  mills,  or  roughing  stands.  Even  then  the  grooves  must  be 
cut  with  considerable  care  in  order  to  prevent  these  ridges  being  folded 
over  into  laps  in  succeeding  passes  and  rolled  into  the  material,  to  appear 
as  seams  in  the  finished  product. 

The  Effect  of  Diameter  of  Rolls:  From  a  study  of  Fig.  54,  it  will  be 
seen  that  the  larger  the  roll  diameters  are  the  greater  will  be  the  draught 
that  may  be  taken  without  exceeding  the  limiting  angle  of  rolling.  For  the 
same  draft,  however,  a  large  roll  gives  a  greater  roll  surface  area  in  contact 


EFFECT  OF  SIZE  OF  ROLLS  341 

with  the  metal  than  a  small  one  and  therefore  requires  more  pressure  to 
force  it  into  the  metal,  thus  putting  a  greater  tension  on  the  housings  and 
requiring  more  energy  to  drive  it.  The  large  roll  gives  an  affect  more  like 
that  of  pressing  than  the  small  roll,  and,  with  the  draft  and  speed  properly 
regulated,  the  effects  of  the  rolling  can  be  made  less  superficial  with  the 
large  roll.  The  large  roll  tends  to  cause  the  metal  to  spread  more  than 
the  small  roll.  Hence,  the  size  of  the  rolls  is  a  factor  to  be  considered  in 
designing  rolls  for  flats  and  other  products  in  which  the  spread  of  the  metal 
may  affect  the  dimensions  of  the  finished  article. 


342  PREPARATION  OF  STEEL 


CHAPTER  IV. 

PREPARATION  OF  THE  STEEL  FOR  ROLLING. 

SECTION   I. 

INGOTS   AND   THEIR   DEFECTS. 

Preparation  of  Ingots:  In  order  that  the  large  bodies  of  metal 
refined  at  one  time  by  the  various  methods  of  steel  making  may  be  obtained 
in  a  convenient  shape  for  rolling,  it  is  necessary  that  these  large  bodies 
be  divided  into  smaller  ones,  called  ingots,  of  a  uniform  shape  and  size. 
These  conditions  are  obtained  by  pouring  the  metal  while  it  is  still  molten 
into  moulds  of  the  desired  dimensions,  where  it  may  be  allowed  to  solidify 
in  part  or  in  whole  before  the  mould  is  removed.  Before  rolling  begins, 
however,  the  ingot  must  have  been  allowed  to  solidify  throughout,  and  the 
whole  mass  should  be  of  uniform  temperature.  But  in  cooling  naturally, 
these  conditions  are  not  fulfilled,  because  the  outside  of  the  ingot,  being 
the  part  from  which  the  heat  is  removed  the  most  rapidly,  is  the  first  to 
solidify.  With  this  fact  in  mind,  it  is  easily  understood  how,  in  any  case 
of  natural  cooling,  the  interior  is  the  last  to  drop  to  any  given  temperature. 
In  fact,  the  moulds  are  stripped  from  many  ingots  while  the  central  portion 
is  yet  in  the  liquid  state.  This  fact  was  early  recognized  by  steel  workers, 
and  so  it  was  originally  the  custom  to  strip  the  ingots  as  soon  as  possible 
and  place  them  in  a  tightly  covered  hole  or  pit  in  the  ground,  where  the 
heat  from  the  interior  of  the  ingot  was  slowly  conveyed  to  the  outside  by 
conduction,  and  sufficed  not  only  to  heat  up  the  colder  exterior  part  of  the 
ingot  but  also  to  supply  heat  to  the  pit,  which,  with  careful  manipulaton, 
was  sufficient  to  maintain  a  rolling  temperature.  This  process  was  called 
soaking,  hence  the  name  soaking  pit.  In  order  to  bring  the  soaking  under 
better  control  and  make  it  adaptable  to  varying  conditions,  means  for 
supplying  additional  heat  was  introduced,  so  that  the  modern  soaking  pit 
is  in  reality  a  kind  of  heating  furnace,  a  detailed  description  of  which  will 
be  given  later. 

Ingot  Defects:  A  prerequisite  to  faultlessly  finished  material  is 
perfect  ingots,  and  by  a  perfect  ingot  is  meant  one  free  from  all  cavities 
or  openings  and  made  up  of  material  that  is  homogeneous  throughout. 
Unfortunately,  the  natural  laws  that  govern  the  solidification  of  the  liquid 
metal  operate  against  both  these  requirements,  and  develop  the  well  known 
natural  defects  in  ingots  called  piping,  blow  holes,  segregation  and  crystal- 
lization. Added  to  these  are  other  defects,  both  incidental  and  accidental, 


INGOT  DEFECTS  343 


such  as  checking,  scabs,  and  slag  inclusions.  A  brief  discussion  of  these 
defects  follows;  but  an  understanding  of  their  causes  requires  a  study  of  the 
laws  that  control  the  cooling  of  ingots. 

The  Nature  of  the  Cooling  of  an  Ingot:  The  ingot  moulds  in  common 
use  are  tall  box-like  shapes  made  of  cast  iron;  they  are  open  at  both  ends, 
one  of  which  is  a  little  smaller  than  the  other  to  give  the  mould  a  little 
taper;  and  have  a  square  or  rectangular  section  slightly  rounded  at  the 
corners.  In  use,  one  end  of  the  mould,  usually  the  larger,  is  closed  by 
the  stool  on  which  the  mould  stands  in  an  upright  position.  Immediately 
the  molten  steel  is  poured  into  this  mold,  the  metal  next  to  the  mold  and 
stool  is  chilled  by  contact  with  the  cold  surfaces  and  solidifies  on  the  bottom 
and  sides  to  form  what  is  called  the  skin  of  the  ingot.  As  more  and  jnore 
heat  is  absorbed  by  the  mold,  this  skin  grows  in  thickness,  but  due  to  the 
increase  in  the  temperature  of  the  mold  and 'the  insulating  effect  of  the 
skin,  itself,  it  grows  at  a  rapidly  reduced  rate,  until  the  process  becomes 
so  slow  that  it  can  be  considered  as  a  normal  cooling.  The  cooling  then 
takes  place  by  a  dissipation  of  the  heat  through  this  skin  along  lines  per- 
pendicular to  the  surface  of  the  solidified  shell,  which  acts  as  the  conductor, 
with  the  result  that  this  shell  gradually  grows  in  thickness,  the  growth 
progressing  toward  the  center  until  all  the  metal  is  in  the  solid  state. 
The  laws  of  freezing  which  the  metal  obeys,  combined  with  this  manner 
of  freezing,  gives  rise  to  the  natural  defects  enumerated  above. 

Pipes:  One  of  the  most  noticeable  effects  of  the  freezing  is  the  pro- 
duction of  a  more  or  less  cone-shaped  cavity  at  the  top  of  the  ingot,  known 
as  the  pipe.  Pipes  are  the  result  of  the  contraction  of  the  metal  on 
solidifying  in  the  manner  just  described.  This  contraction  amounts  to 
about  two-hundredths  of  the  linear  dimensions  of  the  ingot,  and  if  the 
manner  of  cooling  did  not  set  in  play  forces  which  oppose  the  contraction, 
no  pipes  would  form,  and  a  perfect  ingot  would  measure  one-fiftieth  smaller 
than  the  mould  in  all  its  dimensions.  In  ordinary  ingots  much  of 
this  difference  in  volume  is  represented  by  the  pipe.  Since  the  skin  and 
the  more  slowly  formed  walls  built  up  by  the  cooling  are  rigid,  the  void 
left  by  contraction  is  filled  by  the  metal  in  the  central  portion  that 
still  remains  fluid,  the  force  of  gravity  directing  the  flow  downward  at 
all  times.  After  solidification  of  the  metal  is  complete,  further  contraction  on 
cooling  tends  to  open  this  pipe  still  farther  towards  the  bottom,  because 
the  exterior,  being  the  colder,  is  the  more  rigid  and  is  capable  of 
stretching  or  tearing  the  more  plastic  interior.  The  greater  portion  of 
the  surface  of  this  cavity  is  likely  to  become  more  or  less  oxidized, 
and,  since  the  oxidized  portion  is  not  welded  up  in  the  rolling,  the  pipe 
will  appear  in  the  smallest  rod  or  wire  into  which  this  part  of  the  ingot 
may  be  rolled.  Aside  from  injuring  material,  pipes  are  liable  to  cause 
accidents  in  rolling,  so  the  steel  maker  is  very  anxious  to  get  rid  of  them 
as  early  as  possible. 


344 


PREPARATION  OF  STEEL 


PIG  55.    Split  Ingots  Showing  Various  Forms  and  Degrees  of  Pipe. 


INGOT  DEFECTS 


345 


FIG.  55 — Continued. 


346  PREPARATION  OF  STEEL 

Methods  of  Reducing  Waste  due  to  the  Pipe:  Obviously,  the  only 
way  of  avoiding  this  pipe  is  by  discarding  the  portion  of  the  ingot  affected. 
Various  schemes  for  reducing  the  waste  due  to  this  cause  have  been  and 
are  being  tried,  and  some  of  them  are  fairly  successful,  among  which  the 
most  promising  seems  to  be  the  so-called  hot  top  mould.  As  explained 
in  connection  with  the  open  hearth  process,  in  one  form  of  these  moulds 
the  ingot  is  cast  with  the  smaller  end  down,  while  the  larger  end  is  sur- 
mounted with  a  short  mould  which  is  lined  with  refractory  and  non-con- 
conducting  material,  such  as  clay.  This  lining  reduces  the  size  of  the  top 
section  and  keeps  the  top  of  the  ingot  in  the  molten  state  until  the  ingot 
proper  has  solidified.  Thus,  the  pipe  is  brought  up  into  the  cope,  or  sink 
head,  which  is  of  much  smaller  section  than  the  ingot,  and  the  waste  due  to 
the  cropping  is  decreased  accordingly.  This  ingot  is  stripped  by  first 
removing  the  insulated  top  section,  gripping  the  sink  head  with  tongs  and 
then  lifting  the  ingot  out  of  the  mould.  In  a  patented  form  of  this  mould, 
known  as  the  Gathman  mould,  a  similar  effect  is  produced  by  decreasing 
the  thickness  of  the  mould  at  the  top.  Since  the  heavy  part  of  the  mould 
causes  a  more  rapid  cooling  than  the  thin  portion,  the  metal  at  the  top  is 
the  last  to  freeze. 

Blow  Holes:  In  the  molten  state  iron,  or  steel,  is  capable  of  dissolving 
large  volumes  of  gases,  such  as  oxygen,  carbon-monoxide,  nitrogen  and 
hydrogen,  this  solvent  power  increasing  with  the  temperature.  The  iron 
probably  unites  with  all  the  oxygen  immediately  it  is  dissolved,  hence  it 
is  retained  by  the  metal  in  the  solid  state  if  chemical  means  are  not 
employed  to  remove  it.  In  case  of  the  other  gases,  however,  no  such  stable 
combination  takes  place,  and  they  are  largely  thrown  out  of  solution  just 
previous  to  the  time  when  solidification  of  the  metal  occurs.  As  the  metal 
is  in  a  more  or  less  plastic  condition  at  this  time,  the  last  gases  thus  liber- 
ated may  not  be  able  to  escape  from  the  body  of  the  metal,  in  which  case 
they  collect  in  bubbles,  as  a  gas  will  in  making  its  way  out  of  any  fluid. 
Each  bubble  will  then  form  a  small  cavity  in  the  metal  which  is  known  as 
a  blow  hole.  These  holes  will  vary  in  size  from  those  visible  through  a 
microscope  to  large  pockets,  the  dimensions  of  which  can  be  measured  in 
inches.  The  smallest  ones  are  liable  to  occur  just  below  the  skin  of  the 
ingot  where  the  rapidly  cooling  metal  gave  the  tiny  bubbles  of  evolved 
gases  time  neither  to  escape  nor  to  collect  in  larger  bodies.  Here  the  gases, 
unable  to  escape  upward  on  account  of  the  very  viscous  nature  of  the 
metal,  form  tube-like  cavities  that  extend  at  right  angles  to  the  skin  wall 
of  the  ingot  and  toward  the  center.  In  the  rolling  of  the  steel,  the  blow 
holes  are  closed  up  and  welded  together  provided  their  surfaces  have  not 
been  oxidized,  in  which  case  they  will  not  weld  arid  will  produce  defects 
in  the  finished  articles.  Blow  holes  near  the  center  of  the  piece,  known 
as  deep  seated  holes,  are  less  liable  to  oxidation,  hence  are  the  least  harm- 
ful. But  the  small  blow  holes  beneath  the  skin  of  the  ingot  are  liable  to 
be  exposed  to  the  air,  or  be  filled  with  liquid  oxide  of  iron,  in  which  case 


INGOT  DEFECTS 


FIG.  56.     Transverse  Sections  of  Ingots  Showing  Blow  Holes 


348  PREPARATION  OF  STEEL 


they  produce  seams  in  the  finished  articles.  Blow  holes  are  an  ever 
present  menace.  But  correctives  may  be  employed  successfully,  and  they 
are  seldom  a  source  of  serious  damage  in  steel  that  has  been  properly 
worked  in  the  process  of  manufacture  and  thoroughly  deoxidized  at  the 
time  of  recarburizing.  In  this  respect  the  use  of  aluminum  in  the  mold  at 
time  of  casting  has  been  found  to  be  very  effective.  Blow  holes  have  the 
effect  of  reducing  the  size  of  the  pipe,  and  on  this  account  are  to  be  de- 
sired if  they  are  deep  seated.  Various  attempts  to  overcome  both  blow 
holes  and  pipes  mechanically  by  means  of  subjecting  the  metal  to  compre- 
ssion while  in  the  molten  state  have  been  tried,  but  the  expense  of 
operating  these  appliances  more  than  outweighs  the  good  derived, 
especially  since  the  steel  discarded  on  account  of  pipe  is  available  for  use 
as  scrap  in  the  open  hearth. 

Crystallization  is  the  property  possessed  by  iron,  in  common  with 
many  other  substances,  of  forming  crystals  on  solidifying.  The  size  of 
the  crystals  depends  on  the  composition  of  the  steel  and  the  rate  of  cool- 
ing; in  general,  the  slower  the  cooling  the  larger  the  crystals  will  be.  It 
is  plain  that  the  temperature  at  casting  and  the  size  and  shape  of  the 
ingot  and  mold  control  the  rate  of  cooling.  If  the  crystals  are  large,  the  force 
of  cohesion  among  the  crystals  is  decreased  by  the  increased  area  of  contact 
and  the  larger  size  of  their  cleavage  planes.  The  effect  of  unduly  large 
crystals  is  to  make  ingots  liable  to  tear  in  rolling.  This  condition  is 
sometimes  called  ingotism.  The  deformation  and  refinement  of  the 
crystals  in  rolling  prevents  their  effect  showing  up  in  finished  product  that 
has  been  properly  worked. 

Segregation:  Steel  is  a  mixture  of  various  compounds  and  elements; 
some  of  these  are  to  be  looked  upon  as  impurities  because  of  their  detri- 
mental effects,  but  others  are  necessary  to  impart  the  properties  most 
desired  in  the  product.  While  in  the  molten  state  these  solid  ingredients, 
like  the  gases  just  mentioned,  are  held  in  solution  by  the  iron,  a  power 
which  it  does  not  possess  to  the  same  degree  at  temperatures  below  its 
freezing  point.  Some  of  these  ingredients  freeze  at  a  lower  temperature 
than  the  iron.  Furthermore,  the  solution,  following  the  laws  of  selective 
freezing,  undergoes  a  series  of  changes  and  recombinations  with  the  formation 
of  various  eutectic  solutions,  which  increase  the  number  of  substances  that 
solidify  normally  at  much  lower  temperatures  than  pure  iron.  With  such 
an  aggregate,  it  is  easy  to  see  how  the  process  of  solidification  results  in 
an  isolation  of  the  ingredients.  Those  substances  having  the  highest 
melting,  or  freezing  points,  of  course,  are  the  first  to  crystallize.  This 
separation,  then,  has  the  effect  of  concentrating  the  solution  of  the  sub- 
stance having  the  lower  freezing  points  in  the  mother  liquor.  This  process 
continues  until  the  mother  liquor  is  made  up  only  of  that  substance  that 
has  the  lowest  freezing  point,  when  it,  too,  will  freeze,  forming  in  the  ingot 
a  solid  mass  very  different  in  composition  from  the  metal  that  crystallized 


INGOT  DEFECTS  349 


out  at  the  beginning.  Under  such  conditions,  it  is  to  be  expected  that  the 
substances  with  the  low  melting  points  would  be  found  in  one  spot  or  locality 
in  the  ingot  and  that  this  spot  would  be  located  near  the  top  and  center 
of  the  ingot,  that  is,  at  the  bottom  of  the  pipe,  where  the  metal  was  the 
last  to  freeze;  and  to  some  extent,  this  is  what  actually  does  occur,  so 
that  this  central  position  of  the  ingot  is  spoken  of  as  the  line  of  segregation. 
That  the  condition  is  not  even  more  pronounced  is  due  to  the  closing  in,  or 
entrapping,  of  the  small  pockets  of  the  mother  liquor  during  the  freezing 
and  to  the  high  viscosity  of  the  fluid.  Like  the  pipe  and  the  blow  hole, 
segregation  cannot  be  overcome,  but  by  rapid  cooling  and  the  use  of 
aluminum  to  quiet  the  metal  it  may  be  lessened  somewhat.  In  conclusion 
it  should  be  remarked  that  this  is  one  of  the  fundamental  reasons  why 
a  range  in  chemical  and  physical  specifications  is  imperative,  at  least  from 
the  manufacturer's  point  of  view. 

Checking  and  Scabs:  If  the  surface  of  a  mold  is  very  rough,  or 
contains  cavities,  so  that  resistance  is  offered  to  the  natural  contraction 
of  the  steel,  transverse  cracks  in  the  skin  of  the  ingot  may  result. 
However,  in  spite  of  all  precautions  that  may  be  taken  cracks  in  ingots 
will  occur,  and  a  study  of  this  matter  indicates  that  this  defect  is  more 
liable  to  occur  in  certain  grades  of  steel  than  ir  others,  and  particularly 
in  those  steels  in  which  the  carbon  content  is  between  .17%  and  .24%.  These 
cracks  become  oxidized  and  subsequently  produce  a  seamy  product. 
Scabby  material  is  often  caused  by  improper  pouring.  If  care  is  not  taken 
to  prevent  it,  the  metal  may  be  splashed  against  the  side  of  the  cold  mold 
during  the  pouring.  These  splashes  tend  to  stick  to  the  mold,  and, 
becoming  oxidized  on  the  surface,  will  then  appear  as  scabs  on  the  ingot 
after  it  is  stripped.  These  defects  very  often  show  up  after  rolling  in  the 
form  of  seams  and  slivers;  in  plates  they  will  form  serious  surface  defects. 
Such  defects  are  entirely  avoided  by  bottom  casting  the  ingots.  A  cracked 
mold  that  must  be  forcibly  drawn  by  the  stripper  may  produce  similar 
defects. 

Slag  Inclusions:  Various  explanations  are  offered  to  account  for  the 
presence  of  slag  particles  held  within  steel.  Slag  inclusions  may  be  due 
to  an  improperly  finished  bath,  or  in  case  the  furnace  practice  has  been 
good,  they  may  be  caused  by  slag  being  stirred  into  the  steel  and  mechani- 
cally held  by  it  while  the  heat  is  being  poured.  They  may  also  be  due 
to  dirt  in  the  ladle  or  molds,  or  they  may  be  the  result  of  slag  forming 
reactions  that  occur  during  the  deoxidation  of  the  metal  in  the  ladle  or 
molds.  The  latter  cause  would  seem  most  conducive  to  the  formation 
of  the  minute  slag  particles  that  occur  so  frequently  in  nearly  all  steels. 
Slag  particles  if  given  the  opportunity,  will  rise  to  the  top  of  the  metal  in 
the  ladle,  but  for  lack  of  time  small  particles  do  not  always  do  so.  Slag 
particles  remaining  in  steel  after  it  has  been  teemed  have  little  opportunity 
to  rise,  because  the  chilling  of  the  steel  by  the  mold  is  so  rapid,  and  they 


350 


PREPARATION  OF  STEEL 


FIG.  57.       Split  Ingots 


INGOT  DEFECTS 


351 


r- 


r 

•Ml 


Showing  the  Region  of  Greatest  Segregc 


352  PREPARATION  OF  STEEL 

are,  therefore,  entrapped.  Hence,  deoxidation  in  the  mold  should  be 
controlled  by  good  judgment  and  avoided  when  possible.  Large  slag 
inclusions  are  an  original  source  of  blisters  in  finished  products. 

Size  and  Shape  of  Ingots:  With  regard  to  the  size  of  ingots  a  number 
of  factors  operate  to  control  both  the  size  of  the  section  and  the  length. 
First  of  these  is  pouring  cost.  It  is  obvious  that  the  cost  of  teeming  a 
50-ton  heat  into  two-ton  ingots  will  be  much  greater  than  if  the  same  heat 
is  cast  into  four-ton  ingots  due  to  increased  number  of  molds  required, 
the  increase  in  scrap  produced,  and  the  longer  time  consumed  in  stripping 
and  charging  into  the  soaking  pits,  etc.  The  cost  of  rolling  may  be  in- 
creased, also,  for  a  long  ingot  may  be  rolled  with  the  same  number  of  passes 
as  a  short  one  of  the  same  section.  The  product  desired,  also,  is  a  factor 
in  determining  the  size  and  the  shape  of  the  ingot.  In  plate  mills,  for 
instance,  which  operate  independently  of  slabbing  mills,  the  size  of  the 
plate  to  be  rolled  determines  the  size  of  the  slab  ingot.  The  blooming 
and  slabbing  mills  and  their  equipment,  once  installed,  fix  a  limit  to  the 
size  of  the  ingot  both  as  to  section  and  length.  As  to  their  shape,  ingots 
may  be  of  any  convenient  form,  though  for  rolling  they  are  usually 
square  or  rectangular  in  section  with  rounded  corners.  These  forms  are 
easiest  on  the  steel,  as  the  flat  sides  offer  the  least  resistance  to  contraction 
on  cooling  and  the  rounded  corners  prevent  rapid  cooling  along  the  edges, 
which  would  result  in  cracks  from  subsequent  contraction  on  cooling.  For 
forging  large  rounds,  a  round  ingot  with  a  corrugated  surface  is  used. 
The  corrugations  permit  expansion  and  contraction  of  the  ingot  without 
the  danger  of  developing  cracks  that  are  liable  to  occur  in  the  surface  and 
interior  of  ingots  cast  in  a  perfectly  cylindrical  mould.  The  taper  on  in- 
gots is  to  facilitate  the  stripping.  To  express  the  size  of  a  rectangular 
ingot  the  dimensions  of  its  largest  section  are  always  given,  unless  other- 
wise specified.  Thus,  a  23}/£  inch  ingot  means  it  is  23^2  inches  square 
at  the  butt;  an  18%  x  21^  inch  ingot  means  it  is  rectangular  in  section  and 

x  21^  inches  at  the  butt. 


SECTION   II. 

THE   CONSTRUCTION  OF  THE   SOAKING  PIT. 

General  Features  of  the  Soaking  Pit:  The  soaking  pit  of  modern 
construction  is  so  built  that  it  can  be  used  either  as  an  old  time  pit  or  as  a 
heating  furnace.  Briefly,  soaking  pits  are  deep  chambers,  or  underground 
furnaces  of  square  or  rectangular  sections,  heated  by  the  regenerative 
principle  and  opening  at  the  top.  As  to  size,  they  are  built  large  enough 
to  contain  four,  six,  or  eight  blooming  mill  ingots  per  hole,  in  an  upright 
position.  The  older  furnaces  contain  four  ingots  per  hole,  while  the  capacity 
of  the  most  recent  ones  is  eight  ingots.  The  increase  in  size  is  due  mainly  to 
the  economy  in  fuel  which  is  obtained  by  the  use  of  large  pits.  While  the 
details  of  pit  construction  may  vary  somewhat  at  different  works,  yet  the 
form  and  principle  of  all  are  alike.  Therefore,  it  is  sufficient  to  study  but 
one,  which  may  serve  as  an  example  of  all.  For  this  purpose,  a  six  ingot 
furnace  at  Duquesne  will  be  described  somewhat  in  detail. 


THE  SOAKING  PIT  -       353 


Arrangement  of  the  Pits:  For  heating  the  ingots  for  the  two 
blooming  mills  at  these  works,  the  38-inch  and  40-inch  mills,  there  are  11 
rows  of  pits,  or  to  be  more  exact,  11  furnaces  of  4  holes  each.  The  holes  are 
numbered  1  to  44,  inclusive,  No.  1  to  No.  20  and  No.  37  to  No.  40  serve 
the  38-inch  mill;  the  other  16,  No.  21  to  No.  36,  inclusive,  serve  the  40-inch 
mill.  In  case  a  furnace  for  the  40-inch  mill  is  off  for  repairs  No.  5  furnace, 
containing  holes  17,  18,  19  and  20,  may  be  substituted.  The  first  nine 
furnaces  are  built  to  contain  six  22"  x  22"  ingots  per  hole,  but  numbers  10 
and  11  are  constructed  to  hold  eight  ingots  per  pit.  This  gives  a  pit  cap- 
acity for  the  40-inch  mill  of  96  ingots,  and  for  the  38-inch  mill,  184  ingots. 
The  furnaces  with  the  exception  of  No.  1,  are  built  in  groups  of  two  each. 
From  center  to  center  of  each  two  adjacent  furnaces,  the  distance  is  thirty- 
three  feet. 

Equipment  for  Handling  Ingots:  Spanning  these  soaking  pit 
furnaces  are  electric  traveling  cranes,  two  of  which  are  over  furnaces  No.  10 
and  No.  11,  and  four  are  over  No.  1  to  No.  9,  inclusive.  These  cranes  are 
Morgan  6-ton  machines,  and  are  equipped  with  Westinghouse  motors  as 
follows:  50  h.  p.  on  the  bricTge,  50  h.  p.  on  the  hoist,  10  h.  p.  on  the 
trolley,  and  5  h.  p.  on  the  tongs.  The  main  hoist  is  operated  by  a  gear 
hoist  and  shafting  rack.  The  tongs  are  connected  up  with  a  drum  on  a 
lifting  arm,  giving  a  vertical  movement  of  about  nine  and  one-fourth  feet. 
The  tongs  are  actuated  by  means  of  a  curved  groove  in  the  main  hoist  so 
that  their  distance  apart  may  be  varied.  The  tongs  are  equipped  with  four- 
inch  bits,  giving  a  distance  between  the  two  bits,  when  in  the  closed  or 
lowered  position,  of  sixteen  inches  and  when  in  the  raised  or  open  position  a 
distance  of  nineteen  and  five-eighths  inches.  Thus  the  largest  ingot  that  can 
be  gripped  is  one  about  eighteen  inches  at  the  top.  When  larger  ingots,  such 
as  the  22"  x  22"  size,  are  to  be  handled  it  is  necessary  to  remove  one  bit. 

Construction  of  the  Pits:  In  detail  the  construction  of  a  six-ingot 
soaking  pit  furnace  is  as  follows:  Each  furnace  or  pit  contains  four  rect- 
angular holes,  eight  feet  long,  five  feet  three  inches  wide  and  eight  feet 
seven  inches  deep.  These  holes  are  built  side  by  side  in  the  furnace,  and 
are  separated  only  by  firebrick  walls.  Each  hole  has  two  air  regenerators, 
one  on  each  side,  so  that  in  connection  with  each  furnace  there  are 
eight  regenerators.  The  holes  are  closed  by  firebrick  covers,  each  cover 
being  supported  on  four  wheels  which  roll  on  cast  steel  rails  lying  on  the 
division  wall  between  the  pits  and  fastened  at  their  ends  to  the  I-beams 
supporting  the  platform  about  the  pits.  The  walls  enclosing  the  checkers 
and  those  supporting  the  pit  proper  rest  on  a  concrete  foundation  twelve 
inches  thick.  These  walls  are  built  of  firebrick,  faced  on  the  outside 
with  river  brick.  The  outside  walls  are  about  eighteen  feet  high,  and  the 
river  brick  wall  directly  under  the  pit  is  about  eight  feet  high.  The  top  of 
this  river  brick  wall  is  protected  by  cast  iron  coping  plates.  Placed 
vertically  on  these  coping  plates  and  extending  up  into  the  firebrick 
bridgewall  are  cast  iron  end  plates.  On  the  coping  plates  rests  also  the 


354 


ROLLING  OF  STEEL 


Fia.  58.     Cross  Section  Drawing  of  a  Four-Hole  Six-Ingot  Soaking 
Pit  Furnace 


THE  SOAKING  PIT  355 


i 

steel  I-beams  supporting  the  cast  iron  pans  which  form  the  bottom  of  the 
pits.  A  pan  is  made  in  two  sections  with  a  semi-circular  hole  on  the 
inside  edge  of  each  section,  so  that  when  they  are  fitted  together  there 
will  be  a  circular  opening  about  ten  inches  in  diameter  through  which  the 
cinder  can  be  removed  from  the  pit.  Each  section  rests  on  three  ten-inch  I-- 
beams. About  one  foot  on  each  end  of  the  pan  is  flared  upward  at  an  angle 
of  45°.  There  are  five  cooling  boxes  resting  on  the  I-beams,  three  inside, 
or  intermediate  cooling  boxes,  and  two  end  ones.  The  inside  cooling  boxes 
are  in  the  division  walls  between  the  pits,  and  the  end  ones  are  in  the  end 
walls  of  the  two  outside  pits.  Each  of  these  boxes  rests  on  two 
I-beams.  The  boxes  are  hollow,  being  open  on  the  bottom,  and  the  lower 
half  of  the  end  of  the  bottom  is  cut  off  at  an  angle  of  about  45°.  Thus, 
these  cooling  boxes  and  pans  form  with  the  end  plates  a  triangular  space 
through  which  the  air  circulates  and  forms  the  air  cooling  system  for  the 
bridgewall.  On  the  top  of  the  cooling  boxes  and  near  each  end,  there  is 
a  four-inch  hole,  and  when  the  walls  between  the  pits  are  built  up,  this 
opening  is  extended  up  to  the  surface  so  that  a  circulation  of  air  is  main- 
tained through  it.  The  boxes  are  cast  iron,  one  inch  thick,  eight  feet  nine 
inches  long,  twenty-eight  inches  high  and  are  fourteen  inches  wide  inside 
at  the  bottom  and  four  and  three-fourths  inches  inside  at  the  top.  The 
pans  are  lined  with  nine  inches  of  firebrick  set  in  firebrick  mortar.  The 
cinder  hole  is  built  up  of  nine-inch  side-arch  brick.  The  pit,  then, 
to  above  the  slag  line,  is  lined  with  chrome  brick,  as  these  are  the  only 
bricks  that  are  not  fluxed  by  the  slag  formed.  Next  to  the  coolers,  however, 
there  is  one  four  and  one-half  inch  course  of  firebrick,  laid  in  fireclay,  but 
on  these  there  is  a  four-inch  course  of  chrome  bricks,  laid  dry,  and  at  the 
front  and  back  of  the  pits,  at  the  bridge  wall,  this  chrome  brick  lining  is 
nine  inches  thick.  There  are,  in  all,  seven  courses  of  chrome  bricks,  which 
brings  the  wall  even  with  the  top  of  the  cooling  box.  Above  this  level, 
the  walls  are  built  entirely  of  fire  brick.  The  side  of  the  bridgewall  next  to 
the  checker  chambers  is  capped  with  heavy  firebrick  tiles  (13^  x  6  x  2%") 
giving  a  width  to  the  firebridge  of  twenty-two  and  one-half  inches.  The 
chrome  bricks  are  heavily  coated  with  silica  slurry,  which  affords  an 
added  protection.  The  use  of  this  slurry  is  especially  important  on  the 
front  and  back,  for  the  bridgewall  is  the  weakest  part  of  the  furnace, 
because  it  is  subject  to  the  intense  heat  of  the  products  of  combustion 
leaving  the  pit  and,  therefore,  has  a  tendency  to  crack  and  spall.  The 
firebrick  part  of  the  walls  inside  of  the  pit  are  coated  with  a  slurry  of 
fire-clay.  This  coating  fills  up  the  cracks  and  forms  a  glaze  which  protects 
the  bricks. 

The  Air  Regenerators  are  about  six  feet  square  in  horizontal  section 
and  seventeen  feet  four  inches  deep.  The  sewer  which  conducts  the  air 
from  the  air  valve  to  the  two  chambers  on  the  same  side  and  farthest  from 
the  stack  is  beneath  the  air  sewer  for  the  two  pits  nearest  the  stack.  Thus, 
the  regenerator  chambers  and,  hence,  the  pits  are  fired  in  pairs.  The  bottom 


356  PREPARATION  OF  STEEL 

sewer  is  two  feet  seven  inches  high  and  the  arch  is  nine  inches  thick.  There- 
fore, the  regenerator  chambers  for  the  two  pits,  on  each  side,  nearest  the 
stack  are  three  feet  four  inches  less  in  height  than  the  back  chambers. 
Between  the  two  regenerators  on  the  same  air  flue,  starting  at  a  height  of 
about  five  feet  above  the  bottom  of  the  chambers,  there  is  an  eighteen  inch 
firebrick  wall  separating  the  two  adjacent  chambers.  The  two  pairs  of 
regenerators  on  the  different  air  sewers  are  entirely  separated  from  each 
other.  The  bottoms  of  the  chambers  are  separated  into  four  spaces  (four- 
teen and  one-half  inches  wide)  by  firebrick  withe  walls.  These  walls 
extend  back  into  the  air  sewer  to  the  air  valve  and  provide  for  the  even 
distribution  of  the  air.  On  these  withe  walls  there  is  one  course  of  firebrick 
tiles  on  which  the  checkers  rest.  The  withe  walls  are  three  feet  seven 
inches  high  in  the  two  pairs  of  regenerators  farthest  from  the  stack  and 
two  feet  four  inches  in  the  other  two  pairs,  thus  making  the  height  of  the 
first  mentioned  checkers  nine  feet  six  and  one-half  inches.  In  the  two  pairs 
of  chambers  farthest  from  the  stack,  the  checkers  extend  up  to  within 
thirty-one  inches  of  the  bridge  wall  and  in  the  other  two  pairs  to  within 
eighteen  inches.  The  top  row  of  checker  bricks  are  laid  so  that  the  openings 
are  in  the  same  direction  that  the  air  must  take  in  entering  the  pit.  The 
roof  of  the  regenerator  chambjer  is  arched,  being  built  of  firebrick  thirteen 
and  one-half  inches  thick,  but  the  arch  over  the  bridgewall,  for  a  distance 
of  twenty-seven  inches,  is  of  silica  brick  nine  inches  thick  and  laid  in  silica 
slurry  on  top  of  which  is  a  thirteen  and  one-half  inch  firebrick  arch. 
Silica  brick  is  used  in  this  construction  because  it  is  very  refractory  and 
can  withstand  a  heavy  load  when  highly  heated.  The  whole  furnace  is 
securely  tied  together  by  cast  iron  corner  binders,  tie  rods,  and  buckstays. 
Each  of  the  four  outside  corners  of  the  furnace  has  a  corner  binder  fifteen 
feet  ten  and  one-half  inches  high,  and  the  four  corners  directly  under  the 
pits  have  binders  eight  feet  one  inch  high.  These  binders  have  a  twelve 
inch  flange,  two  inches  thick,  provided  with  lugs  for  the  tie  rods.  The 
binders  are  connected  by  two  inch  tie  rods.  Along  the  two  outside  walls 
of  the  regenerators  there  is  a  structural  steel  buckstay,  the  ends  of  which 
are  connected,  across  the  furnace  end,  by  two  inch  tie  rods. 

The  Pit  Covers  consist  of  four  iron  castings  which  are  bolted  together 
and  are  held  rigid  at  the  center  by  a  cast  iron  separator.  Inclosed  in  this 
frame  is  a  firebrick  arch.  As  already  stated,  to  these  castings  are  fastened 
the  wheels  on  which  the  covers  roll.  To  each  separator  is  fastened  a  steel 
piston  rod  connected  to  the  piston  head  in  a  hydraulic  cylinder.  These 
cylinders  furnish  the  means  by  which  the  covers  are  moved.  In  some 
plants  the  covers  are  moved  by  lowering  the  tongs  into  a  special  box  in 
the  separator  casting  and  then  moving  the  crane  in  the  direction  desired. 
The  hydraulic  cylinders  operate  under  a  water  pressure  of  500  Ibs.  per 
square  inch.  They  rest  on  cast  iron  stands  fastened  to  the  floor  beams, 
and  the  bearings  for  the  cylinders  are  placed  about  the  center  of  the 
cylinders,  thus  making  them  free  to  rotate  about  this  point.  This  con- 


THE  SOAKING  PIT  357 


struction  is  made  necessary,  because,  as  the  furnace  becomes  old,  the 
dividing  walls  between  the  pits  sink  and  the  rails  bend.  Therefore,  the 
connection  of  the  piston  rod  and  the  separator  has  a  constantly  varying 
elevation  due  to  the  different  elevation  of  the  rails,  and  it  is  necessary  to 
have  the  cylinders  on  a  rocker  so  that  they  -may  follow  this  motion  and 
constantly  adjust  themselves  in  line  with  the  piston.  The  extreme  stroke 
of  the  cover  piston  is  nine  feet  nine  inches.  In  order  to  make  the  covers 
fit  nicely  the  tops  of  the  pits  are  surrounded  by  floor  plates  of  cast  iron. 

Fuel  and  Air  Valves,  etc.:  These  pits  were  built  to  use  natural  gas 
for  fuel,  but  this  fuel  has  been  replaced  by  coke-oven  gas.  When  natural 
gas  was  used  for  heating  the  pits,  it  was  admitted  through  the  roof  of  the 
regenerator  chamber  by  means  of  two  three-fourth  inch  pipes  twenty-one 
inches  long.  These  pipes  were  placed  at  such  an  angle  (about  four  and  one- 
half  inches  of  slope  per  foot)  and  distance  from  the  pit  that  the  flame  did 
not  play  directly  on  the  face  of  the  ingot,  and  a  reducing  atmosphere  could 
be  maintained  inside  the  pit.  The  pipes,  or  burners,  were  twenty-one 
inches  apart  and  were  fed  from  a  one  and  one-fourth  inch  pipe  which  in  turn 
was  connected  up  to  a  four  inch  gas  manifold  supplying  the  gas  to  the  four 
chambers  on  a  particular  side.  For  coke  oven  gas  it  was  thought  it  would 
be  necessary  to  modify  this  scheme  of  firing  somewhat  in  order  to  make 
the  conditions  suit  the  difference  in  the  heating  properties  of  these  gases, 
but  trial  runs  indicate  that  satisfactory  results  are  obtained  if  the  coke 
oven  gas  is  burned  in  the  same  manner  as  the  natural  gas.  For  re  versing 
the  direction  of  the  air  there  are  two  thirty-inch  Ahlen  sliding  valves,  and 
for  reversing  the  direction  of  the  gas  a  three-way  valve.  Each  set  of  valves 
consists  of  two  cast  iron  bed  plates,  two  cast  iron  sliding  plates,  two 
hydraulic  cylinders,  and  two  hoods.  The  distance  from  center  to  center 
of  the  hoods  is  five  feet  three  and  one-half  inches.  The  bed  plates  are 
bolted  together  and  the  cylinders  are  bolted  to  them.  Each  of  these  bed 
plates  has  three  openings  connected  to  flues,  of  which  the  two  outside  ones 
lead  to  the  regenerators  and  the  center  one  to  the  stack.  These  flues  are 
twenty-two  inches  wide,  the  division  walls  being  nine  inches  thick  and  the 
wall  between  the  two  sets  of  valves  twenty-two  and  one-half  inches  thick. 
As  to  the  sliding  plates  they  are  also  bolted  together  and  the  two  are  then 
connected  directly  to  the  piston  of  the  hydraulic  cylinder.  The  total 
length  of  the  sliding  plate  is  eleven  feet  one  inch.  Each  plate  has  six  open- 
ings, two  pairs  of  which  are  used  as  air  dampers,  while  the  other  two  form, 
with  the  hood,  a  part  of  the  flue  to  the  stack.  The  hood  rests  on  the  sliding 
plate,  and  both  the  hood  and  the  sliding  plate  are  water  cooled.  The 
hydraulic  cylinder  has  a  stroke  of  two  feet  seven  inches  and  a  plunger 
diameter  of  six  inches. 

Stack=Flues  and  Stack:  The  flues  leading  from  the  valve  to  the 
stack  are  three  feet  eleven  inches  high  and  twenty-two  inches  wide.  In 
these  flues  are  the  stack  dampers.  These  dampers  are  hand  operated  by 
means  of  a  chain  and  a  counter-weight.  They  slide  in  a  guide  frame  made 


358  PREPARATION  OF  STEEL 

in  the  form  of  a  casting  set  in  the  brick  work.  The  stacks  are  one  hundred 
three  feet  eight  inches  high,  and  consist  of  a  riveted  steel  shell  and  a  lining 
of  brick  work.  The  plates  of  which  the  shell  is  made  are  one-fourth  inch 
thick  at  the  bottom  of  the  stack  and  one-eighth  inch  at  the  top.  The 
outside  diameters  of  the  shell  at  the  top  and  bottom  are  respectively  four 
feet  six  inches  and  five  feet  ten  inches.  The  lining  consists  of  a  four  and 
one-half  inch  course  of  firebrick. 

The  Course  of  the  Gases  Through  the  Pits:  Of  the  two  thirty-inch 
air  valves,  the  one  nearest  to  the  pits  is  for  the  two  front  pits  and  the  other 
for  the  two  back  pits.  Thus,  for  the  two  front  pits,  the  air  enters  the  inside 
valve  through  the  top  sewer,  goes  through  the  two  front  regenerator 
chambers,  the  two  front  pits,  down  through  the  opposite  checkers,  through 
the  top  sewer,  through  the  inside  reversing  valve,  then  past  the  right  hand 
stack  damper  to  the  stack.  For  controlling  the  sliding  valve  so  that  the 
two  hoods  work  in  unison,  a  double-acting  Critchlow  valve  is  provided. 
Each  of  the  sliding  plates  is  provided  with  two  air  dampers  so  that  it  is 
impossible  to  shut  off  the  air  from  the  two  adjacent  pits  with  the  valves 
in  either  position.  The  gas  on  all  four  pits  is  reversed  by  one  three-way 
valve,  but  on  each  side  of  this  valve  there  are  four  other  valves,  so  that 
the  gas  can  be  shut  off  separately  on  any  pit.  To  reverse  the  direction  of 
the  gas  and  air,  the  gas  is  shut  off,  then  the  air  reversed,  and  after  it  the  gas 
is  reversed. 

Eight  Ingot  Pits:  The  main  difference  between  the  six  ingot  and  the 
eight  ingot  pits,  aside  from  increased  dimensions,  lies  in  the  fact  that  the 
air  regenerators  are  provided  with  a  special  division  wall.  This  wall  is 
built  parallel  to  the  end  of  the  pit  and  extends  to  the  top  of  the  checkers, 
the  object  being  to  retain  any  cinder  running  over  from  the  pit  in  the  first 
few  checker  openings,  thus  preventing  the  choking  of  all  but  a  few  of  the 
checker  spaces,  and  maintaining  a  higher  efficiency  of  the  regenerators. 
Also,  these  pits  are  provided  with  two  cinder  holes  instead  of  one  as  for 
the  six  ingot  holes.  The  furnaces  are  spaced  forty-one  feet  four  inches  from 
center  to  center,  and  the  holes  are  five  feet  three  inches  wide  and  ten  feet 
seven  inches  long,  and  are  spaced  eight  feet  three  inches  from  center  to 
center.  The  covers  on  these  pits  can  be  separated  about  two-thirds  of  the 
distance  from  the  back.  On  these  covers  the  piston  is  connected  to  the 
end  casting  of  the  cover  frame  instead  of  to  the  separator,  and  there  is  a 
separator  on  each  portion  of  the  cover.  When  closed,  the  separators  fit 
together  and  are  fastened  thus  with  hooks.  With  this  arrangement  it  is 
possible  to  move  the  entire  cover  or,  by  unhooking,  the  back  portion  only 
may  be  moved. 

Making  Up  the  Bottom  of  the  Pit:  Bottom  making  is  done  by  a 
group  of  men  called  the  bottom-makers,  who  are  provided  with  shovels, 
long  handled  pokers  and  cutters.  To  clean  out  a  pit,  the  pit  cover  is  pulled 
back  slightly,  and  a  shield  is  drawn  up  over  the  front  of  the  pit.  The  cinder 
hole  in  the  bottom  of  the  pit  is  then  opened  with  the  poker,  and  by  means 


SOAKING  INGOTS  359 


of  the  cutters  the  cinder  is  shoved  out  through  this  hole.  After  the  cinder 
has  been  removed,  a  piece  of  iron  sheeting  is  put  over  the  hole,  and  then 
the  process  of  making  bottom  is  begun.  Coke  breeze  from  the  blast  furnace 
coke  bins  is  used  to  make  up  the  bottom.  Coke  breeze  is  used  because 
it  absorbs  and  makes  fragile  the  molten  oxide  that  runs  off  the  ingot,  pro- 
tects the  brick  work,  and  helps  to  maintain  a  reducing  atmosphere  in  the 
furnace.  The  depth  of  the  coke  on  the  bottom  should  be  maintained  at 
about  eighteen  inches.  To  provide  the  desired  depth,  making  up  for  the 
coke  and  cinder  that  are  pushed  out  each  time,  requires  for  each  bottom 
six  to  eight  wheelbarrow  loads  of  breeze,  which  weighs  about  250  pounds 
per  barrow  load,  for  the  six  ingot  pits;  for  the  eight  ingot  pits  ten  to  twelve 
wheelbarrow  loads,  or  about  2500  pounds,  is  required.  This  coke  is  thrown 
in  from  the  front,  the  ends  being  made  up  first,  the  sides  next,  and  lastly 
the  center.  The  bottom  is  made  up  so  that  there  will  be  two  troughs  into 
which  the  ingots  may  be  placed.  The  object  in  providing  these  troughs 
is  to  keep  the  ingots  away  from  the  walls  so  that  they  will  have  a  better 
chance  to  heat  but  at  the  same  time  will  not  be  placed  so  near  the  center 
that  they  will  be  hit  directly  by  the  flame.  During  the  time  that  the 
bottoms  are  being  made  up,  the  gas  and  air  are  shut  off,  and  the  stack  is 
made  to  draw  air  through  the  cover  opening  so  that  the  heat  is  drawn  away 
from  the  men.  Before  charging  ingots  on  a  new  bottom,  the  coke  breeze 
should  be  allowed  to  become  well  heated  throughout,  as  a  cold  bottom  in 
the  pit  allows  the  butts  of  the  ingots  to  remain  cold,  and  when  ingots  are 
put  through  the  mills  in  this  condition  they  are  liable  to  break  the  rolls. 


SECTION  III. 

SOAKING  THE   INGOTS   FOR   ROLLING. 

Charging  the  Ingots:  Ingots  should  always  be  charged  into  the 
soaking  pits  in  an  upright  position,  which  explains  the  peculiar  construction 
of  the  pits.  There  are  two  reasons  for  this  method  of  charging.  First, 
the  best  practice  for  the  care  of  ingots  demands  that  they  be  stripped  as 
soon  as  possible  after  pouring  and  delivered  to  the  soaking  pits  before  they 
lose  much  of  their  original  heat,  because  the  hotter  they  are  charged  the 
quicker  will  they  reach  the  rolling  temperature,  and  little  fuel  for  reheating 
will  be  required.  In  pursuance  of  this  practice,  most  ingots,  except  high 
carbon,  high  sulphur  and  alloy  steels,  which  are  allowed  to  become  solid 
throughout  before  stripping,  reach  the  pits  while  their  central  portions 
are  still  molten  and  must,  therefore,  stand  in  an  upright  position  until  this 
portion  has  become  solid,  as  otherwise  the  extent  of  the  pipe  might  be  in- 
creased and  its  position  would  be  changed.  Second,  by  charging  ingots 
vertically  more  surface  for  ingress  and  egress  of  heat  is  exposed  to  the 
atmosphere  of  the  furnace,  thus  causing  them  to  come  to  a  uniform  rolling 
temperature  much  quicker  than  would  be  the  case  if  they  were  placed  in 
any  other  way. 


360  PREPARATION  OF  STEEL 

Heating  the  Ingots:  From  what  has  been  said,  it  is  easy  to  surmise 
that  great  injury  can  be  done  in  the  heating  of  the  ingots.  This  injury 
consists  of  under-heating,  over-heating,  uneven  heating,  or  worse  than  all, 
burning.  Of  these,  under-heating  and  over-heating  are  the  least  harmful 
to  the  steel;  the  former  increases  the  power  required  for  rolling  and  decreases 
the  time  permissible  for  the  rolling;  the  latter,  by  increasing  the  grain 
size  and  lessening  the  force  of  cohesion,  makes  the  steel  tender  and  liable 
to  crack.  Uneven  heating  increases  the  difficulties  of  rolling  very  much. 
A  cold  butt  of  an  ingot,  for  example,  may  cause  a  roll  to  be  broken.  Burning 
may  range  from  extreme  over-heating  to  a  temperature  just  below  the 
melting  point,  where  the  more  fusible  constituents  melt  and  run  out  of  the 
ingot,  forming  cavities  that,  on  rolling,  result  in  defects  that  will  be  cause 
for  rejection  of  the  material.  In  the  case  of  thin  skinned  ingots,  severe  over- 
heating may  have  a  like  result  by  exposing  the  blow  holes.  Besides  these 
general  precautions,  different  conditions  and  different  grades  of  steel  require 
different  treatment.  .  As  an  example  of  the  point  in  question  a  summary 
of  the  soaking  practice  as  carried  out  at  Duquesne  is  given  herewith. 

Week-End  Charges:  If  hot  steel  is  charged  Saturday  evening  just 
before  the  mill  shuts  down,  it  will  be  allowed  to  soak  until  one  or  two 
o'clock  Sunday  morning,  when  gas  will  be  admitted  for  about  an  hour. 
Soaking  will  then  be  continued  until,  the  day  turn  comes  out  at  seven  o'clock 
a.  m.  But  if  cold  steel  should  be  charged  before  the  week-end  shut-down, 
gas  is  admitted  for  three  or  four  hours,  the  flame  being  reversed  at  intervals 
of  from  one-half  to  one  hour;  and  the  steel  is  then  allowed  to  soak  until 
Sunday  morning.  During  the  soaking,  the  stack  and  air  dampers  are  kept 
closed. 

Soaking  Hot  and  Cold  Ingots:  To  bring  hot  steel  to  the  required 
rolling  temperature  requires  approximately  the  same  amount  of  time  as 
the  interval  between  the  time  the  heat  was  tapped  and  the  time  it  was 
charged  into  the  pits.  Hot  special  steel  of  medium  carbon  content  must 
be  in  the  pits  about  one  and  one-half  hours  and  spring  steel  about  one  hour. 
Thus,  the  period,  from  the  time  the  heat  is  tapped  at  the  open  hearth  until  it 
can  be  rolled,  is  about  three  hours  for  Duquesne  special,  about  two  hours 
for  spring  steel,  and  one  and  a  half  hours  for  ordinary  steel.  To  heat  six 
cold  soft  steel  ingots  in  the  6-ingot  pits  requires  about  six  hours.  For 
about  four  hours  after  the  pits  are  charged,  the  gas  and  air  may  be  admitted 
on  each  side  alternately  for  half  hour  periods.  The  period  of  reversal 
should  then  be  cut  to  fifteen  minutes.  Towards  the  last,  as  the  temperature 
of  the  steel  approaches  the  rolling  temperature,  the  period  of  reversal  may 
be  cut  to  five  or  ten  minutes,  for  the  more  frequent  the  reversal  the  more 
even  will  be  the  temperature  of  the  pits.  Cold  steel  is  very  rarely 
charged  in  the  ingot  pits,  the  practice  being  followed  only  after  a 
shut-down  when  the  mills  start  operating  at  the  same  time  as  the  open 
hearth,  for  at  such  a  time  there  is  no  hot  steel  on  hand.  The  period 
required  for  heating  cold  steel  in  the  eight  ingot  pits  is  about  eight  hours. 


SOAKING  INGOTS  361 


Soft  steel  is  heated  to  a  temperature  of  about  1200°  C.  (2200°  F.)  With 
both  high  and  low  carbon  steels,  should  only  four  or  five  ingots  be  charged 
in  the  smaller  pits,  the  period  required  for  heating  would  be  greatly  reduced. 
This  is  true  especially  for  the  low  carbon  steel,  for  with  only  four  ingots 
to  a  pit  it  is  possible  to  prepare  the  cold  steel  in  four  hours.  By  charging 
only  six  ingots  in  the  large  pits,  the  period  may  be  reduced  to  about  six 
hours.  Before  a  cold  high  carbon  heat  (.70%  carbon  or  over)  is  charged, 
the  pits  should  be  cooled  for  about  a  half  hour,  for  if  these  ingots  are  heated 
rapidly  they  are  liable  to  crack.  After  the  pits  have  been  cooled,  the  ingots 
are  charged,  and  sometimes  the  covers  are  left  open  for  a  half  hour,  so 
that  the  steel  will  be  heated  very  slowly.  The  period  between  reversals 
should  not  be  as  long  as  for  low  carbon  cold  steel,  and  so  at  first  the  reversals 
for  steel  of  this  grade  are  made  at  intervals  of  a  half  hour  or  less,  and  during 
the  balance  of  the  time  the  period  between  the  reversals  is  about  ten  minutes. 
The  rolling  temperature  of  spring  steel  is  about  1090°  C.  (2000°  F.) 

Soaking  Hot  Spring  Steel:  This  grade  of  steel  is  charged  in  a  hot 
pit.  The  gas  may  be  admitted  for  a  half  hour,  the  flue  being  reversed  every 
five  or  ten  minutes;  the  steel  should  then  be  allowed  to  soak  for  fifteen 
minutes,  and  then  gas  should  be  admitted  for  about  fifteen  minutes  to  bring 
up  the  temperature  of  the  outside  of  the  ingot.  This  steel  should  be  ready 
to  roll  in  about  an  hour.  While  the  steel  is  soaking,  in  addition  to  shutting 
off  the  gas,  it  is  best  to  shut  off  the  air  supply,  also,  for  the  effect  of  the 
hot  air  on  the  ingot  is  to  oxidize  or  even  to  burn  it.  If  the  steel  is  very 
hot  when  charged,  it  should  be  allowed  to  soak  for  a  half  hour  before  gas 
is  admitted;  then  gas  and  air  should  be  admitted  for  about  a  half  hour, 
with  reversals  every  five  or  ten  minutes.  The  steel  should  then  be  soaked 
for  a  half  hour  without  air,  and  then,  just  before  drawing,  the  temperature 
of  the  outer  part  of  the  ingot  should  be  brought  up  by  admission  of  gas 
and  air  again. 

Soaking  Low  Carbon  Hot  Steel:  Hot  low  carbon  steel  ingots  may 
be  heated  without  danger  for  a  half  hour,  the  direction  of  the  gas  and  air 
being  reversed  every  fifteen  minutes.  The  steel  should  then  be  allowed  to 
soak  for  fifteen  minutes,  and  before  drawing  the  outside  temperature  should 
be  raised.  Since  there  is  not  as  much  danger  of  burning  this  steel  as  there 
is  with  the  high  carbon  grades,  it  is  not  always  necessary  to  close  the  air 
dampers  during  the  time  the  steel  is  soaking. 

Soaking  Medium  Steels :  The  practice  with  respect  to  medium  steels, 
.30%  to  .60%  carbon,  is  to  heat  the  ingots  to  about  the  same  temperature 
as  for  low  carbon  steel.  The  steel,  if  charged  hot,  should  be  ready  to  roll 
in  one  hour  after  charging. 

Soaking  Screw  Stock:  High  sulphur  steel  is  charged  as  quickly  as 
possible  after  stripping.  The  time  required  to  heat  it  is  about  one  and  a 
half  hours.  The  steel  is  heated  to  dripping,  that  is,  until  the  scale  melts 
and  flows  readily  from  the  surface,  and  is  rolled  when  in  that  condition. 
Owing  to  the  high  sulphur  content,  it  is  necessary,  to  maintain  good  practice 


362  PREPARATION  OF  STEEL 

in  rolling,  to  heat  it  very  hot,  so  that  the  steel  will  be  very  plastic.  This 
condition  is  obtained  only  at  a  very  high  temperature,  about  1240°  :C. 
(2240°  F.).  Since  these  screw  stock  ingots  are  heated  until  they  are  dripping 
a  large  amount  of  liquid  cinder  is  always  formed,  so  that  it  is  necessary 
to  add  a  little  coke  in  the  pits  after  every  heat  of  this  kind  to  absorb  this 
cinder. 

Soaking  Alloy  Steels:  Nickel  steel  is  heated  to  about  the  same 
temperature  as  spring  steel,  1090°  C.  Chrome  vanadium  is  heated  to  about 
1250°  C.  Copper  steel  is  heated  according  to  its  carbon  content  in  much 
the  same  way  as  carbon  steels. 

Drawing  the  Ingots:  The  craneman  draws  the  ingots  from  the  pits 
according  to  the  orders  of  the  heater.  Usually,  a  definite  order  is  followed; 
at  Duquesne  the  regular  method  is  to  draw  the  two  front  ingots  from  each 
of  two  holes,  then  the  two  middle  ones  from  each  of  the  two  holes,  and  then 
the  two  back  ones  from  each  of  the  two  holes.  The  operation  is  then  repeated 
on  the  next  two  holes.  However,  the  operation  may  be  varied;  the  two 
front  ones  in  each  of  four  holes  may  be  drawn,  thus  affording  more  time  for 
the  middle  ingots  to  heat  while  the  others  are  being  drawn.  To  transfer 
the  ingots  from  the  pits  to  the  blooming  mill  tables  three  pot  cars,  two  of 
which  are  extras,  are  provided.  These  cars  are  operated  by  19  h.  p. 
Westinghouse  motors.  At  the  38-inch  mill  they  are  controlled  and  dumped 
from  the  manipulator  of  the  mill,  but  on  the  40-inch  mill,  the  man  that 
operates  the  pit  covers  controls  the  movement  of  the  car.  When  the  car 
receives  an  ingot  it  is  run  to  the  first  table  roller,  and  there  the  car  is  tipped, 
when  the  ingot  falls  upon  the  table. 

Heat  Balance  of  Pits:  That  the  soaking  of  ingots  is  an  expensive 
process  is  evident  from  the  equipment  required.  The  cost  of  the  up-keep 
of  this  apparatus  is  high,  and  the  efficiency  is  very  low,  even  on  up-to-date 
furnaces,  as  the  following  heat  balances  as  determined  by  experiment  on 
some  Duquesne  furnaces  using  natural  gas  will  show: 

Table  50.    Data  Relative  to  the  Efficiency  of  Soaking  Pit  Furnaces. 

Sensible  Heat  in  Steel  Charged 619,701  B.  t.  u. 

Heat  of  Combustion  of  the  Gas 781,808 

Heat  Carried  in  by  Regenerated  Air 384,970 


TOTAL 1,786,479 

Heat  in  Steel  when  Drawn 773,597  B.  t.  u. 

Heat  in  Gases  Entering  Stack 173,862 

Heat  Given  up  to  Regenerators 386,329 

Radiation  and  Unaccounted  for  Losses 452,691 


1,786,479 

,,.,  ^ffi  .  Heat  Absorbed  by  Steel  153,896    0  R0f 

Pit  Efficiency= = =8.6% 

Total  Heat  Delivered  to  Furnace  1,786,479 


DISPOSITION  OF  INGOTS 


363 


Disposition  of  Ingot  Products:  Since  the  ingot  is  the  starting  point 
for  all  mechanical  working,  it  is  interesting  to  trace  the  material  through 
the  various  processes  that  the  steel  undergoes  to  produce  the  many  articles 
in  which  it  is  used.  For  this  purpose  the  following  table  has  been  prepared, 
and  requires  little  by  way  of  explanation.  Each  dash  marks  a  reheating 
of  the  material,  while  each  word  means  a  mill,  or  a  set  of  mills,  where 
work  is  done  to  produce  the  article  named. 

Table  51.     Disposition  of  Steel  from  Ingots. 

Universal  Mill  Plate. 
Armor  Plate. 

Bloom,  Sheet  Bar— Sheets. 
Shaped  Bloom,  Large  Shapes. 

(Universal  Mill  Plates. 
Slabs— j  Eye  Bars. 

[Sheared  Plates. 
fRods. 
Bars. 

Bloom,  Billet— {  Bands. 
Hoop. 
[Small  Shapes. 

fRods. 

Ingots — \  Small  Shapes. 

Billet—  Bars. 
Bands. 

Seamless  Tube. 
.  Sheet  Bar— Sheet. 

Rectangular  BloomH  Structural  Shapes. 
Rails. 
Rail  Joints. 
Q1    .       /Tube. 
Skelp-(pipe. 
Forgings. 
(Wheels. 
Cylindrical  Blooms— { Circular  Shapes. 

[Shell. 
Large  Forgings. 


364  THE  ROLLING  OF  STEEL 


CHAPTER  V. 

THE  ROLLING  OF  STEEL— BLOOMS  AND  SLABS. 

SECTION  I. 

INTRODUCTORY. 

Outline  of  the  Plan  of  Study:  Rolling  mills  are  somewhat  like 
houses.  Thus,  while  they  are  alike  as  to  gross  features,  they  differ  greatly 
as  to  details  of  construction.  Just  as  the  architect  will  strive  to  impart 
individuality  to  a  building,  so  the  rolling  mill  engineer  and  builder  will 
endeavor  to  introduce  new  ideas  looking  to  greater  improvements  in  con- 
struction; and  just  as  it  is  desirable  to  adapt  a  building  to  its  location  and 
surroundings,  so  is  it  found  necessary  to  alter  the  details  of  mill  construction 
to  suit  the  conditions,  local  and  otherwise.  The  result  of  all  these  influences 
on  mill  construction  has  been  to  produce  such  a  variation  in  mills  that 
there  are  no  two  mills  exactly  alike.  Evidently,  to  describe  all  the  details 
of  mills  and  their  operations  is  well  nigh  an  endless  task;  yet  it  is  desirable 
that  the  reader  be  given  an  opportunity  to  become  so  well  acquainted  with 
the  rolling  of  each  product  that  he  will  be  more  or  less  familiar  with  the 
more  essential  details  of  its  production  and  thoroughly  understand  the 
conditions  under  which  it  is  produced.  The  plan  decided  upon  as  best 
to  pursue  is  this:  An  attempt  will  be  made  to  describe  the  rolling  of  as 
many  products  as  possible,  and  in  doing  so  the  order  followed  will  be 
from  the  rolling  of  material  from  ingots,  to  semi-finished  products,  to 
finished  products,  as  indicated  in  the  previous  diagram.  In  this  con- 
nection one  mill  rolling  the  material  in  question  will  be  described,  as  well 
as  the  operation  in  detail;  after  which  the  product  itself  will  receive  special 
attention.  In  describing  mills,  the  details  of  one  mill  of  each  type  or  class 
will  be  given.  As  a  sort  of  working  outline  of  the  plan,  the  following  classi- 
fication of  mills  will  give  an  idea  of  the  ground  to  be  covered  and  the 
order  in  which  the  subjects  are  to  be  treated.  The  general  discussion 
preceding  this  part  of  the  study  should  supply  information  to  fill  in  any 
gaps  that  may  occur  in  the  studies  to  follow. 


BLOOMS  AND  SLABS  365 

Table  52.     Classification  of  Mills. 

A.  Mills  Rolling  Material  from  Ingots. 

1.  Semi-finishing  Mills: 

a.  Blooming  (Cogging)  Mills. 

b.  Slabbing  Mills. 

2.  Finishing: 

a.    Universal  Plate  Mills. 

B.  Mills  Rolling  Material  from  Blooms  and  Slabs. 

1.  Semi-finishing: 

a.  Billet  Mills. 

b.  Sheet  Bar. 

c.  Skelp. 

2.  Finishing: 

a.  Plate  Mills: 

i.     Sheared, 
ii.     Universal. 

b.  Rail  Mills. 

c.  Structural  Shape  Mills. 

d.  Wheel  Mills— Schoen  Mill. 

e.  Wheel  and  Circular  Shape  Mills. 

C.  Mills  Rolling  Material  from  Billets. 

1.     Merchant  Mills. 

a.  Guide  Mills. 

b.  Bar  Mills. 

c.  Hoop  or  Strip  Mills,  etc. 

Blooms,  Slabs  and  Billets:  As  a  preliminary  step  toward  forming 
steel  into  the  various  sections  which  its  many  uses  require,  the  heavy 
ingots,  except  in  certain  plate  mills  and  some  large  shape  mills,  are  first 
roughly  reduced,  in  mills  especially  designed  for  the  purpose,  to  much  lighter 
but  still  very  simple  sections,  as  the  round,  the  square  and  the  rectangle. 
When  the  ingot  has  been  reduced  to  the  dimensions  of  a  square  between 
one  and  one-fourth  inches  and  six  inches  it  is  cut  into  convenient  lengths, 
called  billets ;  if  these  pieces  are  six  inches  square  or  larger,  they  are  known 
as  blooms :  and  if  reduced  to  rectangular  forms  but  with  widths  which  are 
less  than  twice  the  thickness  and  within  the  dimensions  specified  for  the 
square,  the  same  names  apply.  But  if  the  width  far  exceeds  the  thickness 
of  the  rectangular  section,  then  it  is  called  a  slab.  If  the  output  of  the  mill 
is  mainly  blooms,  it  is  called  a  blooming  mill  in  the  United  States  or  a 
cogging  mill  in  England;  if  billets,  a  billet  mill;  and  if  slabs,  a  slabbing  mill. 
The  blooming  and  slabbing  are  the  largest  and  strongest  mills  used  to  roll 
steel,  if  the  mills  that  roll  heavy  armor,  of  which  there  are  no  longer  any 
in  this  country,  be  excepted.  The  reasons  for  the  existence  of  these  mills 
are  evident. 


THE  ROLLING  OF  STEEL 


SECTION   II. 

SOME    GENERAL  FEATURES   PERTAINING  TO   BLOOMING   MILLS. 

Size  of  Blooming  Mills:  The  size  of  blooming  mills  is  popularly 
supposed  to  be  based  on  the  diameter  of  the  rolls,  or  on  the  distance  from 
center  to  center  of  the  rolls.  Both  these  quantities  are  constantly  changing, 
due  to  the  wearing  of  the  rolls,  which  affects  their  diameters,  and  to  the 
fact  that  they  are  adjustable.  The  size  is,  therefore,  based  on  the  distance 
from  center  to  center  of  the  pinions,  which  corresponds  to  the  distance 
from  center  to  center  of  the  rolls  and  also  to  their  diameters,  and  is  always 
constant.  The  blooming  mills  in  use  at  the  present  time  will  range  in  size 
from  twenty-eight  to  forty-six  inches.  The  older  mills  are  the  smaller, 
because  it  was  formerly  the  practice  to  cast  the  ingots  much  smaller  than 
at  present,  and  large  mills  were  not  required.  The  size  of  ingots  having  been 
gradually  increased  for  the  reasons  already  pointed  out,  the  size  of  the 
mills  designed  to  roll  them  were  necessarily  increased  also.  This  size  seems 
now  to  have  approached  a  standard,  and  most  mills  of  recent  construction 
have  rolls  in  the  neighborhood  of  forty  inches  in  diameter. 

Types  of  Bloomers,  Their  Advantages  and  Disadvantages :  Bloom- 
ing mills  are  of  three  general  types,  namely,  reversing,  continuous,  both 
of  which  are  two=high,  and  three=high.  Of  these,  two-high  reversing  and 
three-high  mills  are  the  most  common.  As  an  example  of  the  continuous 
blooming  mill,  the  billet  mill  at  Gary,  Ind.,  is  cited.  It  consists  of  nine 
stands  of  rolls  arranged  in  tandem  and  separately  driven  by  electric  motors. 
Since  its  blooms  are  delivered  directly  to  a  continuous  billet  mill,  the 
reduction  of  the  ingot  to  billets  is  made  in  one  continuous  operation.  The 
chief  advantage  in  this  arrangement  is  an  extraordinarily  large  output. 
As  to  reversing  and  three-high  bloomers,  each  of  these  types  has  its 
advantages  and  disadvantages,  some  of  which  it  may  be  of  interest  to 
enumerate  here.  The  main  advantage  of  the  reversing  mill  over  the  three- 
high  lies  in  its  greater  flexibility.  Thus,  the  top  roll  being  adjustable, 
various  sizes  of  blooms,  billets  or  slabs  can  be  rolled  on  one  set  of  rolls,  and 
the  draught  can  be  regulated  to  suit  steel  at  different  temperatures  and  of 
different  grades.  Even  different  methods  of  reducing  the  ingot  may  be 
employed  with  the  same  rolls.  On  long  lengths  the  two-high  mill  is  to  be 
preferred  on  account  of  the  greater  ease  with  which  such  material  can  be 
handled,  while  the  simplicity  of  the  roll  design  is  also  a  factor  in  favor  of 
these  mills.  On  the  other  hand,  a  reversing  mill  is  a  much  more  expensive 
mill  than  a  three-high  mill.  In  the  first  place  the  tonnage  is  much  lower. 
On  two-high  forty  inch  mills  the  average  output  is  about  2000  tons  per 
twenty-four  hour  day,  to  produce  which  about  2500  tons  of  ingots  are 
required,  while  a  three-high  mill  of  the  same  size  will  roll  almost  twice  as 
much  steel.  Again,  the  power  equipment  of  the  reversing  mill  is  costly 
and  the  loss  of  power  is  great.  Reliable  tests  show  that  the  total  power 


BLOOMS 


367 


368  THE  ROLLING  OF  STEEL 

developed  by  a  reversing  mill  engine  is  distributed  about  as  follows: — 

27%  used  in  overcoming  idle  friction  of  the  engine  parts. 
9%  used  in  overcoming  pinion  and  spindle  friction. 

13%  used  in  overcoming  roll  journal  friction. 

21%  used  in  overcoming  the  acceleration  of  the  parts  in  reversing. 

30%  used  in  actually  deforming  the  steel. 

In  three-high  mills  where  the  rotation  is  in  one  direction  only,  there 
is  no  acceleration  loss,  besides,  by  the  use  of  a  flywheel,  lighter  engines 
than  those  used  on  the  reversing  mill  may  be  used  to  do  the  same  work. 
Efficiency  tests  on  three-high  mills  show  that  about  85%  of  the  total  power 
developed  by  the  engine  is  used  in  driving  the  mill,  and  the  idle  friction 
of  the  mill  parts  is  about  15%,  thus  leaving  nearly  70%  of  the  motive 
power  developed  available  for  deforming  the  steel. 

Drive  for  Reversing  Mills:  Since  the  lengths  dealt  with  on  blooming 
mills  are  relatively  short,  the  speed  of  the  rolling  is  slow,  but  as  the 
material  is  heavy  and  the  pull  is  great,  though  the  draughts  are  only 
moderately  heavy,  great  power  is  required.  Hence,  most  of  the  older 
reversing  blooming  mills  are  indirectly  driven,  that  is,  they  are  connected 
to  the  engine  through  large  gears  which  enable  the  engine  to  travel  at  a 
higher  speed  than  the  mill.  The  power  is  thus  multiplied  by  a  number 
equal  to  the  speed  ratio.  This  speed  ratio  will  vary  in  the  different  mills 
from  as  high  as  three  to  one  to  as  low  as  one  to  one,  while  many  mills,  of 
which  the  thirty-eight  inch  bloomer  at  Homestead  and  the  forty  inch 
mills  at  Clairton  and  Duquesne  are  examples,  are  direct  driven.  A  few 
reversing  mills  installed  since  1914  are  driven  by  reversing  electric  motors. 
These  motor  installations  are  very  complicated.  They  consist  of  a  main 
motor  and  a  motor-generator  set,  which  prevents  the  acceleration  loss 
peculiar  to  the  steam  driven  reversing  mill  and  raises  the  efficiency  of  the 
mill  considerably. 

SECTION  III. 
AN  EXAMPLE  OF  REVERSING  MILLS— THE  40"  MILL  AT  DUQUESNE. 

The  Engine  for  this  mill,  which  is  driven  direct,  is  of  the  twin  tandem 
compound  condensing  type,  but  is  operated  non-condensing.  It  was  made 
by  Mackintosh-Hemphill  &  Co.  Its  size  is  44"  x  70"  x  60"  and  its  maxi- 
mum horse  power  is  rated  at  20,000.  The  maximum  torque  at  the  circum- 
ference of  a  thirty  inch  roll  is  465,000  inch-pounds.  The  engine  may  run  at 
any  speed  up  to  140  r.  p.  m.,  but  the  maximum  speed  during  rolling  is  about 
130  r.  p.  m.  The  exhaust  steam  is  discharged  into  a  feed  water  heater. 
The  throttle  is  controlled  from  the  pulpit  located  about  thirty  feet  in  front 
of  the  rolls  and  directly  over  the  roll  tables. 

Driving  Connections:  A  cast  nickel-steel  crab  of  six  pods  is  keyed 
onto  the  crankshaft  of  the  engine;  it  is  four  feet  five  inches  in  diameter. 
Over  it,  and  held  in  place  by  wooden  stretcher  blocks  is  fitted  the  large 
end  of  a  cast  nickel  steel  compound  coupling  box,  which,  at  this  end,  is 
three  feet  two  inches  in  diameter.  The  driving  spindle  from  this  coupling 


TWO-HIGH  BLOOMING  MILL  369 

is  five  feet  eleven  and  one-fourth  inches  long  and  is  supported  by  a  cast 
steel  coupling  carrier  resting  at  its  four  corners  on  standard  spiral  car 
springs  of  12500  pounds  capacity,  which  stand  eight  and  one-fourth  inches 
high  when  free,  seven  and  one-fourth  inches  at  4700  pounds  load,  and  six 
and  nine-sixteenth  inches  when  fully  compressed.  The  springs  in,  turn  rest 
on  cast  steel  seats  bolted  to  special  cast  iron  shoes  which  are  anchored  to 
the  shoes  carrying  the  pinions  and  housings.  The  carriers  are  lined  with 
one  inch  of  babbitt  metal.  The  mill  end  coupling  box  is  two  feet  four  and 
one-half  inches  in  diameter  and  is  cast  to  fit  over  the  four  pods  of  the  engine- 
end  wobbler  of  the  bottom  mill  pinion. 

Pinions  and  Pinion  Housings:  The  pinions  are  of  the  staggered 
straight  tooth  type  and  are  made  of  nickel  steel,  approximately  of  a  com- 
position as  shown  by  the  following  analysis:  Carbon,  .29%;  manganese, 
.66%;  phosphorus,  .020%;  sulphur,  .030%;  and  nickel,  2.97%.  Their  average 
life  is  253,575  tons  of  steel  rolled.  The  top  and  bottom  pinions  are  similar 
and  hence  interchangeable.  Each  one  is  ten  feet  six  inches  long  over  all 
and  four  feet  ten  inches  between  the  necks,  which  are  twenty-one  inches  in 
diameter.  This  diameter  is  further  reduced  to  twenty  and  one-half  inches 
at  the  wobblers.  The  pitch  diameter  is  forty  inches,  and  the  number  of 
teeth  is  fourteen.  The  pinions  run  in  solid  cast  steel  babbitted  bearings, 
the  bottom  of  which  are  beveled  to  fit  on  the  sills  of  the  window  of  the 
cast  iron  pinion  housings.  The  pinion  housings  are  bolted  to  the  mill  shoes, 
are  nine  feet  six  inches  high,  and  have  windows  2'  7W  wide  by  1'  6%" 
deep;  the  windows  are  lined  with  one  and  one-fourth  inch  forged  steel 
liners  held  in  place  by  stud-bolts  through  the  housings.  A  cast  steel  housing 
cap,  to  which  is  attached  the  hydraulic  cylinder  used  for  lowering  the  top 
roll  of  the  mill,  is  fastened  over  the  housings  by  means  of  key  bolts.  The 
bearings  are  each  two  feet  six  inches  wide  and  twenty  inches  from 
front  to  back  and  may  be  adjusted  by  set  pins  reaching  through  the  housings. 
The  top  bearings  rest  directly  on  top  of  the  bottom  bearings  unless  plate 
liners  are  used  in  between  them  to  get  the  proper  pitch  for  the  teeth.  The 
bearings  are  held  down  tight  by  keying  the  cap  on  tight  and  using  liners 
between  it  and  the  top  bearing  if  necessary. 

Spindles  and  Coupling  Boxes:  Over  the  mill-end  wobblers  of  the 
pinions  are  fitted  cast  steel  coupling-boxes  uniting  the  wobblers  with  the 
spindles.  The  coupling  boxes,  of  cast  steel,  are  two  feet  six  inches  in  diam- 
eter and  twenty-two  and  one-half  inches  wide,  and  cast  to  fit  over  the  four 
pods  of  the  spindles.  The  bottom  and  top  spindles  are  each  ten  feet  long 
and  twenty-one  inches  in  diameter  where  they  rest  on  their  carriers.  The 
bottom  spindle  is  provided  with  wobblers  twenty  and  one-half  inches  in 
diameter  and  two  feet  in  length,  and  is  nineteen  inches  in  diameter  at  the 
center  between  the  two  carrier  bearings.  On  the  top  spindle  the  wobblers 
are  nineteen  inches  in  diameter,  thirteen  and  seven-eighths  inches  long  and 
are  curved  at  the  ends  to  permit  the  mill  end  to  ride  up  or  down  with  the 
top  roll.  Twenty-three  inches  at  the  center  of  the  top  spindle  is  turned 


370  THE  ROLLING  OF  STEEL 

smooth  to  a  diameter  of  twenty-one  inches  to  give  a  bearing  for  the  spindle 
carrier,  which  is  movable.  The  bottom  spindle  rests  at  two  points  near 
its  ends  on  two  stationary  spindle  carriers  bolted  to  the  mill  shoes.  The 
carrier  for  the  top,  or  vibrating,  spindle  consists  of  a  cradle  formed  by  two 
cast  steel  arms  hung  at  their  engine  ends  from  two  supporting  rods  pivoted 
on  spring-supported  bolts  which  pass  through  supporting  brackets  bolted  to 
the  pinion  housings.  In  the  center  of  the  carrier  is  a  rest  for  the  spindle, 
and  on  its  mill  end  the  carrier  is  supported  by  the  carrier  bearing  for  the 
top  roll,  being  fastened  to  this  bearing  by  a  forged  steel  pin.  A  coupling- 
box  similar  to  those  used  with  the  pinions  fastens  the  bottom  spindle  to 
the  bottom  roll;  seven-eighths  of  an  inch  clearance  is  allowed  at  each  con- 
nection between  spindle  and  pinion  or  roll,  respectively.  For  the  top 
pinion,  a  light  coupling  box  is  used  in  order  that  it  may  act  as  a  safety  for 
the  mill  by  breaking  under  excessive  strain  before  any  other  part  of  the 
mill  is  damaged.  This  box  is  twenty-two  and  one-half  inches  in  width, 
twenty-five  and  three-fourths  inches  in  outside  diameter,  and  two  and  one- 
quarter  inches  in  thickness  at  the  thinnest  point.  The  other  boxes  are 
four  inches  thick.  All  coupling  boxes  are  held  in  place  by  iron  or  wooden 
stretcher  blocks  fastened  in  place  by  steel  or  leather  straps. 

Roll  Housings:  The  roll  housing  on  the  engine  side  of  the  mill  is  set 
with  its  center-line  fourteen  feet  six  and  one-quarter  inches  from  the  center 
line  of  the  mill-end  pinion  housing,  a  cast  iron  separator  and  steel  bolt 
holding  these  two  housings  in  line.  This  housing  is  cast  steel  but  in  other 
respects  is  the  same  as  the  outside  housing,  which  is  made  of  cast  iron. 
Both  are  bolted  to  the  mill  shoes  and  stand  twelve  feet  three  inches  high 
above  them;  they  are  set  with  their  center  lines  seven  feet  eleven  inches 
apart  and  are  held  in  line  by  two  cast  iron  separators  and  steel  bolts,  one 
at  the  front  and  one  at  the  back.  Besides  the  mill  rolls  the  housings  also 
support  four  feed  rollers,  two  on  each  side  of  the  rolls,  sixteen  inches  in 
diameter  and  five  feet  ten  and  one-eighth  inches  long.  The  windows  of  the 
housings  are  three  feet  five  and  one-half  inches  wide,  nine  feet  deep,  and 
begin  two  feet  ten  inches  below  the  top  of  the  housing.  In  the  top  of  each 
housing  is  left  a  hole  for  the  housing  nut,  which  is  made  of  brass.  Through 
these  nuts  the  housing  screws  for  adjusting  the  top  roll  are  inserted.  The 
nuts  are  larger  at  the  bottom  than  at  the  top;  they  are  twenty  inches  in 
diameter  at  bottom,  sixteen  inches  at  top,  and  thirty-four  inches  high. 
They  are  shrunk  into  the  housings,  and  over  them  are  fastened  small  caps, 
twenty-seven  inches  high,  on  which  the  screw  pinions  rest.  The  housing 
screws,  the  bottom  ends  of  which  press  directly  down  on  the  screw  brasses 
in  the  cast  iron  breaker  blocks  on  the  rider  bearing  boxes  of  the  top  roll, 
are  made  of  .60%  carbon  open  hearth  steel,  eight  feet  three  inches  long  and  ten 
inches  in  diameter;  the  threads  have  a  pitch  of  two  inches.  They  must 
allow  a  lift  of  twenty-five  inches.  These  screws  are  provided  with  octagon 
heads.  Fitted  about  the  heads  are  steel  pinions  which  rest  on  the  top  of 
the  screw  caps.  The  pinions  have  a  pitch  of  two  and  one-quarter  inches, 
a  pitch  diameter  of  fifteen  and  eighty-two-hundredths  inches,  a  face  of 


TWO-HIGH  BLOOMING  MILL  371 


eight  inches,  and  twenty-two  teeth.  The  pinions  are  operated  through  a 
gear  mounted  on  a  spider  which  has  a  pitch  diameter  of  eighty-three  and 
nine-hundredths  inches,  a  pitch  of  two  and  one-fourth  inches,  a  face  of  seven 
inches,  and  one  hundred  sixteen  teeth,  and  is,  in  turn,  operated  by  means 
of  a  pinion  fastened  to  its  shaft.  This  latter  pinion  has  a  pitch  diameter 
of  twelve  and  fifty-four-hundredths  inches,  a  pitch  of  three  inches, 
a  face  of  ten  inches,  and  thirteen  teeth,  and  is  operated  by  a  rack  with  a 
three  inch  pitch  and  a  ten  inch  face.  This  rack  is  connected  up  to  the 
hydraulic  cylinder  located  on  the  top  of  the  pinion  housing.  Attached  to 
the  rack  is  the  finger,  which,  moving  over  a  gauge,  provides  an  indicator 
for  the  size  of  the  pass.  The  screws  of  the  mill  are  required  to  lift  twenty- 
five  inches,  but  a  ten  foot  stroke  of  the  rack  will  give  the  screws  a  vertical 
movement  of  twenty-eight  and  one-half  inches,  the  extra  length  of  stroke 
allowing  for  the  wear  of  the  roll  necks  and  bearings.  In  rolling,  this  gauge 
can  be  set  to  give  correct  readings  on  one  pass  only,  and  to  gauge  the  other 
passes  it  is  necessary  to  add  or  subtract  a  certain  quantity  from  the  gauge 
reading.  A  cast  iron  bridge  is  bolted  to  the  top  of  the  housing  and 
serves  both  to  support  the  spider  and  to  keep  the  housings  properly 
spaced.  The  housings  are  further  supported  and  kept  in  line  at  the  top  by 
two  cast  iron  separators  and  two  steel  bolts. 

Rolls:  The  top  and  bottom  rolls  in  this  mill  are  alike;  there  are  two 
in  a  set,  and  each  roll  weighs  26,000  pounds.  A  typical  analysis  of  the  rolls 
gives  the  following  results:  .61%  carbon,  .75%  manganese,  .010%  phos- 
phorus, .030%  sulphur.  Their  dimensions  are:  Total  length,  twelve  feet 
ten  inches;  length  of  body,  six  feet;  diameter  of  wobbler,  twenty  and  one- 
half  inches;  diameter  of  necks,  twenty-two  inches;  diameter  of  collars, 
thirty-three  and  one-eighth  inches.  They  have  five  passes,  the  widths  and 
diameters  of  which  are  24"x31#",  12"x29>6",  8"x29%",  6"x29#", 
4"  x  29%".  The  rolls  are  ragged  only  in  the  twelve  inch  and  eight  inch 
passes,  and  here  the  ragging  is  only  one-sixteenth  of  an  inch  deep;  all  passes 
are  roughened  sli  ghtly  with  knurling  wheels.  These  rolls  are  changed  every 
week  and  dressed  in  the  roll  shop.  About  three-sixteenths  of  an  inch  is 
taken  off  each  time  they  are  dressed,  and  when  the  collars  have  been  cut 
down  to  thirty  and  one-half  inches,  the  rolls  are  scrapped.  Four  sets  are 
kept  on  hand,  and  one  set  is  used  once  in  four  weeks,  giving  a  life  of  about 
one  year  per  set.  The  average  tonnage  is  82,650  tons  for  each  set  of  rolls. 

Roll  Bearings:  The  bottom  roll  rests  with  each  neck  on  a  babbitt 
lined  cast  steel  bearing,  two  feet  six  inches  wide,  twenty-one  and  three- 
fourths  inches  from  front  to  back,  and  six  and  three-fourths  inches  thick  at 
the  base;  its  bottom  is  made  to  fit  the  sill  of  the  window,  and  its  top  is  cut 
out  at  a  twelve  inch  radius  with  one  and  one-quarter  inches  of  babbitt  to 
fit  the  neck  of  the  bottom  roll.  Sheet  steel  shields  are  placed  over  the 
necks  of  the  bottom  roll  to  keep  scale  from  getting  between  the  necks  and 
bearings.  The  top  roll  is  carried  in  two  cast  steel  carrier  bearings,  which 
in  turn  are  supported  each  by  two  three  and  one-half  inch  square  steelyard 


372  THE  ROLLING  OF  STEEL 

rods.  These  rods  are  mounted  in  sockets  hung  from  counterweighted  arms 
underneath  the  mill,  the  rods  coming  up  through  the  housings  and  bottom 
bearings  on  each  side  of  the  necks  of  the  bottom  roll.  The  carrier  bearings 
are  three  feet  three  inches  wide,  twenty-three  and  three-fourths  inches  from 
front  to  back  ancj  are  six  inches  thick  at  the  base.  They  are  flat  on  the 
bottom  and  concave  at  the  top  with  a  twelve  inch  radius  and  babbitt  metal 
one  and  one-fourth  inches  thick.  On  the  engine  side  of  the  inner  bearings 
are  two  lugs  for  receiving  the  pin  to  hold  up  the  spindle  carrier.  The  rider 
bearing  of  the  top  roll  is  cast  steel  two  feet  two  and  one-half  inches  wide, 
twenty-one  and  three-fourths  inches  from  front  to  back,  and  two  and  one- 
fourth  inches  thick,  with  one  inch  of  babbitt  metal.  It  is  concave  below 
at  a  radius  of  twelve  inches  and  beveled  on  top.  The  bearing  box,  also  of 
cast  steel,  is  of  the  same  dimensions  as  the  bottom  bearing,  except  that  it 
is  seven  inches  thick.  It  is  beveled  underneath  to  receive  the  top  bearing 
and  is  flat  on  top.  On  it  rests  the  cast  steel  breaker  block,  into  which 
the  housing  screw  fits.  The  breaker  blocks  are  protected  by  brasses, 
which  are  placed  in  sockets  on  the  tops  of  the  blocks. 

Hydraulic  Shears:  Immediately  beyond  the  forty  inch  mill  delivery 
table,  begins  the  No.  1  shear  table,  delivering  to  a  hydraulic  bloom  shears. 
This  table  is  thirty-one  feet  long,  and  consists  of  fourteen  cast  steel  rollers, 
twelve  inches  in  diameter  and  five  feet  eleven  and  one-quarter  inches  wide. 
These  are  driven  by  a  Westinghouse  30  h.  p.  220  volt  series  wound  D.  C. 
motor,  controlled  either  at  the  bloom  or  the  billet  shears.  At  the  end  of 
this  table  is  an  emergency  shear.  It  is  a  vertical  hydraulic  shear,  using  water 
at  500  pound  pressure  to  the  square  inch;  the  plunger  is  forty-two  inches  in 
diameter  with  a  nineteen  inch  stroke..  The  bottom  shear  knife  is  the 
one  actuated  by  the  plunger;  the  knives  are  twenty-seven  inches  wide  and 
four  inches  thick.  As  this  is  an  emergency  shear,  it  is  rarely  used. 

Steam  Shears :  No.  2  shear-table  is  immediately  beyond  the  hydraulic 
shears  and  has  thirty-six  driven  rollers,  and  one  idler,  all  similar  to  those 
at  No.  1  shear-table,  except  the  last  two,  which  are  collared  on  one  end. 
The  rollers  are  driven  by  a  Westinghouse  50  h.  p.  220  volt  series  wound  D.  C. 
motor  controlled  at  the  steam  shears.  This  table  delivers  the  blooms  and 
slabs  to  the  steam  shears,  the  center  of  which  is  ninety-two  feet  ten  and  one- 
half  inches  beyond  the  hydraulic  shears.  A  bloom  stamping  machine  is 
located  on  this  table  midway  between  the  two  shears;  it  is  of  the  idler  wheel 
type  and  is  held  in  place  hydraulically.  The  steam  shears  are  driven  by  a 
MacKintosh-Hemphill  18"  x  20"  simple  vertical  steam  engine,  the  driving 
shaft  of  which  is  meshed  with  the  shears  by  a  hydraulically  operated  clutch. 
These  shears  are  also  vertical  acting,  the  top  knife  blade  being  driven 
down  to  meet  the  fixed  lower  one.  The  knives  are  twenty-seven  and  one- 
half  inches  wide  and  three  inches  thick,  and  the  top  one  has  a  ten  and  three- 
fourths  inch  stroke.  The  steam  shears  are  equipped  with  a  gauge  and 
stopper  for  cutting  a  number  of  pieces  the  same  length;  the  stopper  can  be 
set  to  cut  lengths  from  twelve  inches  to  one  hundred  thirty-six  inches, 


TWO-HIGH  BLOOMING  MILL  373 

inclusive,  in  quarters  of  an  inch;  the  piece  to  be  cut  is  run  through  the  shears 
onto  the  rear  table,  which  is  sixteen  feet  long  and  consists  of  sixteen 
hollow  cast  steel  rollers,  ten  inches  in  diameter.  It  is  driven  through 
universal  joints  by  a  Westinghouse  19  h.  p.  220  volt  series  wound  D.  C. 
motor  and  can  be  tilted  at  its  receiving  end  hydraulically  to  inove  down 
with  the  shear  knife.  For  pieces  forty  inches  long  or  less,  it  is  moved 
nearer  the  shears  to  prevent  the  piece  from  falling  into  the  pit  for  butt  ends. 
Beyond  this  table  is  the  loading  table  for  blooms  and  slabs;  it  is  seventeen 
feet  long  and  has  sixteen  hollow  cast  steel  rollers  eight  inches  in  diameter. 
It  is  driven  from  a  line  shaft  by  the  same  type  of  motor  as  the  shears  rear 
table.  Halfway  down  this  table  on  its  inner  side  is  a  steam  kicker  with  a 
seven  inch  by  four  feet  nine  inch  cylinder,  which  slides  the  bloom  down 
a  chute  to  the  buggies  on  the  tracks  below.  A  hydraulic  stopper  is  located 
at  the  end  of  this  table.  Crop  ends  or  scrap  can  be  run  over  the  end  of  the 
table  to  charging  boxes  below  the  end  of  it.  Six  feet  six  inches  beyond 
the  end  of  this  table  begins  the  receiving  table  of  a  fourteen  inch  continuous 
mill. 

Manipulator:  All  reversing  mills  are  provided  with  manipulators  for 
turning  the  ingot  as  desired  between  the  passes,  for  moving  the  piece  from 
groove  to  groove  and  for  straightening  it  as  it  enters  the  passes  of  the  mill 
when  such  straightening  is  necessary.  They  are  located  under  the  roll 
table,  and  near  the  rolls  on  the  entering  side  of  the  mill.  They  are  of  various 
forms.  The  manipulator  for  this  mill  consists  of  two  parallel  sets  of  five 
fingers  each,  and  has  both  a  vertical  and  horizontal  movement.  The  frame 
is  beneath  the  table  rolls  and  rests  on  a  bottom  frame  which  is  supported 
on  four  heads,  connected  to  the  arms  of  bell  cranks.  These  cranks  are 
supported  on  a  bed  plate  and  are  connected  up  by  stretcher  rods  to  a 
hydraulic  lifting  cylinder,  which  has  a  stroke  of  fourteen  and  three-fourths 
inches.  This  ratio  of  the  length  of  the  crank  arms,  however,  increases  this 
lift  to  eighteen  inches.  On  this  frame  are  five  rails  to  form  a  track 
for  the  wheels  of  the  upper  frame  which  is  moved  horizontally  by  means 
of  a  hydraulic  cylinder.  In  the  lowest  position,  the  fingers  are  five  inches 
below  the  top  level  of  the  roll  tables;  in  the  highest,  they  extend  thirteen 
inches  above  it. 

Design  of  the  Rolls:  All  reversing  blooming  mill  rolls  are  designed 
with  slight  collars  between  the  passes  in  order  to  control  the  spreading  of 
the  material  under  the  heavy  reduction,  as  otherwise  the  material  may 
spread  so  far  at  the  surface  as  to  cause  a  protrusion,  or  fish  tailing,  of  the 
metal  at  the  edges,  which,  becoming  folded  over,  would  cause  laps.  To 
prevent  the  collars  from  cutting  into  the  steel  and  thus  forming  laps  all 
the  passes  except  the  finishing  are  given  a  slight  belly.  A  fillet  at  the  base 
of  the  collars  serves  to  keep  the  corners  of  the  piece  well  rounded.  The 
ragging  on  the  rolls  to  increase  the  bite  has  already  been  referred  to.  As 
to  arrangement  of  the  passes,  different  plans  may  be  pursued,  as  may  be 
seen  from  a  study  of  the  accompanying  drawings.  The  first  two  designs 


374 


THE  ROLLING  OF  STEEL 


J 

I  -                      J 

]             10    r 

i 

, 

00         s 

N         1 

nn 

BLOOMS 


375 


are  for  blooms,  billets  or  slabs,  whereas  the  third  design  can  roll  large 
blooms  only  and  billets  only  in  connection  with  a  roughing  mill. 

In  the  method  shown  in  table  53  and  fig.  60  the  reduction  is  begun  with  the 
ingot  on  edge,  but  when  rolling  soft  steel,  .08%  to  .22%  carbon,  the  ingots  are 
sometimes  rolled  on  the  flat.  This  reduces  the  number  of  passes  to  seventeen, 
the  steel  receiving  only  four  passes  in  the  first  groove.  In  rolling  blooms 
of  other  sizes  and  slabs,  about  the  same  procedure  is  followed  out,  the  steel 
being  given  a  sufficient  number  of  passes  to  work  it  down  to  the  required 
size.  In  rolling  some  of  the  special  steels,  such  as  special  drop  forgings, 
etc.,  it  is  often  the  practice  to  turn  the  steel  after  each  pass  in  order  to 
avoid  all  danger  of  rolling  in  laps  and  seams.  Sometimes  where  fairly  sharp 
corners  are  desired  on  the  blooms  they  are  given  extra  passes  to  hold  the 
edges  up.  This  extra  rolling  is  especially  necessary  where  the  blooms  are 
to  be  reheated  in  a  continuous  furnace,  since  if  the  corners  are  very  rounded 
the  blooms,  instead  of  sliding  down,  are  liable  to  roll  over  the  skids  in  the 
bottom  of  the  furnace.  Furthermore,  if  the  steel  shows  a  tendency  to 
crack,  the  roller  may  nurse  it  along  by  taking  lighter  drafts. 

Operation  of  Rolling:  The  sketch  referred  to  above  shows  how  an 
18"  x  21"  ingot  is  broken  down  to  a  6"  x  4"  bloom  in  nineteen  passes.  This 
sketch,  combined  with  the  following  table,  gives  about  all  the  information 
there  is  to  give  on  this  part  of  the  work. 

Table  53.    The  Rolling  of  an  18"  x  21"  Ingot. 


No.  OF 
GROOVE 

SIZE  OF 
GROOVE 
ON  ROLL 

No.  OF  PASSES 
AND  MANIPULATION 

18"  x  21"  INGOT 
REDUCED  TO 

1 

24" 

2 

18^"  x  19"      Bloom 

—Bloom  turned  90° 

1 

24" 

4 

12"      x  19^"       " 

—Bloom  turned  90° 

2 

12" 

4 

ll%"  x  12^"       « 

—Bloom  turned  90° 

2 

12" 

2 

7M"xl2M"       • 

—Bloom  turned  90° 

3 

8' 

2 

7^"  x    8M"      \ 

—Bloom  turned  90° 

- 

3 

8" 

2 

4"      x    8" 

—Bloom  turned  90° 

5 

4" 

1 

6K"x    4^"       " 

—Bloom  turned  90° 

4 

6" 

1 

5^"x    4^"       « 

—Bloom  turned  90° 

4 

6" 

1 

4"     x    6"           a 

—  Finish 

19  Passes 

376 


THE  ROLLING  OF  STEEL 


*T 

H 


*-«¥6— I 
^^ 


KIT 


IP 


BLOOMS 


377 


T 

IT" 

-T- 

r 

1 

I 

i 

|M 

% 

cS 

i 

8 

1 

( 

i 

i 

1 

i 

—           V    f^-L 

^ 

I 

c~!2J*-> 

r-  8"  4 

----.24"  •» 

«-   I3|'/- 

-  9|"H 

s 

Sf"- 


FIG.  62.    Another  Design  for  40-inch  Two-High  Reversing  Blooming  Mill  Bolls. 


Top  and  bottom  rolls  have  same  dimensions 
FIG.  63.    A  38-Inch  Reversing  Blooming  Mill  Designed  to  Roll  a  Fixed  Size  of  Bloom. 


SECTION   IV. 

EXAMPLES   OF  THREE-HIGH  BLOOMING   MILLS. 

Plan  of  Study:  Since  a  good  idea  of  the  relative  dimensions  of  the 
different  parts  of  the  blooming  mill  may  be  gained  from  the  preceding 
detailed  description  of  the  forty  inch  mill  at  Duquesne,  such  details,  for 
the  sake  of  brevity,  may  now  be  omitted,  and  the  description  of  the  forty 
inch  three-high  mill  at  Edgar  Thomson  be  made  more  general  with  the  idea 
of'  emphasizing  the  difference  in  construction  and  operation  between  the 
two-high  and  the  three-high  blooming  mills,  only. 


378  THE  ROLLING  OF  STEEL 

The  Engine  and  Connections:  A  tandem  compound  condensing 
engine,  size  50"  x  78"  x  60",  furnishes  the  driving  power  for  the  mill.  The 
engine  is  housed  in  an  engine  room  separate  from  the  mill.  It  is  provided 
with  a  75-ton  flywheel,  twenty-five  feet  in  diameter,  and  runs  at  a  speed  of 
54  r.  p.  m.  This  flywheel,  supported  between  suitable  bearings,  is  mounted 
upon  the  driving  shaft,  which  is  connected,  by  means  of  a  crab  and  coupling 
box  to  the  driving  spindle.  This  spindle  is  nine  feet  eight  and  one-half 
inches  long,  including  ten  inches  at  each  end  for  the  wobblers,  and  twenty- 
one  and  three-fourths  inches  in  diameter.  It  is  supported  at  its  center 
by  a  stationary  carrier  bearing,  and,  extending  through  the  wall  of  the 
separate  engine  room,  connects  the  driving  shaft  of  the  engine  to  the  middle 
pinion  of  the  mill. 

The  Pinions  and  Spindles:  The  pinions,  contained  in  three-high 
housings  similar  to  the  roll-housings,  are  six  feet  four  inches  long  over  all, 
and,  when  in  place,  measure  forty  inches  from  center  to  center  of  any  two 
adjacent  ones.  The  lengths  of  the  necks  are  twenty-one  inches  and  their 
diameters  are  twenty-two  inches.  These  pinions  are  of  the  herring  bone, 
or  helical  toothed  type.  Unlike  the  reversing  mill,  where  the  use  of  a 
vibrating  spindle  makes  it  necessary  to  set  ^the  pinions  at  some  distance 
from  the  mill,  the  three-high  mill  will  be  set  with  the  pinions  as  close  as 
possible  to  the  rolls;  the  roll  spindles  are,  consequently,  much  shorter. 
The  spindles  for  this  mill  are  four  feet  ten  and  three-fourths  inches  long 
over  all,  and  twenty-one  and  three-fourths  inches  in  diameter.  Each 
spindle  is  supported  at  its  center  by  means  of  a  bearing  mounted  on  a  bar 
that  bridges  the  space  between  the  inside  roll  housing  and  the  opposite 
pinion  housing.  Specially  designed  coupling  boxes  connect  the  spindles 
with  the  pinions  and  the  rolls. 

The  Roll  Housings  are  of  the  open  top  type.  At  the  top  the  window 
of  the  housing  is  closed  with  a  heavy  cap,  which  is  securely  fastened  to 
the  columns  of  the  housing  by  means  of  heavy  key  bolts,  the  slotted  ends  of 
which  extend  up  through  and  above  the  ends  of  the  cap.  The  screw  down 
passes  downward  through  the  center  of  the  cap  and  rests  on  the  top  of  the 
upper  bearing  of  the  top  roll,  so  that  the  pressure  may  be  applied  directly 
over  its  center.  The  rigidity  of  the  housings  is  increased  by  the  use  of 
brace  rods  which  extend  from  a  height  about  the  center  of  the  top  roll, 
both  fore  and  aft,  to  an  anchorage  provided  by  projections  on  the  shoes. 
The  two  housings  are  tied  together  by  means  of  separators  and  bolts  on 
front  and  back  attached  just  below  the  caps  of  the  housings,  so  that  they 
are  almost  on  a  level  with  the  upper  side  of  the  top  roll.  In  width  the 
housings  measure  seven  feet  eight  inches  from  center  to  center  of  the  shoes, 
and  are  approximately  fourteen  feet  high  from  the  lowest  point  in  the  base 
to  the  top  of  the  cap. 

The  Rolls  are  all  of  the  same  length  and  diameter  of  neck.  The  lengths 
of  the  bodies  are  seventy-six  inches,  while  the  dimensions  of  the  necks  and 


THREE-HIGH  BLOOMING  MILL 


THE  ROLLING  OF  STEEL 


wobblers  are  the  same  as  for  the  same  parts  of  the  pinions.  As  to  the  diam- 
eters of  the  bodies,  the  three  rolls  are  made  different,  the  top  roll  being 
the  smallest  and  the  bottom  roll  the  largest  and  the  middle  roll  of  an  inter- 
mediate size.  These  diameters  are  such  that  the  distance  between  the 
centers  of  new  rolls  on  new  bearings  is  forty  and  fifteen-sixteenths  inches 
for  the  bottom  and  middle  rolls  and  thirty-nine  and  eleven-sixteenths  inches 
for  the  middle  and  top  rolls.  This  arrangement,  the  necessity  for  which 
will  be  explained  later,  has  the  effect  of  throwing  the  rolls  slightly  out  of 
line  with  the  pinions  which  measure  forty  inches  from  centers  to  centers. 
This  difference  is  distributed  by  centering  the  bottom  roll  five-sixteenths 
inch  below  the  center  of  its  pinion  and  the  top  roll  five-sixteenths  inch 
above  the  top  pinion.  The  center  of  the  middle  roll  is  then  five-eighths 
inch  above  that  of  the  middle  pinion.  The  rolls  are  designed  for  seven 
passes  as  shown  on  the  accompanying  sketch.  The  ingot,  having  been 
reduced  from  23%"  x  23%"  to  15^"  x  18^"  by  four  passes  on  a  forty-eight 
inch  two-stand  tandem  bloomer,  enters  the  first  bottom  pass  of  the  forty- 
inch  mill  on  edge  and  is  reduced  in  this  and  the  six  succeeding  passes  to  a 
9^"  x  9J^"  bloom.  Hence,  all  the  mills  of  the  plant  using  blooms  from 
this  mill  are  adjusted  to  take  this  size  of  bloom.  It  will  be  observed  that 
the  edges  of  the  collars  are  well  rounded  off  to  prevent  the  formation  of 
fins  that  might  cause  laps,  and  that  the  pitch  line  for  the  bottom  passes 
lies  well  below  the  clearance  line  of  the  rolls.  The  bottom  and  middle 
rolls  are  made  of  steel,  while  the  top  roll  is  a  sand  roll.  The  greater  strength 
of  the  two  lower  rolls  is  required  for  the  greater  draught  taken  in  the  bottom 
passes,  which  are  edging  passes. 

Lifting  Tables:  The  mill  is  provided  with  two  lifting  tables,  each  of 
which  is  twenty-one  feet  seven  and  nine-sixteenths  inches  long  from  center 
to  center  of  the  first  and  last  rolls.  Each  table  has  a  vertical  motion  only, 
and  is  supported  on  four  legs  or  vertical  shafts,  one  at  each  corner,  which 
are  connected  to  lever  arms  mounted  on  shafts  with  other  arms  for  counter 
weights  and  lifting.  The  torque  of  the  counter  weight  just  about  equals 
that  produced  by  the  table.  The  material  is  then  raised  and  lowered  by 
a  reversing  electrical  motor,  which  is  provided  with  a  magnetic  brake  for 
automatically  stopping  the  tables  at  the  correct  levels.  By  means  of  a 
long  lever  arm,  the  two  tables  are  connected  and  are  raised  and  lowered 
in  unison.  The  one  on  the  approach  side  of  the  mill  is  provided  with 
stationary  vertical  skid  bars,  or  transfer  fingers,  between  the  table  rolls, 
which  are  so  arranged  that  the  act  of  lowering  the  table  edges  and  trans- 
fers the  piece  to  the  next  bottom  pass.  The  bloom  from  the  forty-eight  inch 
mill  is  edged  to  enter  the  forty  inch  mill  by  means  of  single  collar  rolls. 
Shears  of  the  side  cutting  type,  electrically  operated,  are  provided  fifty- 
six  feet  from  the  roll  table  for  cutting  the  piece  into  blooms  of  the  desired 
length  after  the  required  discard  has  been  sheared  off. 


THREE-HIGH  BLOOMING  MILL  381 

Roll  Design  for  Three=High  Bloomers :  The  peculiarities,  previously 
pointed  out,  in  the  size,  the  arrangement,  and  the  grooves  of  the  rolls  for 
this  mill  are  common  to  three-high  bloomers,  and  represent  the  effort  on 
the  part  of  the  designers  of  the  rolls  to  overcome  certain  difficulties  inherent 
in  this  type  of  mill.  First,  in  order  to  avoid  weakening  the  rolls  by  increas- 
ing their  length  unduly,  only  a  small  number  of  passes,  usually  nine,  are 
available.  Second,  except  at  rail  mills,  which  are  the  only  mills  in  exist- 
ence where  any  preliminary  reduction  of  the  ingots  is  made,  this  limited 
number  of  passes  means  that  very  heavy  drafts  must  be  taken  in  order  to 
reduce  the  ingot  to  the  more  common  bloom  sizes.  Third,  in  order  to  get 
in  the  greatest  possible  number  of  passes  on  a  set  of  rolls,  the  passes  must 
be  placed  one  above  the  other,  hence  a  groove  in  the  middle  roll  must 
serve  for  both  an  upper  and  lower  pass.  Fourth,  the  peripheral  speed  at 
the  base  of  the  grooves  in  any  two  rolls  forming  a  pass  must  be  equal,  or 
nearly  so,  if  the  piece  is  to  roll  without  curling  when  coming  out  of  the 
pass.  *  However,  the  pass  diameter  of  the  top  roll  for  any  pass  may  be  a 
little  larger  than  the  bottom,  for  then  the  piece  will  be  held  down  but 
may  be  prevented  from  curling  down  by  the  guards  on  the  mill.  On  forty 
inch  mills  this  difference  is  about  one-fourth  of  an  inch  and  is  determined 
by  practice. 

An  Example  of  Roll  Design  for  Three-High  Blooming  Mill  will 
perhaps  be  the  best  answer  to  the  question  as  to  how  all  these  conditions 
are  met.  A  specific  problem  and  a  method  of  solving  it  are  hereby  given: 

Given:     Ingot  21"  x  23",  Bloom  9"  x  10",  number  passes  9,  Size  of  Mill  42". 
Required:     To  design  rolls  for  the  mill. 

Solution: — First:  The  draught  on  each  pass  is  found.  In  finding 
the  draughts  it  is  to  be  borne  in  mind  that  the  draughts  on  the  bottom  passes , 
being  edging  passes,  should  be  heavier  than  on  the  top  passes;  that  it  is  well 
'to  take  the  heaviest  draughts  on  the  first  bottom  passes  while  the  steel 
is  hot  and  the  piece  is  short,  which  will  prevent  great  strains  on  the  engine 
as  the  momentum  of  the  fly  wheel  will  carry  across  a  short  length;  that 
the  top  passes  are  best  made  of  equal  draughts;  and  that  little  work  can 
be  done  on  the  finishing  pass.  The  reduction  in  size  of  the  ingot  to  the 
bloom  calls  for  twelve  inches  on  one  side  and  thirteen  inches  on  the  other, 
or  a  total  of  twenty-five  inches.  Since  the  reductions  on  the  bottom  passes 
are  to  be  greater  than  those  on  the  top,  let  this  total  draught  be  appor- 
tioned to  give  ten  inches  on  top  passes  and  fifteen  inches  on  bottom  ones. 
The  draught  on  each  top  pass  will  then  be  two  and  one-half  inches.  The 
draught  on  the  bottom  passes  may  be  arbitrarily  apportioned,  but  to  accord 
with  the  cautions  stated  above,  they  are  determined  by  trial,  and  to  give 
the  total  reduction  of  fifteen  inches  they  should,  apparently,  be  apportioned 
as  follows:  No.  1  pass,  3^";  No.  3  pass,  3%";  No.  5  pass,  3M";  No.  7  pass, 


THE  ROLLING  OF  STEEL 


3/4" >  No.  9  pass,  1".     The  complete  plan  for  working  the  ingot  down  to 

size  would  then  be  as  follows: 

Size  of  the  original  ingot,  21"  x  23". 

No.  1  Pass,  bottom,  draught  3}/£";  size  of  bloom  produced,  21"  x  193^". 

No.  2      «      top  «        2Y2"\    "      "       "  "          21"xl7". 

Piece  edged. 

No.  3  Pass,  bottom,  draught  3%";  size  of  bloom  produced,  17%"  x  17". 
No.  4     «     top,  "        2^";    «     «       «  "          14%"xl7". 

Piece  edged. 

No.  5  Pass,  bottom  draught  3^";  size  of  bloom  produced,  14%"  x  13%". 
No.  6      «     top,  "        2^";    «     "       «  "  14%"xll". 

Piece  edged. 

No.  7  Pass,  bottom,  draught  3%"',  size  of  bloom  produced,  11^"  x  11". 
No.  8     «     top,  «       ,2^";    «     "       "  "  9"     x  11". 

Piece  edged. 
No.  9  Pass,  bottom,  draught  1";     size  of  bloom  produced,    9"      x  10". 

Second:    The  most  suitable  pitches  for  the  rolls  are  determined. 

By  pitch  is  meant  the  distance  from  center  to  center  of  a  pair  of  rolls  with- 
out clearance,  or  the  distance  between  any  two  of  the  pitch  lines.  These 
are  based  on  the  size  of  the  mill;  the  average  pitch  for  the  top  and  bottom 
sets  of  passes  are  equal  to  its  size,  and  should  be  such,  for  reasons  already 
noted,  that  each  roll  will  be  approximately  one-fourth  inch  less  in  diameter 
than  the  one  above  it.  The  pitch  is,  therefore,  determined  by  trial  as 
follows:  In  this  case  the  proper  figures  appear  to  be 

"  from  center  to  center  of  top  and  middle  roll. 

«        «        «       «  bottom  and  middle  roll. 
(84"-H2=42"=the  size  of  the  mill.) 

From  these  figures  the  working  diameter  of  the  passes  are  found  as 
follows: 

43>i"  pitch  of  bottom  and  middle  roll. 

19^"  height  of  first  pass,  (See  size  of  bloom  for  No.  1  pass.) 
2 1  23%"  pass  diameter  of  first  pass. 

11%" — ^"=11%"  first  pass  radius  of  bottom  roll,  or  first  pass  working 
diameter=23^". 

M"=llJir/  first  pass  radius  of  middle  roll,  or  first  pass  working 
diameter=23M". 

17"  (size  of  No.  2  pass)=28K". 

(pitch  of  top  and  middle  roll)— 28%"=12",  first  pass  radius  of 
the  top  roll;  or  first  pass  working  diameter  of  top  roll=2//xl2"=24. 
As  this  diameter  is  a  little  larger  (J£")  than  that  for  the  middle  roll, 
the  pitches  assigned  above  are  assumed  to  be  the  proper  ones. 


THREE-HIGH  BLOOMING  MILL 


383 


384  THE  ROLLING  OF  STEEL 

Third:  The  size  of  each  roll  is  determined.  As  a  preliminary  step 
to  finding  the  size  of  the  rolls,  the  diameters  of  the  middle  and  bottom 
rolls  may  be  assumed  to  be  the  same  as  their  pitches,  forty-three  and  one- 
eighth  inches.  The  pitch  size  for  the  middle  and  top  roll  is  forty  and 
seven-eighths  inches,  and  if  from  twice  this  pitch  the  diameter  of  the 
middle  roll  is  subtracted,  the  pitch  diameter  of  the  top  roll  is  the  result, 
which  in  this  case  would  be  thirty-five  and  five-eighths  inches.  If,  now, 
the  diameter  of  the  working  pass  in  the  middle  roll  is  subtracted  from  this 
diameter  of  the  roll,  the  result  is  twice  the  depth  of  the  groove. 

43^"— 23%"=19^".  19%"-^2=9%"  depth  of  first  groove  in  middle  roll. 
Similarly,  38%"— 24=14%".  U%"-+-2=7%",  depth  of  groove  for  the  top 

roll.  The  sum  of  these  two  quantities  is  seventeen  inches  which  checks 
with  the  size  of  second  pass.  But  more  of  the  piece  lies  in  the  middle 
than  in  the  top  roll,  so  in  order  to  get  the  same  height  of  collar,  eight  and 
one-half  inches  in  each  roll,  it  is  necessary  to  increase  the  radius  of  the 
top  roll  and  decrease  the  radius  of  the  middle  by  nineteen-sixteenths  inches, 
making  their  respective  diameters  forty-one  inches  and  forty  and  three- 
fourths  inches.  The  diameter  of  the  bottom  roll  would  then  be  forty-five 
and  one-half  inches  (2  x  43^" — 40%").  In  order  to  get  the  proper  clearance 
between  the  rolls,  which  is  assumed  to  be  one  inch,  these  diameters  are 
further  reduced  to  forty  inches,  the  diameter  of  top  roll;  thirty-nine  and 
three-fourths  inches,  the  diameter  of  middle  roll;  and  forty-four  and  one- 
half  inches,  the  diameter  of  bottom  roll.  These  diameters  give  a  much 
deeper  groove  in  the  bottom  roll  than  in  the  middle,  which  can  be  over 
come  by  cutting  down  the  collars  on  the  bottom  roll,  which  has  the  effect 
merely  of  increasing  the  clearance.  So  to  balance  up  the  depths  of  these 
grooves  a  clearance  of  two  inches  is  allowed  between  these  rolls,  making 
the  final  diameter  of  the  bottom  roll  forty-two  and  one-half  inches.  The 
finding  of  the  depth  of  the  remaining  grooves  is  a  simple  manner.  Thus, 
for  example,  No.  4  pass  is  14%"  x  17".  From  the  depth  of  the  pass,  fourteen 
and  three-fourths  inches,  the  clearance  of  one  inch  is  subtracted,  leaving 
thirteen  and  three-fourths  inches.  This  depth  is  equally  divided  between 
the  top  and  middle  rolls,  making  six  and  seven-eights  inches  in  each.  It 
follows  that  the  groove  in  the  middle  roll  for  No.  3  pass  must  be  the  same. 
As  the  depth  of  this  pass  is  seventeen  and  one-fourth  inches,  the  groove  in 
the  bottom  roll  must  be  eight  and  three-eighths  inches,  (17%" — 6%" — 
2"—8%").  The  accompanying  sketch  shows  a  set  of  rolls  designed 
according  to  the  explanation  given  above.  To  take  care  of  variations  due 
to  wear  in  the  rolls  and  permit  of  their  being  dressed,  thus  increasing  their 
life,  the  entire  set  is  made  a  little  over-size  in  diameter  of  body,  usually 
about  three-fourth  of  an  inch.  They  are  discarded  when  they  have  been 
dressed  down  to  the  same  amount  undersize. 


V 

SLABS  385 


SECTION   V. 

THE   ROLLING   OF   SLABS. 

The  Rolling  of  the  Slab  is  the  first  step  in  the  rolling  of  plates,  just 
as  the  bloom  marks  the  first  step  in  rolling  the  many  shapes.  Attention 
has  already  been  called  to  the  rolling  of  slabs  on. the  reversing  blooming 
mill.  For  rolling  narrow  slabs,  the  blooming  mill  meets  all  the  require- 
ments, but  the  width  of  the  slabs  rolled  on  these  mills  is  limited  to  the 
maximum  spread  of  the  rolls  on  account  of  the  necessity  of  edging  the  piece 
near  the  last  passes.  In  America,  therefore,  slabs  are  rolled  for  the  most 
part  on  the  universal  mill  principle,  in  which  the  width  of  the  slab  is  partly 
controlled  by  means  of  vertical  rolls  which  work  on  the  edges  of  the  slab. 
The  slabbing  mills  are  not  true  universal  mills,  however,  but  double  or 
duplex  mills,  made  up  of  one  stand  of  rolls,  similar  to  the  blooming  mills 
but  with  plain  instead  of  collared  rolls,  and  one  stand  of  vertical  rolls  near 
to  and  in  front  of  the  horizontal  rolls.  Each  mill  is  driven  independently, 
and  both  are  reversing.  By  such  an  arrangement  larger  ingots  may  be 
rolled  than  would  be  possible  on  the  reversing  blooming  mill.  Since  the 
piece  is  not  edged  under  the  horizontal  rolls,  ingots  varying  in  thickness 
and  slabs  of  great  width  may  be  handled.  The  following  sizes  as  to  thick- 
ness and  widths  of  ingots  are  rolled  by  the  thirty-two  inch  mill  to  be 
described  later,  23%"  x  23%";  26"  x  40",  26"  x  45",  26"  x  48";  26"  x  53" 
and  27"  x  57".  The  thickness  of  the  ingot  is  limited  by  the  maximum 
height  to  which  the  top  horizontal  roll  may  be  lifted,  while  the  width  is 
controlled  by  the  spread  of  the  vertical  rolls.  In  preparation  for  the  rolling, 
the  ingots  are  treated  in  soaking  pits  in  the  same  manner  as  that  already 
described  for  the  blooming  mills. 

The  Thirty-two  Inch  Mill  at  Homestead  as  an  Example  of  a 
Slabbing  Mill:  This  mill  is  an  old  mill  and  was  originally  designed  to 
roll  armor  plate.  It  is,  therefore,  somewhat  larger  and  stronger  than  some 
more  recently  constructed  slabbing  mills.  However,  the  main  features  and 
the  principles  of  both  the  construction  and  operation  are  the  same  on  this 
mill  as  those  of  other  slabbing  mills.  As  noted  above,  the  mill  consists  of 
two  separately  driven  stands  of  rolls — the  horizontal  and  vertical  stands, — 
which  are  best  described  separately. 

The  Horizontal  Mill :  The  'rolls  on  this  stand  are  four  in  number, 
arranged  one  above  the  other  on  the  plan  of  a  four-high  mill.  Only  the 
two  intermediate  rolls  actually  come  in  contact  with  the  ingot,  however, 
the  topmost  and  bottommost  rolls  being  used  as  reinforcing  or  stiffening 
rolls  to  the  two  intermediate  ones.  All  these  rolls  are  nine  feet  two  inches 
long  in  the  body,  but  the  re-enforcing  rolls  are  thirty-two  inches  in  diameter, 
while  the  intermediate  ones  are  twenty-six  inches  in  diameter.  This 
arrangement  permits  a  more  rapid  reduction  of  the  ingot  and  with  less 


386  THE  ROLLING  OF  STEEL 

power  than  would  be  possible  with  only  two  rolls,  which  would  have  to  be 
of  large  diameters  to  give  the  great  strength  required.  The  smaller  roll, 
exposing  little  surface  to  the  steel,  sinks  into  the  metal  with  less  pressure 
and  is  turned  with  less  power.  The  four  rolls  are  held  in  place  by  a  cast 
steel  housing.  The  necks  of  the  bottom  re-enforcing  roll  rest  on  bearings 
fitted  into  the  bottom  of  the  housing;  this  roll  then  supports  the  lower 
intermediate  roll,  the  contact  being  made  the  entire  length  of  their  bodies. 
Lateral  displacement  of  this  lower  intermediate  roll  is  prevented  by 
babbitted  side  bearing  boxes  at  either  end.  The  two  upper  rolls  are  held 
in  two  steel  frames,  one  at  each  end,  each  of  which  is  fitted  with  a  brass 
top  bearing  for  the  re-enforcing  roll  and  a  box  fitted  with  bottom  and  side 
bearings  for  the  top  intermediate  roll.  As  these  frames  move  up  and  down 
with  the  adjustment  of  the  top  rolls,  guide  bars  bolted  to  the  outer  edges 
of  the  windows  are  provided  to  hold  them  in  place,  while  liners  inserted 
between  the  frames  and  the  sides  of  the  windows  prevent  the  wearing  away 
of  the  housings.  The  ends  of  two  plunger  rods  rest  against  the  bottom  of 
this  frame  while  the  rods  extend  to  hydraulic  cylinders  which,  located 
beneath  the  mill  and  acting  under  a  pressure  of  600  Ibs.  per  sq.  in.,  are 
used  for  raising  the  top  rolls.  The  rolls  are  lowered  by  means  of  screws 
similar  to  those  in  the  blooming  mill,  but  in  this  case  the  power  for  the 
screw  down  is  obtained  from  a  60  h.  p.  motor  mounted  on  a  platform  a 
little  above  the  top  of  the  housing.  The  screws  rest  on  breaker  blocks 
which  serve  as  a  safety  to  prevent  the  breaking  of  the  rolls.  The  maximum 
lift  of  the  mill  is  nearly  forty  inches.  For  indicating  the  distance  between 
the  rolls  a  gauge  pole  and  disc  are  provided.  The  disc  is  mounted  on  top 
of  one  of  the  screws  with  the  marking  pole  adjacent  to  it.  The  circum- 
ference of  the  disc  is  divided  into  100  equal  parts,  while  the  pole  is  divided 
into  spaces  of  one  inch  each.  These  divisions  on  pole  and  disc  are  plainly 
marked  and  permit  the  opening  of  the  mill  to  be  read  to  within  1-100  of 
an  inch.  The  Drive  for  the  horizontal  mill  is  connected  to  the  intermediate 
rolls,  the  re-enforcing  rolls  being  friction  driven.  The  motive  power  is 
furnished  by  a  40"  x  54"  horizontal  reversing  engine,  which  is  indirectly 
connected  to  the  leading  or  driving  spindle  of  the  mill. 

The  Vertical  Mill  is  located  about  ten  feet  in  front  of  the  horizontal 
mill,  measuring  from  center  to  center  of  the  rolls.  Like  the  horizontal 
mill  the  vertical  mill  has  four  rolls,  two  of  which  are  re-enforcing;  but  these 
rolls  are  much  smaller  than  the  horizontal  ones,  being  only  eighteen  inches 
in  diameter  and  about  forty-four  inches  in  length,  or  a  little  longer  than  the 
lift  of  the  horizontal  mill.  The  rolls  are  supported  vertically  in  the  housings 
by  means  of  bearing  boxes  at  both  the  tops  and  bottoms.  These  boxes  are 
held  in  place  by  heavy  rest  bars  which  extend  across  the  mill  at  top  and 
bottom  and  from  housing  to  housing,  between  the  windows  of  which  they 
are  securely  fastened.  For  adjusting  the  spread  of  the  rolls  inwardly  two 
screws,  acting  horizontally  through  the  sides  of  the  housings  instead  of 


THE  SLABBING  MILL  387 

through  the  top  as  for  horizontal  rolls,  are  provided.  They  bear  on  a 
frame  that  extends  from  the  top  to  the  bottom  bearings,  and  are  operated 
by  a  50  h.  p.  motor  through  a  system  of  gears.  For  spreading  the  rolls  apart 
hydraulic  jacks  are  used.  In  operating  the  mill,  all  four  of  the  rolls  are 
driven.  Starting  with  the  engine,  the  connections  are  made  as  follows: 
The  engine,  a  36"  x  57"  horizontal  reversing  steam  engine,  is  mounted  upon 
a  concrete  foundation  a  little  above  the  level  of  the  bottom  of  the  housings 
and  on  the  opposite  side  of  the  mill  from  that  on  which  the  engine  for  the 
horizontal  rolls  is  placed.  The  power  is  indirectly  transmitted  through 
two  gears,  one  above  the  other,  to  the  driving  shaft,  which  extends  from 
the  upper  gear  to  the  farther  side  of  the  mill.  To  this  shaft,  the  two  outside 
rolls  are  connected  by  means  of  bevelled  crown  and  sleeve  gears,  while 
a  second  set  of  gears  connecting  the  inside  and  outside  rolls  in  pairs  furnish 
the  means  by  which  the  driving  of  the  inside  rolls  is  effected.  The  hori- 
zontal rolls  are  run  at  full  speed,  while  the  speed  of  the  vertical  rolls  is 
controlled  by  the  engineer  to  suit  that  of  the  horizontal  mill.  While  the 
maximum  spread  of  the  vertical  rolls  is  about  sixty-five  inches,  the  widest 
slabs  rolled  are  only  fifty-four  inches  wide,  because  this  is  the  greatest 
width  the  mill  shears  are  built  to  cut.  The  excessive  length  of  the  hori- 
zontal rolls  (one  hundred  ten  inches  in  the  body,  as  previously  given)  is 
explained  by  the  fact  that  this  mill  was  formerly  used  for  rolling 
armor  plate. 

Precautions  to  be  Observed  in  Rolling  Slabs:  The  essential  part  of 
the  rolling  is  the  determination  of  the  draughts  to  be  taken  on  each  pass 
through  the  mill.  This  determination  is  made  by  the  roller  from  the 
dimensions  of  the  ingot  to  be  rolled,  the  slabs  desired  as  given  on  the  rolling 
order  sheets,  the  temperature  of  the  ingot  as  it  comes  to  the  rolls  and  the 
steam  pressure  available  for  the  engines.  The  temperature  controls  the 
draught  in  that  the  hotter  the  steel  the  less  the  pull  on  the  mill  and  the 
greater  is  the  possible  draught.  Uniform  temperature  throughout  the 
ingot  is  also  necessary  to  insure  good  rolling,  as  steel  hotter  on  one  side 
than  the  other  causes  curling  of  the  slabs,  due  to  the  fact  that  steel  always 
curls  towards  the  cold  side,  because  the  elongation  is  less  on  that  side. 
To  assist  in  rolling,  ingots  are  fed  to  the  rolls  with  the  hot  side  up  and 
the  small  end  first,  thus  affording  a  better  grip  by  the  rolls  and  preventing 
or  lessening  the  tendency  for  the  slab  to  curl  up  when  leaving  the  mill  as 
they  do  when  the  cold  side  is  turned  up.  Slabs  are  often  hotter  on  one 
side  than  the  other,  which  condition  also  causes  curling,  due  to  the  greater 
spreading  or  flowing  of  the  steel  on  the  hot  side.  Indirectly,  the  chemical 
composition  of  the  ingot  regulates  the  possible  draught;  high  carbon  steel, 
for  example,  cannot  be  heated  as  hot  as  common  plate  steel,  hence  longer 
time  and  smaller  draughts  must  be  taken  in  the  rolling.  The  total  vertical 
draught,  which  in  all  cases,  except  27"  x  57"  ingots,  amounts  to  about  one 
inch,  is  taken  during  the  first  few  passes.  From  then  on,  the  vertical  rolls 


388  THE  POLLING  OF  STEEL 


are  kept  in  contact  with  the  steel  at  a  pressure  only  sufficient  to  prevent 
tearing  of  the  edges  which  results  when  no  pressure  is  applied  on  the  sides 
of  the  slab.  With  small  ingots  tearing  of  the  steel  is  also  caused  when  the 
ingots  are  not  hot  enough  for  good  rolling  but  still  capable  of  being  passed 
through  the  rolls.  In  the  case  of  large  ingots  that  are  cold,  there  is  little 
danger  of  injuring  them,  because  there  is  not  sufficient  power  to  roll  them, 
as  in  the  case  of  smaller  ingots.  Correct  lining  of  the  rolls  is  necessary  to 
make  good  slabs,  since  if  the  rolls  are  crossed  or  are  higher  on  one  end 
than  on  the  other  the  slabs  curl.  At  the  thirty-two  inch  mill  the  driving 
end  of  the  rolls  is  always  kept  slightly  higher  than  the  other  end  to  allow 
for  the  more  rapid  wearing  of  the  bearings  due  to  the  extra  weight  on 
that  side  of  the  mill.  Above  y%"  the  slabs  will  curl  in  passing  through 
the  mill.  The  maximum  draught,  i.  e.,  reduction  in  sectional  area,  that 
can  be  taken  by  the  horizontal  rolls  with  the  steel  at  a  good  rolling 
temperature  is  approximately  thirty  square  inches  on  the  entering  pass  and 
forty  square  inches  on  the  return  pass.  The  difference  in  reduction  possible 
on  the  entering  and  return  passes  is  due  to  the  fact  that,  on  the  return  pass, 
the  vertical  rolls  aid  in  pulling  the  slab  through  the  mill,  while  they  cannot 
effect  any  power  by  pushing  the  slab  when  going  in  the  opposite  direction. 
For  the  entering  pass  thirty  divided  by  the  ingot  width  gives  the  approxi- 
mate draught,  or  bite,  and  forty  divided  by  the  ingot  width,  the  return 
pass  bite.  The  last  pass  taken  is  entering,  and  is  a  pass  in  which  very  little 
pressure  is  used  in  order  to  straighten  the  plate,  roll  down  the  top  ends,  and 
remove  the  convex  surf  ace  due  to  the  spring  from  the  rolls. 

Removal  of  Scale:  During  the  rolling  of  an  ingot  the  scale  must  be 
removed  from  the  surface  to  prevent  the  slab,  and  resulting  plates,  from 
being  pitted.  The  process  employed  in  removing  the  scale  depends  upon  the 
kind  of  steel  being  rolled.  For  removing  scale  on  low  carbon  steel  salt  and 
water,  the  latter  being  sprayed  on  the  slab  at  high  pressure  and  the  former 
thrown  on  with  scoops,  are  very  effective.  In  case  of  high  carbon  steel  the 
scale  sticks  more  firmly  to  the  slab,  and  burlap  sacks  are  used,  as  neces- 
sary, in  addition  to  salt  and  water.  When  nickel  steel  is  rolled,  coal  is 
used  in  place  of  salt,  and  burlap  is  also  thrown  under  the  rolls.  Brush  or 
green  twigs  are  often  employed  to  serve  the  same  purpose  as  burlap.  The 
actions  of  all  these  substances  are  somewhat  similar.  In  each  case  the 
substance  is  drawn  under  the  rolls,  which  tend  to  bring  it  rapidly  into 
close  contact  with  the  hot  metal.  The  material  thus  caught  by  the  rolls 
is  gassified  by  the  heat,  and,  in  an  effort  to  escape,  the  gases  get  beneath 
the  scale  and  carry  it  off  with  them.  Coal  and  burlap,  being  less  volatile 
than  salt  or  water,  are  carried  a  little  farther  beneath  the  rolls  and  give 
a  more  violent  action.  Nickel  scale  is  the  most  difficult  of  all  to  remove, 
and  if  the  first  scale  is  melted  off  in  the  soaking  pits  and  a  second  formed, 
it  is  almost  impossible  to  clean  it  off.  All  nickel  bearing  slabs  are  cleaned 
first  on  one  side,  then  turned  over  by  cranes  and  cleaned  on  the  other  side. 


SLABS  389 


Shearing  Slabs  at  the  Thirty=two  Inch  Mill:  From  the  rolls  the 
slabs  pass  by  means  of  motor  driven  roll  tables  to  a  hydraulic  shear.  Two 
plungers  are  used  to  operate  the  knife,  a  small  one  on  top  for  lifting  the 
blade  and  a  large  one  on  the  bottom  for  pulling  the  knife  down  against  the 
steel,  thus  effecting  the  cutting.  Two  Wilson  and  Snyder  pumps,  an  accumu- 
lator and  steam  intensifiers  comprise  the  operating  equipment.  The  slabs 
are  cut  to  length  by  means  of  a  scale  of  marks  placed  on  a  steel  slab  in  front 
and  to  one  side  of  the  shears.  Graduations  on  this  marker  indicate  the 
distance  from  the  shear-blade,  so  by  running  the  slab  out  to  any  certain 
mark  the  length  of  slab  is  indicated  by  the  graduation.  The  roll  table 
approaching  the  shear-blade  is  also  graduated  in  inches  of  distance  from 
the  blade.  By  fixing  the  eye  on  any  spot  or  mark  on  the  slab  at  any  distance 
from  the  knife  as  shown  by  position  on  scale  and  watching  this  mark  until 
it  is  moved  beneath  the  knife,  the  length  of  slab  can  be  obtained.  The 
size  (total  weight)  of  the  slab  is  determined  by  the  dimensions  and  gauge 
of  the  plate  into  which  it  is  to  be  rolled.  Since  the  width  of  the  ingot 
limits  the  width  of  the  slab,  planning  the  size  of  the  slab  starts  with  the 
selection  of  an  ingot  of  the  proper  size.  Next,  the  thickness  of  the  slab 
must  be  determined,  and  then  the  length.  It  is  evident  that  very  careful 
work  is  necessary  in  making  up  the  mill  schedule,  if  the  steel  is  to  be  rolled 
to  best  advantage.  All  this  planning  is  done  in  the  mill  office,  and  the 
shearman  is  generally  given  the  lengths  into  which  the  slabs  are  to  be  cut, 
though  occasionally  he  may  be  ordered  to  cut  to  best  advantage.  The  first 
cut  made  on  the  slab  is  to  remove  the  piped  end.  After  the  discard  is 
sheared  off,  a  few  slabs  are  cut,  when  the  piece  is  turned  around  with  a 
manipulator,  the  bottom  crops  taken  off,  and  the  remainder  cut  into  slabs. 
From  the  rolling  sheets,  the  shearman  gets  the  length  of  slabs  ordered  and 
the  amount  of  discard  that  is  to  be  taken  before  slabs  can  be  cut.  Cuts  are 
usually  made  up  to  the  center  of  the  slab  before  turning  it  around.  By 
turning  the  slab  the  shearman  can  tell  how  much  steel  will  remain  after 
taking  off  the  bottom  crop  and  better  decide  as  to  how  he  shall  cut  the 
remainder.  Slabs  are  cut  as  ordered  if  possible,  and  if  a  piece  is  left  over 
that  is  too  large,  or  heavy,  for  any  slab  ordered,  it  is  marked  as  an  "odd" 
cut.  For  example,  a  5000  pound  slab  is  ordered,  and,  after  the  first  slabs 
have  been  cut,  the  remaining  piece  is  7000  pounds,  or  2000  pounds  over  the 
weight  desired.  Were  this  7000  pounds  to  be  used  on  a  slab  calling  for  only 
5000  pounds,  2000  pounds  would  be  scrapped  in  the  plate  mill.  This  system 
is  too  expensive,  so  the  slab  is  marked  as  an  odd  cut  and  placed  on  some 
other  order.  The  limits  as  to  width  and  thickness  of  slab  that  may  be 
sheared  on  this  shear  are  fifty-four  inches  and  twenty  inches,  respectively. 
The  percentage  of  discard  varies  from  about  15%  on  plain  steel  to  35%  on 
some  special  orders;  the  larger  portion  of  the  discard  is  taken  from  the  top 
of  the  ingot  on  account  of  the  segregation  and  piping  being  mostly  confined 
to  this  section.  All  discarded  steel  is  placed  in  open  hearth  charging 
buggies  and  shipped  to  the  open  hearth,  note  being  taken  of  the  special 


390  THE  ROLLING  OF  STEEL 

alloy  steel  scrap,  which  is  kept  separate  from  the  plain  steel  scrap.  As  the 
slabs  are  cut,  they  are  stamped  with  a  serial  number,  beginning  with  one 
from  the  first  of  the  year.  A  recorder  takes  down  the  slabs  made,  size, 
number,  cut,  etc.,  and  enters  it  on  the  product  side  of  the  rolling  order 
sheet.  The  weight  of  ingot,  weight  of  slabs  made,  and  weight  of  scrap  is 
noted,  and  the  information  sent  to  the  product  department.  From  this 
data  the  practice  of  the  mill  is  figured. 


BILLETS  AND  OTHER  PRODUCTS  391 


CHAPTER  VI. 

THE  ROLLING  OF  BILLETS  AND  OTHER  SEMI-FINISHED 
PRODUCTS. 

SECTION   I. 

THE  THREE-HIGH  BILLET  MILL. 

General  Features  of  Rolling  Billets:  A  large  percentage  (over  50%) 
of  the  steel  produced  is  rolled  into  material  of  very  small  section.  In  order 
to  finish  their  product  in  one  heat,  the  mills  rolling  such  sections  must 
start  with  small  billets.  While  many  blooming  mills  of  the  reversing  type 
are  able  to  roll  billets  as  small  as  4"  x  4"  or  less,  which  is  a  size  much  too 
large  for  the  majority  of  the  smaller  mills,  the  inadvisability  of  employing 
these  large  mills  for  rolling  billets  is  at  once  evident,  and  accounts  for  the 
existence  of  the  billet  mill.  In  order  to  reduce  the  cost  of  the  billet,  the 
billet  mill  will  be  placed  just  after  the  blooming  mill  so  as  to  effect  the 
reduction  from  ingot  to  billet  on  the  original  heat  of  the  former.  As  to 
the  kinds  of  mills  used  for  rolling  billets,  almost  any  mill  of  medium  size 
may  be  adapted  to  the  work.  Since  the  section  is  a  very  simple  one  and 
so  little  in  the  way  of  accuracy  as  to  form  of  section  or  of  finish  is  necessary, 
about  the  only  requirements  of  the  billet  mill  is  that  it  be  heavy  enough 
to  handle  fairly  large  blooms  and  speedy  enough  to  reduce  the  piece  to  the 
desired  size  before  it  becomes  too  cold.  For  the  larger  sized  billets,  a 
single  stand  of  three-high  rolls  placed  after  the  bloomer  serves  very  well, 
but  for  small  billets  that  are  not  intended  for  certain  special  purposes,  like 
forgings,  for  example,  the  continuous  mill  is  the  best  mill  for  the  purpose. 

Example  of  Three-high  Billet  Mill— The  Twenty-eight  Inch  Mill 
at  Duquesne:  As  an  example  of  the  former  type  of  mill  the  twenty-eight  inch 
mill  at  Duquesne  will  be  described,  because  every  device  is  employed  to 
increase  the  out-put,  and  it  also  is  an  example  of  how  the  mills  are  compelled 
to  adapt  themselves  to  change  in  conditions.  This  mill  was  originally 
designed  as  a  rougher  for  a  rail  mill,  but  was  rebuilt  in  1907.  The  mill  is 
fed  by  a  thirty-eight  inch  two-high  bloomer  which  reduces  an  18}/£"  x  20^" 
ingot  to  a  7J4"  x  8%"  bloom.  The  twenty-eight  inch  mill  at  Clairton 
placed  after  the  forty-inch  bloomer  is  very  similar  to  the  Duquesne  twenty- 
eight-inch  mill. 

Engine:  The  mill  is  direct  driven  by  a  Cooper  Corlise  tandem 
compound  horizontal  condensing  engine,  44"  x  74"  x  54",  designed  to 
develop  2500  h.  p.  at  75  r.  p.  m.  and  25%  cut-off  and  to  run  at  80  r.  p.  m. 


392  THE  ROLLING  OF  STEEL 

at  120  to  125  pounds  steam  pressure.  The  engine  is  capable  of  developing 
4500  to  5000  h.  p.  The  ordinary  speed  is  about  62  r.  p.  m.  and  the  normal 
load  about  1200  h.  p.,  the  maximum  being  about  3500  i.  h.  p.  per  pass.  The 
steam  consumption  is  about  300  pounds  per  ton  of  steel  rolled.  The  exhaust 
from  the  low  pressure  cylinder  is  taken  to  a  central  condensing  plant 
near  the  engine  house;  this  plant  is  of  the  Weiss  barometric  type  and 
is  equipped  with  the  following  apparatus:  One  20"  x  42"  x  24"  air  pump 
and  two  Wilson-Snyder  18"  x  30"  x  26"  x  36"  8,000,000  gallon  duplex  com- 
pound-plunger water  pumps.  The  engine  is  controlled  in  the  engine  house 
by  a  sixteen  inch  throttle  valve  and  may  be  shut  down  quickly  in  an 
emergency  by  a  sixteen  inch  quick-closing  valve  just  above  the  throttle. 

Drive:  The  crank  shaft  is  connected  through  a  flexible  coupling  to 
the  spindle  shaft.  The  cast  steel  coupling,  five  feet  six  inches  in  diameter 
is  keyed  tight  to  the  Crank  shaft  of  the  engine  with  a  bronze  half  thrust 
collar  over  the  half  coupling;  a  .80%  carbon  steel  wearing  plate  is  screwed 
to  the  outboard  bearing  support  of  the  engine  and  separates  the  collar  from 
it.  Eight  two  and  three-fourths  inch  bolts  hold  a  second  half  coupling  to 
the  first  one.  The  former  fits  over  a  cast  steel  hub  keyed  to  the  engine 
end  of  a  cast  steel  spindle  shaft,  twenty  inches  in  diameter.  The  engine 
end  of  the  spindle  shaft  is  slightly  curved  to  promote  flexibility.  The  spindle 
shaft  is  seventeen  feet  eight  and  one-half  inches  long  and  twenty  inches  in 
diameter,  and  three  feet  seven  and  one-half  inches  from  its  end  is  the  center 
line  of  a  20"  x  48"  ring  oil  bearing,  which  supports  the  mill  end  of  the  spindle 
shaft.  The  oil  bearing  is  held  in  a  cast  iron  yoke  and  base,  mounted  on  a 
cast  iron  hot  plate.  The  bearing  is  lined  with  babbitt  and  is  provided  with 
small  oil  grooves  for  lubricating.  A  tight  crab,  four  feet  in  diameter,  of 
cast  steel  is  keyed  to  the  mill  end  of  the  spindle  shaft;  two  and  one-half 
inch  bolts  hold  a  four  foot  cast  steel  loose  crab  to  the  tight  crab.  A 
cast  steel  compound  coupling  fits  over  the  mill  end  of  the  loose  crab  and 
the  adjacent  wobbler  of  the  leading  spindle.  The  cast  steel  leading  spindle 
is  three  feet  ten  and  one-half  inches  long  and  sixteen  inches  in  diameter. 
A  plain  cast  steel  coupling  box  joins  the  leading  spindle  to  the  middle  of 
the  mill,  fitting  over  the  adjacent  wobblers  of  each. 

Pinions  and  Their  Housings:  The  pinion  housings  for  the  twenty- 
eight  inch  mill  are  steel  castings  bolted  to  the  mill  shoes;  the  housing 
windows  are  seven  feet  three  inches  deep  from  the  top  to  the  sill  and  twenty- 
six  inches  wide;  one  forged  steel  liner  one  inch  thick  is  used  on  each  sill, 
and  each  window  is  faced  on  each  side  with  a  one  inch  forged  steel  liner. 
These  are  all  bolted  to  the  housings.  All  these  liners  are  forged  steel  of  .40% 
to  .50%  carbon.  The  pinions  are  steel  castings  of  the  helical  tooth  type. 
They  measure  thirty-six  inches  in  length  of  face,  and  have  thirteen  teeth 
with  a  pitch  diameter  of  twenty-nine  inches.  Their  diameter  at  the  shrouds 
is  twenty-seven  inches,  and  the  necks  taper  from  seventeen  and  three- 
eighths  to  seventeen  inches  in  diameter;  the  wobblers  are  sixteen  inches  in 


THREE-HIGH  BILLET  MILL  393 

diameter.  The  total  length  of  the  pinions  is  nine  feet  two  inches.  All  six 
pinion  bearings  are  of  the  same  pattern,  being  made  of  cast  steel  with  three- 
fourths  inch  babbitt  and  four  narrow  brass  plates  set  90°  apart.  The 
bottom  bearings  rest  flat  on  the  housing  sill  liners,  no  beveling  being 
required;  the  bearings  are  twenty-three  inches  wide,  twenty-eight  inches 
high,  and  twenty-three  and  one-half  inches  through.  The  cap  for  the 
pinion  housings  is  a  solid  steel  casting  fitting  over  both  housings;  it  has 
slots  at  its  four  corners  for  key  bolts  to  hold  down  the  pinions  tightly  beneath 
it.  Steel  eye  bolts  are  set  in  the  caps,  so  that  they  can  be  lifted  easily. 
The  housings  are  held  in  line  also  by  steel  separator  rods  on  each  side, 
top  and  bottom.  The  bottom  and  top  pinions  are  driven  by  the  middle 
pinion  and  all  three  are  connected  to  their  respective  rolls  by  cast  steel 
coupling  boxes  and  cast  steel  spindles,  unsupported. 

Housings  and  Roll  Bearings:  The  roll  housings  are  cast  steel,  closed 
at  the  top  with  a  cast  steel  cap;  the  housings  are  bolted  to  cast  iron  mill 
shoes.  The  windows  of  the  housings  are  nine  feet  two  inches  deep  and  two 
feet  nine  inches  wide.  Three  feet  one  and  one-fourth  inches  above  the  sill 
is  a  ledge  on  which  rests  the  bearing  for  the  middle  roll;  this  roll  is 
held  stationary,  the  others  being  adjusted  to  it.  Bearings  for  this  mill  are 
as  follows:  Bottom  roll:  two  steel  carrier  bearings  with  babbitt  and 
brasses.  Middle  roll:  same,  and  two  rider  bearings  with  similar  babbitt 
and  brasses.  Top  roll:  two  forged  steel  babbitted  saddles  for  carrying 
the  roll;  two  cast  steel  rider  bearings  with  babbitt  and  brasses.  The 
middle  roll  is  held  down  on  its  ledge  by  three  and  three-quarter  inch  rods, 
which  are  in  turn  held  down  by  two  five  inch  set  screws  of  one  and  three- 
quarter  inch  pitch  through  the  caps;  the  rods  press  on  the  rider  bearings 
of  the  middle  roll.  The  screws  are  adjusted  by  means  of  wrenches  which 
fit  over  nuts  at  the  top  of  the  screws.  The  carrier  bearing  of  the  bottom 
roll  rests  on  a  seat  which  is  fastened  to  a  seven-inch  screw  running  up  from 
below  the  housing  through  its  center;  this  screw  turns  in  a  charcoal  iron 
nut  shrunk  in  the  mill  housing,  and  is  regulated  by  a  gear  and  pinion  con- 
nection from  outside  the  housing.  The  gear  is  moved  by  a  vertical  rod 
with  a  slotted  wheel  in  the  top;  a  hand  lever  is  used  to  turn  this  wheel, 
and  thus  the  bottom  roll  is  raised  or  lowered.  The  top  roll  is  held  up  by 
two  counterweights  through  steelyard  rods  in  each  housing  reaching  up  to 
the  top  roll's  carrier  bearing;  the  roll  is  held  down  at  each  end  by  a  single 
seven-inch  screw  of  one  inch  pitch  reaching  through  the  cap  to  the  breaker 
block  on  the  rider  bearing.  The  screw  is  adjusted  like  a  bolt,  with  a  short 
wrench  usually  turned  by  a  crane. 

Rolls:  In  this  mill  the  top  and  bottom  rolls  are  similar  and  inter- 
changeable, while  the  middle  roll  differs  in  that  the  barrel  of  the  roll  has 
larger  diameters  than  the  bottom  roll  in  those  passes  in  which  it  acts  as 
the  top  roll,  and  smaller  diameters  where  it  acts  as  the  bottom  roll  when 
paired  with  the  top  roll.  In  passes  Nos.  1,  3,  5  and  7  the  diameters  are 


394 


THE  ROLLING  OF  STEEL 


If 


FIQ.  66.     Three-High  Billet  or  Roughing  Mill. 


THREE-HIGH  BILLET  MILL  395, 

larger  in  the  middle  roll  than  in  the  top  and  bottom  and  in  Nos.  2,  4  and  6 
they  are  smaller.  The  rolls  are  thirty  and  three-eighths  inches  in  diameter, 
eleven  feet  four  inches  long  over  all  and  six  feet  four  and  one-half  inches 
long  in  the  body;  the  passes  are  shown  in  the  accompanying  sketch. 
One-sixteenth  inch  ragging  is  used.  The  rolls  are  made  up  in  sets 
of  four,— two  middle  rolls,  one  top,  and  one  bottom  roll  making 
up  the  set.  The  rolls  are  changed  every  two  weeks,  when  a  new 
middle  roll  is  inserted  and  the  bottom  and  top  interchanged,  as 
only  passes  Nos.  1,  3,  5  and  7  have  been  used  in  the  bottom  roll  and  passes 
Nos.  2,  4  and  6  in  the  top  roll;  all  seven  passes  have,  of  course,  been  used  in 
the  middle  roll.  At  the  end  of  a  four  weeks'  period,  the  entire  set  is  returned 
to  the  roll  shop  for  dressing.  About  five  sets  are  kept  in  stock.  Recently 
the  diameter  of  the  rolls  have  been  increased,  which  permits  more  dressings 
and  gives  longer  life.  Both  adamite  and  sand  cast  iron  rolls  are  used  here, 
as  the  reductions  of  the  piece  are  small  and  no  great  strength  is  required. 
Adamite  rolls  are  annealed  and  are  very  hard.  The  sand  cast  rolls  are 
ordinary  cast  iron  of  the  following  composition,  approximately:  1.87% 
total  carbon,  1.22%  graphitic  carbon,  .65%  combined  carbon,  .37%  manga- 
nese, .070%  sulphur,  .920%  phosphorus,  .70%  silicon.  The  rolls  weigh 
18,000  to  19,000  pounds  each.  The  passes  are  7^",  7^",  6^",  6M",  5M", 
5%"  and  4"  wide.  The  sketch,  (Fig.  66)  shows  the  relative  dimensions. 
When  new,  the  rolls  have  a  collar  of  thirty  and  three-eighths  inches  diam- 
eter and  three-fourths  inch  is  taken  off  at  each  dressing  of  the  cast  iron 
rolls  and  one-fourth  inch  for  the  adamite  rolls;  the  rolls  are  scrapped  when 
the  collars  have  been  turned  down  to  a  diameter  of  twenty-eight  and  one- 
fourth  inches. 

Guide  Cages:  Two  inches  above  the  center  line  of  the  bottom  roll, 
lugs  are  attached  to  front  and  rear  of  the  roll  housings  to  support  guide 
cages.  These  cages  are  cast  steel  frames  for  holding  up  the  guides  used 
on  all  passes  of  this  mill.  They  are  bolted  to  the  housings.  The  front 
guide  cage  is  six  feet  six  and  three-fourths  inches  long,  reaching  almost  to 
the  face  of  the  housing,  and  is  about  five  feet  high.  It  contains  closed  holes 
in  front  of  all  passes  using  the  bottom  roll  and  in  front  of  No.  6  pass  of  the 
top  roll;  slots  are  provided  in  front  of  Nos.  2  and  4  passes.  The  rear  guide 
cage  is  practically  the  same  as  the  front  but  has  all  open  slots  in  front  of 
the  top  roll  passes.  Cast  steel  guides  and  side  guards  are  bolted  to  these 
guide  cages. 

Tables:  The  bloom  from  the  thirty-eight  inch  mill  comes  from  the 
shear  tables  to  the  engine  side  of  the  roll  table  for  the  twenty-eight  inch 
mill.  This  table,  together  with  the  rear  table,  is  of  the  lifting  type  and 
is  raised  and  lowered  as  a  unit  with  the  rear  table.  The  front  table  contains 
twelve  cast  steel  rollers,  each  of  which  has  five  collars  for  turning  the 
billets.  The  size  of  these  collars,  beginning  at  the  engine  side,  are:  16"  x 
2",  14"  x  12K",  15"  x  12^",  16"  x  12^",  and  16"  x  1^".  This  arrange- 
ment allows  four  grooves,  9^",  8J^",  7M"  and  6"  from  end  to  end.  The 


.396  THE  ROLLING  OF  STEEL 


diameters  of  the  rollers  at  these  grooves  are  9",  10",  11"  and  12",  respect- 
ively. The  rollers  are  driven  by  a  Crocker-Wheeler  75  h.  p.,  220  volt 
series  wound  D.  C.  Motor.  There  are  side  guards  on  the  edges  of  the  table 
and  at  the  front  end  are  side  guards  for  putting  the  bloom  from  the  thirty- 
eight  inch  mill  into  the  proper  pass  and  for  protecting  the  other  grooves. 
The  table  is  thirty-four  feet  ten  inches  from  center-line  to  center-line  of 
the  end  rollers  and  is  about,  six  feet  wide,  inside.  Coupled  to  the  front  of 
the  table  at  the  last  groove  is  an  extension  table  consisting  of  four  dead 
rollers  protected  by  side  guards;  it  is  fifteen  feet  long  and  fourteen  inches 
wide  and  is  used  as  an  extension  for  the  bar  when  ready  for  the  seventh 
pass  of  the  mill.  Both  front  and  rear  tables  are  raised  and  lowered  by 
means  of  fourteen  and  twenty-one  inch  plungers  operated  by  a  hydraulic 
cylinder;  the  hydraulic  apparatus  is  located  under  one  end  of  the  front  table 
and  is  connected  to  each  table  by  bell-cranks  from  a  main  shaft  attached  to 
the  cross-heads.  The  front  table  is  equipped  with  a  stationary  manipulator 
for  advancing  the  bars  from  pass  to  pass;  it  consists  of  four  sets  of  three 
and  one  set  of  two  cast  steel  fingers  bolted  to  pedestals  on  the  foundation 
of  the  mill.  The  fingers  are  set  between  rollers  Nos.  1  and  2,  4  and  5,  7 
and  8,  9  and  10,  and  11  and  12,  in  line  with  the  wide  collars;  they  are  flat 
cast  steel  plates  mounted  vertically  and  with  their  tops  bent  at  an  angle 
giving  a  45°  slope  in  the  direction  it  is  desired  to  move  the  piece.  The 
fingers  do  not  reach  above  the  level  of  the  pass  when  the  table  is  elevated 
and  the  bars  run  out  on  the  collars  of  the  rollers;  as  the  table  sinks,  the  bars 
encounter  the  stationary  fingers  and  slide  down  into  the  next  groove.  The 
rear  table,  as  mentioned,  is  operated  through  the  same  shaft  as  the  front 
table,  but  owing  to  the  fact  that  it  must  raise  the  bars  from  the  lower 
roll  to  the  middle  one  and  advance  them  one  pass,  it  has  to  travel  through 
an  arc  in  rising  to  bring  its  grooves  in  line  with  the  next  passes.  This  is 
done  by  causing  the  table  to  slide  toward  the  next  pass  as  it  is  raised  by 
the  use  of  pull-over  rods  attached  to  pedestals  on  the  proper  side  of  the 
bottom  of  the  scale  pit;  when  lowered,  the  table  slides  back  into  place 
again.  The  table  consists  of  twelve  cast  steel  rollers,  fourteen  inches  in 
diameter,  and  six  feet  wide,  set  three  feet  two  inches  apart,  making  a  table 
thirty-seven  feet  long;  the  rollers  are  driven  by  a  motor  similar  to  the  one 
used  on  the  front  table.  Rollers  Nos.  2,  3,  4,  5,  6,  8,  10,  and  12  have  19" x 
4"  collars  on  their  ends  for  turning  the  piece,  which  should  tumble  off 
them  as  it  comes  from  the  seventh  pass.  In  addition  there  is  a  manipulator 
in  the  first  groove;  this  consists  of  five  forged  steel  fingers  two  and  one- 
fourth  inches  wide  mounted  on  rocker  arms  attached  through  a  shaft  to  a 
plunger  in  a  cylinder  pivoted  to  a  support  on  the  floor  of  the  scale  pit.  The 
upward  motion  of  the  table  draws  the  fingers  with  it  and,  when  the  plunger 
stops  rising  in  the  cylinder,  causes  them  to  turn  the  piece  and  advance  it 
for  the  second  pass.  This  manipulator  lies  below  the  table  when  material 
is  delivered  from  the  bottom  roll  and  acts  only  to  turn  bars  90°  from  the 
first  pass  to  the  second.  The  table  is  equipped  with  three  heavy  cast  steel 


CONTINUOUS  BILLET  MILL  397 

side  guards  between  the  four  passes  which  the  material  uses  in  the  bottom 
roll.  These  reach  back  nine  feet  from  the  front  to  the  table;  there  are  also 
light  side-guards  at  each  end  of  the  rollers  reaching  the  length  of  the  table. 
These  tables  make  the  operation  of  the  mill  practically  automatic,  and 
make  it  possible  to  roll  four  pieces  at  the  same  time. 


SECTION  II. 

THE  CONTINUOUS  BILLET  MILL. 

General  Features  of  the  Continuous  Mill:  The  continuous  mill, 
often  called  a  Morgan  mill  after  the  inventor,  Chas.  H.  Morgan,  consists 
of  a  series  of  horizontal  roll  stands  arranged  one  after  the  other,  so  that 
the  piece  to  be  rolled  enters  the  first  stand  and  travels  in  a  straight  line 
through  the  mill  to  the  last  stand  where  it  issues  as  a  finished  bar,  thus 
making  but  one  pass  through  each  stand  of  rolls.  In  such  a  mill,  where 
the  piece  is  being  rolled  in  several  different  stands  at  the  same  time,  it 
is  necessary  that  the  surface  speed  of  the  different  sets  of  rolls  be  so  pro- 
portioned that  each  set  will  travel  at  a  speed  as  much  greater  than  the 
preceding  one  as  the  lengthening  of  the  piece  requires.  With  new  rolls 
and  perfect  adjustment  to  produce  the  proper  reduction,  this  relation  of 
speed  of  the  different  stands  is  easily  provided  for  by  a  system  of  driving 
gears.  To  care  for  the  wearing  down  of  the  rolls,  the  bottom  roll  is  made 
adjustable,  and  as  a  further  precaution  against  little  irregularities  that 
can't  be  overcome  by  adjustments,  each  set  of  rolls  is  purposely  set  to 
run  at  a  slightly  greater  speed  than  that  required  to  conform  to  the  speed 
of  the  preceding  set,  so  as  to  put  the  piece  under  tension  at  all  times.  For 
turning  the  piece  between  passes  twisting  guides  are  employed. 

Advantages  and  Disadvantages  of  Continuous  Mills:  High  out-put 
and  low  labor  costs  are  the  two  chief  advantages  of  this  type  of  mill.  In 
addition,  the  mills  roll  the  metal  down  very  rapidly,  thus  giving  less  time 
for  oxidation  and  permitting  more  working  in  one  heat,  and  yet  the  speed 
of  the  roll  is  low,  so  that  comparatively  little  power  is  required  to  run  them. 
Besides,  the  scrap  losses  are  low,  due  to  the  fact  that  they  can  roll  from 
blooms  of  any  length,  which  fact  makes  it  unnecessary  to  cut  the  bloom 
after  leaving  the  bloomer,  except  to  discard  for  pipe  or  other  flaws  that 
occasionally  occur.  Finally,  the  rolls  are  so  short  as  to  be  almost  un- 
breakable, and,  therefore,  very  light  rolls  may  be  used  for  comparatively 
heavy  work  with  entire  safety.  As  to  the  disadvantages,  the  great  number 
of  rolls  not  only  makes  the  first  cost  of  the  mill  very  high  but  adds  im- 
mensely to  the  cost  of  rolls  for  different  sections.  For  the  same  reason, 
much  time  is  required  for  roll  changes.  Hence,  the  mill  is  best  adapted 
to  roll  large  amounts  of  one  section  continuously.  It  is  obvious  that  com- 
plicated sections  or  those  requiring  great  accuracy  cannot  be  rolled  on 


THE  ROLLING  OF  STEEL 


such  a  mill.  These  characteristics  of  the  continuous  mill,  however,  make 
it  particularly  well  suited  for  rolling  billets,  strips,  such  as  hoop  and  cotton 
ties,  and  skelp.  They  are  also  employed  as  roughing  rolls  for  the  various 
combination  mills. 

Example  of  Continuous  Billet  Mill :  As  an  example  of  the  continuous 
billet  mill  the  fourteen  inch  number  one  mill  at  Duquesne  has  been  selected, 
because  it  is  fed  by  the  forty  inch  blooming  mill,  previously  described.  By 
this  combination  the  ingot  is  rolled  down  to  a  bloom  approximately  6"  x  4" 
in  the  forty  inch  mill  from  which  it  is  delivered  on  roll  tables,  after  the 
proper  discard  at  the  shears,  to  the  continuous  mill,  where,  without 
reheating,  the  bloom  is  reduced  to  billets  ranging  in  size  from  three  and 
one-quarter  inches  to  one  and  three-eighth  inches  square.  The  mill  con- 
sists of  ton  stands  of  rolls,  and  is  set  in  line  with  the  bloomer.  The  distance 
from  the  blooming  mill  shears  to  the  first  stand  of  rolls  is  eighty-four  feet 
eight  inches. 

Drive:  This  mill  is  driven  by  gears  from  a  line  shaft  from  an  Allis 
Chalmers  horizontal  vertical  compound  condensing  Corliss  valve 
steam  engine,  size  44"  x  78"  x  60",  with  an  indicated  horse  power  of  3500. 
This  engine  is  opposite  the  shears  and  is  set  so  its  driving  shaft  extends  in 
a  direction  parallel  to  the  mill  line.  The  engine  is  designed  to  run  at  a 
speed  of  75  r.  p.  m.  at  a  steam  pressure  of  130  Ibs.  The  maximum  torque 
the  engine  is  designed  to  give  at  the  roll  circumference  is  450,000  inch 
pounds.  The  exhaust  of  this  engine  is  taken  to  a  central  condensing  plant. 
The  line  shaft  is  coupled  to  the  crank-shaft  of  the  engine  as  follows:  A 
cast  steel  hub  is  forced  on  and  held  by  keys  to  the  end  of  the  crank-shaft. 
A  phosphor-bronze  thrust  collar  is  bolted  in  halves  over  this  joint.  The 
outer  end  of  the  hub,  three  feet  ten  inches  in  diameter,  is  bolted  to  a  short 
steel  hub  having  wobblers  twenty  inches  in  diameter  on  its  other  end.  A 
cast  iron  coupling  six  feet  ten  inches  long  fits  over  this  wobbler  and  that 
of  a  similar  but  longer  hub  at  its  outer  end.  This  hub  is  two  feet  seven 
inches  long,  of  cast  steel,  and  its  large  end,  three  feet  ten  inches  in  diameter 
is  bolted  to  a  short  hub,  twenty-one  inches  wide,  which  is  keyed  onto  the 
seventeen  inch  end  of  the  line  shaft.  The  line  shaft  of  forged  steel,  is  made 
in  two  pieces,  nine  to  thirteen  inches  diameter,  and  is  seventy-two  feet  six 
and  three-fourths  inches  long.  At  ten  points  on  the  line  shaft,  beginning 
at  the  engine  end  of  the  shaft  are  mitre  gears  respectively  4'  6",  4'  0",  3'  4^", 
3'  UK",  5'  2Y2",  5'  5",  7'  0",  5'  5%"  and  7'  11"  apart;  these  mesh  with 
mitre  gears  keyed  on  cross  over  shafts  that  lead  to  their  respective  roll 
stands.  These  gears  are  supported  by  bearing  stands  along  the  line  shaft. 
The  crossover  shafts  drive  the  mill  pinions,  and  give  to  each  set  of  rolls, 
beginning  after  No.  1  stand,  a  higher  speed  than  that  of  the  one  preceding, 
in  order  to  take  care  of  the  increased  length  of  the  bar.  The  mill  ends  of 
the  crossover  shafts  are  carried  in  bearings  supported  on  pedestals;  the 
ends  of  the  crossover  shafts  have  cast  iron  half  couplings  keyed  to  them, 
and  these  are  bolted  to  other  half  couplings  which  are  connected  to  the 


CONTINUOUS  BILLET  MILL  399 


leading  spindles  by  coupling  boxes  twelve  and  one-half  inches  long  and 
twelve  inches  in  diameter.  All  spindles,  pinions  and  coupling  boxes  on  the 
mill  are  cast  steel.  The  pods  on  the  spindles  extend  along  their  entire 
length.  The  spindles,  top  and  bottom,  are  all  of  the  same  dimensions: 
two  feet  long,  nine  inches  neck  diameter,  and  nine  and  one-half  inches  body 
diameter.  The  leading  spindles  are  cast  hollow  so  that  they  will  break 
under  excessive  strain  before  any  other  part  of  the  mill,  and  are  con- 
nected by  plain  coupling  boxes,  each  twelve  and  one-half  inches  long  and 
twelve  inches  in  diameter,  to  the  top  pinions  of  the  roll  stands. 

Pinions  and  Housings:  The  pinions  are  of  the  staggered  tooth  type 
with  three  pods.  They  are  four  feet  eight  inches  in  total  length,  fourteen 
and  three-fourths  inches  wide  across  the  face  of  the  teeth,  nine  inches  in 
diameter  at  the  wobblers,  nine  and  one-half  inches  in  diameter  at  the  necks, 
and  fourteen  and  one-fourth  inches  in  pitch  diameter  of  the  teeth,  of  which 
there  are  fourteen.  The  pinion  housings  are  cast  iron,  in  one  piece,  and 
are  bolted  to  the  pinion  shoes,  which  run  the  length  of  the  mill;  each  pair 
is  bolted  together  at  the  top  as  caps  are  not  necessary.  The  windows 
are  cast  to  shape  to  receive  the  pinion  bearing  boxes,  which  are  bolted  to 
them.  The  pinion  bearing  boxes  are  solid  cast  steel  boxes,  round  in  shape 
and  with  lugs  on  the  outer  ends  for  bolting  to  the  housings.  They  are 
babbitted  one-half  inch  deep;  their  dimensions  are  thirteen  inches  wide  in 
the  windows  and  eleven  and  three-fourths  inches  long.  The  pinions  are 
joined  to  the  rolls  by  solid  spindles  and  coupling  boxes  already  described. 

Rolls  and  Housings:  The  roll  housings  are  charcoal  cast  iron  about 
four  and  one-half  feet  high,  bolted  to  the  cast  mill  shoes;  the  mill  shoes  run 
at  right  angles  to  the  rolls  through  the  length  of  the  ten  stands.  The 
housings  have  charcoal  cast  iron  caps,  one  fitting  over  each.  The  caps  are 
notched  at  the  four  corners  to  receive  the  bolts  to  hold  them  fast  to  the 
housings,  and  in  the  center  of  each  side  is  bored  a  five  inch  hole  for  the 
phosphor-bronze  housing  nuts,  in  which  turn  the  housing  screws;  the  housing 
screws  are  of  tool  steel,  twenty-four  inches  long,  with  one  and  one-half 
threads  per  inch.  Each  housing  has  a  window  three  feet  seven  and 
three-fourths  inches  deep  and  thirteen  inches  wide,  with  a  beveled  sill  at 
the  bottom  and  a  ledge,  twenty-one  and  one-quarter  inches  above  the  sill, 
for  resting  the  carrier  bearing  for  the  top  roll.  Each  pair  of  housings  is 
held  in  line  at  the  top  by  means  of  cast  iron  separators.  The  necessary 
holes  for  set-pins  and  stud-bolts  are  drilled  into  the  housings.  The  liners 
used  are  the  ordinary  steel  plates  of  varying  thicknesses. 

Adjustment  of  the  Rolls:  The  method  of  adjusting  rolls  in  mills  of 
this  type  is  nearly  always  that  of  lining  the  bottom  roll  up  or  down  to  the 
top  roll.  A  cast  steel  screw  box,  therefore,  is  placed  on  the  sill  of  each 
housing  and  bolted  to  the  housing;  it  is  16%"  x  10"  and  is  threaded  with 
nine  half  inch  grooves,  babbitted  to  prevent  excessive  wear.  In  each  of 


400  THE  ROLLING  OF  STEEL 

these  is  placed  a  special  screw  bolt,  left-hand  thread  for  the  outside  housing 
and  right-hand  thread  for  the  inside  housing.  These  bolts  have  short 
square  ends  on  the  outer  ends  but  longer  squares  on  the  inner  ends;  the 
latter  may  be  coupled  together  by  a  cast  iron  coupling.  Above  the  screw 
bolts  and  resting  on  them  and  the  screw  boxes  are  placed  cast  steel  wedges 
fourteen  inches  long  and  eight  inches  wide,  with  nine  half  inch  grooves, 
babbitted.  The  threads  are,  of  course,  the  same  as  for  the  screw  boxes. 
On  the  wedges  are  rested  the  bottom  bearings;  these  are  steel  castings. 
On  the  bottom  they  are  provided  with  a  wedge  which  fits  against  the  screw 
wedge.  The  bearings  have  one  inch  of  babbitt  metal  lining  and  two  bronze 
bearing  pieces.  No  top  bearing  is  necessary  for  the  bottom  roll,  as  there 
is  no  upward  pressure  on  it  and  it  has  no  other  piece  to  support,  as  the 
carrier  bearing  for  the  top  roll  rests  on  the  ledge  mentioned  in  the  preceding 
paragraph.  The  breaker  blocks  are  cast  iron,  the  bottom  ends  of  the  set 
screws  resting  directly  on  them.  These  screws  are  squared  off  above  the 
threads  for  adjustment  by  wrenches,  and  are  provided  with  lock  nuts. 

Arrangement  of  Roll  Stands  and  Guides:  Owing  to  the  fact  that 
the  speed  of  travel  of  the  bar  and  hence  the  speed  of  the  rolls  is  greater 
in  each  successive  pass,  the  housings  are  placed  closer  and  closer  together 
as  the  bar  is  reduced  to  avoid  danger  of  buckling.  In  order  from  No.  1 
stand,  the  center  lines  of  the  rolls  are  at  the  following  intervals:  10'  0", 
9'  0",  8'  0",  V  0",  6'  6",  6'  0",  5'  6",  5'  6",  5'  6".  For  the  purpose  of  obtain- 
ing work  on  all  sides  of  the  bar  and  as  the  most  convenient  method  of  rolling, 
the  bar  is  twisted  between  every  other  pair  of  rolls,  and  for  this  reason 
special  guides  have  to  be  used.  They  are  of  cast  steel  made  up  especially 
for  these  stands,  so  that  they  will  give  the  bar  just  the  proper  twist  or  keep 
it  headed  right  to  enter  the  next  pair  of  the  rolls.  These  guides  are 
set  usually  in  cast  steel  guide  boxes  bolted  to  rest  bars  that  are  fastened 
in  ledges  in  the  housings;  where  necessary,  saddle  bars  are  used  to  hold 
down  the  guides  and  guide  boxes.  All  guides  are  wedged  tightly  in  place 
with  either  steel  or  wooden  wedges.  The  following  is  the  arrangement  of 
the  guides  on  this  mill:  No.  1  receiving  guide  is  a  combination  straight 
guide  and  crop  shear  bumper;  all  the  rest  of  the  receiving  guides  are  straight; 
but  the  delivery  guides  are  alternated  thus:  No.  1,  straight; No.  2,  twisting; 
No.  3,  twisting;  No.  4,  straight;  No.  5,  twisting;  No.  6,  straight;  No.  7, 
twisting;  No.  8,  straight;  No.  9,  twisting;  No.  10,  straight.  Where  the 
stands  are  far  apart  or  the  section  is  light,  the  bar  is  supported  from  below 
by  narrow  plates  reaching  from  one  delivery  guide  to  the  next  receiving 
guide  or  else  by  light  steel  side  guards. 

The  Rolls:  The  rolls  for  this  mill  are  of  the  following  dimensions: 
Total  length,  four  feet  six  inches;  length  of  barrel,  sixteen  inches;  diameter 
of  wobbler  (3-pod),  nine  inches;  diameter  neck,  ten  inches;  weight,  1500  to 
1600  pounds. 


CONTINUOUS  BILLET  MILL 401 

Table  54.     Data  Pertaining  to  Rolls  for  a  14"  Continuous  Billet  Mill. 

STAND    COMPOSITION    No.  GROOVES    BODY  DIAMETER    BEFORE  TURNING 

Top  Bottom 

1  Steel  1  13%"  13%" 

2  1  13%"  13%" 

3  "  2  13%" 

4  Adamite  2  13^" 

5  "  2  141^" 

6  2  14M"  13%" 

7  Chill  Iron  4  13%"  13%" 

8  "  4  13M"  13%" 

9  4  14%"  14" 
10  4  14%"  14%" 

Six  inches  is  allowed  between  the  centers  of  the  grooves  when  only  two 
grooves  are  cut,  but  only  three  and  three-fourths  inches  is  allowed  in  the 
case  of  four-groove  rolls.  Following  is  a  table  of  the  speed  of  the  rolls  of 
each  successive  stand  and  the  observed  delivery  speed  of  the  bar  coming 
out  of  it  with  the  engine  at  normal  speed  of  75  r.  p.  m. 


Table  55.  Speed   Ratios  on   Fourteen   Inch   Continuous  Billet  Mill. 

STAND  SPEED  OF  ROLLS —  DELIVERY  SPEED  OF  BAR 

REVOLUTIONS  PER  MINUTE  FEET  PER  MINUTE 

1  17  46.7 

2  21.4  54.5 

3  24.55  67.1 

4  30.9  .   99.2 

5  36.6  126.3 

6  44.6  156. 

7  57.6  188. 

8  68.7  242. 

9  89.1  326. 
10  117.9  417. 


Cropping  Shears:  Between  the  receiving  table  to  the  mill  and  the 
first  stand  of  rolls  are  hydraulic  shears,  pressure  450  Ibs.  per  square  inch; 
through  these  shears  all  blooms  for  the  fourteen  inch  No.  1  mill  pass.  They 
are  capable  of  cutting  blooms  up  to  7"xll"  in  size,  but  their  usual  work  is 
on  6"  x  4"  blooms.  They  are  used  to  cut  crops  from  the  front  end  of  the 
bloom  so  it  will  enter  No.  1  stand  easily.  When  necessary  they  may  be 
used  for  shearing  off  pipes  and  bad  pieces  that  have  escaped  discard  at  the 


402 


THE  ROLLING  OF  STEEL 


I 

N 

o   1  Stand 

H 

SU*1 

Steel 


FIQ.  67.     Rolls  and  Passes  for 


CONTINUOUS  BILLET  MILL 


403 


the  Continuous  Billet  Mill. 


404  THE  ROLLING  OF  STEEL 

blooming  mill  shears,  and  for  severing  the  bloom  in  case  of  a  cobble.  They 
are  capable  of  a  ten  inch  swing  from  the  base,  and  at  the  end  of  their  stroke 
they  strike  the  combined  guide  and  bumper  previously  mentioned  as  the 
No.  1  guide.  They  are  thrown  back  into  position  automatically,  when  the 
bloom  is  cut,  by  a  heavy  coil  spring.  The  stroke  of  the  knife  blade  is  ten 
inches.  The  shears  are  vertical  acting  with  the  top  blade  actuated  by  the 
cylinder.  No.  10  stand  delivers  the  finished  billet  directly  onto  the  receiv- 
ing table  for  the  steam  flying  shears;  this  table  and  its  delivery  table  are 
driven  through  bevel  gears  on  a  single  line  shaft;  the  line  shaft  is  driven 
by  a  jack  shaft  geared  to  a  primary  jack  shaft  which  is  in  turn  geared  to 
the  crossover  shaft  for  No.  10  stand.  As  various  numbers  of  stands  are 
used  for  the  various  sizes  of  billets,  the  corresponding  sizes  of  bars  have 
a  different  delivery  speed  and  the  shears  receiving  table  must,  therefore, 
be  driven  proportionately,  so  that  the  billet  maybe  cut  by  the  flying  shears 
without  buckling  and  may  be  carried  away,  when  cut,  fast  enough  to  keep 
clear  of  the  next  billet.  Accordingly,  various  sizes  of  gear  wheels  are 
provided  for  the  jack  shaft  to  the  table.  The  surface  speed  of  the  roll 
table  may  be  set  at  various  rates  to  suit  the  delivery  speed  of  the  billet 
by  changing  the  gears  on  the  jack  shaft. 

Flying  Shears:  The  flying  shears  roll-table  consists  of  eight  cast  steel 
rollers, — two,  sixteen  inches  in  diameter,  dn  the  receiving  side  of  the  shears 
and  six,  ten  inches  in  diameter,  on  the  delivery  side.  The  rollers  are  notched 
with  a  V-shaped  groove  so  as  to  hold  the  bar,  as  it  comes  to  the  shears, 
with  one  of  its  diagonals  in  the  vertical,  as  it  is  in  this  position  when  it 
leaves  the  last  pass  of  the  rolls  and  must  be  sheared  in  the  same  position. 
The  flying  shears  are  placed  with  the  center  line  of  their  knives  twenty  feet 
beyond  the  center  line  of  No.  10  stand.  The  shears  are  actuated  by  a 
30"  x  20"  steam  cylinder.  The  action  of  the  shears  is  speeded  up  or  slowed 
down  according  to  the  delivery  speed  of  the  billet.  Cutting  under  fifteen 
foot  lengths  is  not  attempted  for  fear  of  not  getting  the  shears  back  to 
position  in  time  to  prevent  buckling  of  the  next  billet.  The  knives  on  the 
shears  have  a  life  of  from  three  to  sixty  hours;  and  they  have  to  be  changed 
for  every  size  of  billet.  They  have  a  half  inch  clearance  above  the  square 
being  cut.  The  horizontal  stroke  of  the  shears  is  ten  inches. 

Hot  Beds :  The  flying  shears  deliver  upon  a  table  125  feet  long,  from 
which  steam  operated  rollers  and  pushers  convey  the  bars  to  four  hot  beds 
extending  at  right  angles  to  the  tables.  All  of  these  are  controlled  from 
a  pulpit  in  the  yard.  The  rollers  at  the  foot  of  No.  1  bed  are  skewed  so  as 
to  bring  the  billets  against  the  first  pusher  and  make  them  lie  parallel 
with  it;  all  the  other  rollers  are,  as  usual,  set  at  right  angles  to  the  pieces. ' 
At  four  points  on  the  table  are  hydraulically  operated  stoppers  for  stopping 
the  bars  at  the  hot  bed  desired  or  allowing  them  to  pass  to  the  horizontal 
scrap  bed  beyond  the  last  hot  bed.  The  hot  beds  are  sloped  up  at  a  slight 
angle  and  are  each  thirty-one  feet  wide  by  fifty-three  feet  six  inches 


CONTINUOUS  BILLET  MILL 


405 


•W^^r- .^^JS 


Fia.  68.     14"  Continuous  Mill — 4"  x  6"  Blooms  to  2"  Billets. 
Drawings  from  Actual  Sections. 


406  THE  ROLLING  OF  STEEL 

long.  They  are  built  of  rails,  and  the  material  is  moved  on  each  by  a  steam 
pusher  connected  to  a  cable,  driven  through  gears  by  two  8"  x  10"  vertical 
twin  simple  50  h.  p.  steam  engines.  Cold  pushers  are  also  cable  connected 
by  gears  and  driven  by  similar  engines,  but  of  the  horizontal  type.  They 
convey  the  billets  desired  to  the  end  of  the  bed  and  slide  them  over  rail 
ends  from  the  beds  into  railroad  cars  just  below  the  hot  bed  level.  Alligator 
scrap  shears  are  provided  at  the  end  of  the  scrap  bed,  which  is  hand  operated. 
The  accompanying  prints  are  intended  to  show  the  forms  of  the 
rolls,  their  kinds,  shape  of  the  various  passes,  and  the  different  stages  in 
the  reduction  of  the  bloom  to  the  billet. 


SECTION  III. 

ROLLING  OF   SHEET  BARS   AND   SKELP 

Difficulties  and  Methods  of  Rolling  Semi=Finished  Flats:  This 
material  may  or  may  not  be  rolled  from  the  original  heat  of  the  ingot.  At 
Duquesne,  sheet  bar,  as  well  as  billets  and  splice  bars,  is  rolled  on  the 
twenty-one  inch  mill  from  the  original  heat  of  the  ingot,  which,  being  first 
reduced  to  a  &W  x  1Y±"  bloom  on  the  thirty-eight  inch  mill,  is  passed  to 
the  twenty-eight  inch  billet  mill  and  on  to  the  twenty-one  inch  mill  without 
reheating.  At  Edgar  Thomson,  for  example,  the  9}^"  x  9J/6"  bloom  from 
the  three-high  blooming  mill  is  reheated,  when  the  rolling  is  completed  on 
the  No.  4  mill,  which  consists  of  a  single  train  of  three  stands  of  three-high 
rolls,  or  on  one  of  the  rail  mills,  usually  the  number  one.  However,  the 
method  employed  in  reducing  the  material  is  the  same,  except  as  to  details 
of  handling,  which,  of  course,  must  be  changed  to  suit  the  different  mills. 
Because  the  twenty-one  inch  mill  at  Duquesne  represents  a  distinct  type 
of  mill,  this  mill  is  selected  as  an  example  of  a  mill  rolling  sheet  bar.  The 
problem  to  be  overcome  in  rolling  these  flats  lies  in  the  difficulty  of  con- 
trolling the  width.  In  rolling  blooms,  billets  and  small  slabs,  the  piece 
is  held  to  dimensions,  not  only  by  the  shape  of  the  grooves,  but  also  by 
edging  the  piece  in  certain  of  the  passes.  But  in  rolling  sheet  bar,  the 
thinness  of  the  piece  will  not  permit  edging,  after  it  leaves  the  roughers. 

The  Tongue  and  Groove  Pass:  For  the  purpose  of  controlling  the 
width  and  at  the  same  time  effecting  a  heavy  reduction  in  the  sectional 
area,  a  form  of  closed  box  pass,  called  the  tongue  and  groove  pass,  is  used. 
In  this  form  of  pass  a  groove,  corresponding  in  width  to  the  width  of  the 
piece  desired,  is  cut  in  one  of  the  rolls  which  encloses  one  side  and  the 
edges  of  the  piece  in  rolling,  while  a  tongue,  cut  on  the  opposite  roll,  fits 
into  the  groove,  thus  closing  the  pass  on  the  fourth  side.  The  designing 
of  this  pass  presents  some  very  interesting  features.  In  order  to  insure  a 
proper  delivery  of  the  pieces  from  the  rolls  and  provide  for  fitting  the  tongue 
into  the  groove,  the  sides  of  the  latter  are  cut  at  a  slight  angle  to  the  bottom. 
Owing  to  the  heavy  drafts  taken,  the  metal  is  squeezed  up  into  the  clearance 
between  the  tongue  and  the  edges  of  the  groove,  thus  forming  a  fin  on  each 


SHEET  BAR 


407 


111 

1 

4"v4"  Rillpt       Go 

fr 

\ 

_r^i 

Sheet  Bar 

XV      r-t 

Bar 

/ 

k_Z_J 

K      ?      -> 

No.  1  Stand-4'  x4"  Billet,  Common  Splice  and  Sheet  Bar 


D    i 

>1         J                  Dummy  Pass 

u 

„ 

^ 

V-^,-V 

\               4"x4"  to  14"  Mill 

L     i 

No.  2  Stand  for  Sheet  Bar 


No   3  Stand  for  Rolling  Sheet  Bar 


>Vo.  4  Stand  for  Rolling  Sheet  Bar 


No  5  Stand 


Noa.  5  and  6  Stands  for  Rolling  Sheet  Bar 

Fio.  69.     Roll  Stands  for  Boiling  eight  inch  Sheet  Bar. 


408  THE  ROLLING  OF  STEEL 

side  of  the  piece,  unless  precautions  are  taken  to  prevent  it.  These  fins 
are  prevented  from  forming  by  cutting  the  groove  with  fillets  at  the  edges, 
and  arranging  them  so  that  the  bevelled  edges  of  the  piece  formed  by  the 
fillets  enter  the  succeeding  pass  opposite  the  openings  formed  by  the  clear- 
ance between  the  rolls.  In  this  way  no  fin  is  formed,  because  the  spreading 
of  the  material  merely  fills  out  the  bevel  of  the  fillet,  leaving  no  excess 
metal  to  be  squeezed  up  between  the  rolls.  To  enter  the  first  tongue  and 
groove  roll  the  edges  of  the  billet  are  well  rounded  off,  which  prevents 
more  than  a  very  slight  fin  forming  in  this  pass.  Since  the  piece  is  to  be 
finished  in  plain  rolls,  no  fillet  is  placed  in  the  last  tongue  and  groove  pass. 
The  accompanying  prints  show  the  forms  of  these  passes,  and  the  different 
steps  in  the  reduction  from  the  billet  to  sheet  bar. 


P«M  *«•*    .  -.*?"•   . 

FIG.  70.      Rolling  Tongue  and  Groove  for  8  inch  Sheet  Bar. 

Sheet  Bar  is  all  approximately  eight  inches  wide  and  varies  in  thickness 
to  give  weights,  per  linear  foot,  from  seven  to  forty-three  pounds.  The  gauge 
in  inches  is  found  by  multiplying  the  weight  per  foot  by  .0372  in  which  factor 
the  weight  of  a  cubic  inch  of  steel  is  taken  to  be  .28 pounds.  After  the  mill  is 
once  set  for  rolling  sheet  bar,  the  different  weights  of  bar  are  obtained  by 
varying  the  distance  between  the  rolls.  As  there  is  considerable  difference 
in  temperature  in  different  billets  when  rolled,  as  at  this  mill,  from  the 
original  heat  of  the  ingot,  it  is  difficult  to  hold  the  thickness  constant  at 
the  finishing  stand,  and,  in  order  to  keep  the  thickness  uniform,  a  man  is 
stationed  at  this  stand  of  rolls  to  adjust  the  screws  up  or  down  to  suit  the 
temperature  of  the  bar.  As  it  is  necessary  to  produce  a  very  smooth  surface 
on  sheet  bar,  on  account  of  its  being  subsequently  rolled  into  thin  sheets, 
chilled  rolls  are  used  in  the  finishing  stands.  For  the  same  reason,  water 
and  steam  jets  must  be  directed  against  both  surfaces  of  the  bar  in  order 
to  remove  the  scale.  These  jets  are  used  both  at  the  rolls  and  at  the  saws. 

Example  of  a  Mill  Rolling  Sheet  Bar— The  Twenty=one  Inch  Mill 
at  Duquesne:  As  previously  stated,  this  mill  represents  a  distinct  type. 
The  design  aims  to  secure  the  advantages  of  the  continuous  mill  and  elimi- 
nate the  disadvantages.  So,  while  it  is  practically  continuous  in  action  the 
different  stands  of  rolls  are  placed  so  far  apart  that  the  piece  clears  one 
stand  before  it  enters  the  next.  As  a  tandem  arrangement  alone  would 


SHEET  BAR  409 


spread  the  mill  out  over  a  too  great  length,  the  various  stands  of  rolls  are 
usually  arranged  in  trains  that  are  in  tandem.  Such  a  layout  requires  long 
roll  tables  for  carrying  the  piece  forward  and  suitable  apparatuses  for 
transferring  the  piece  transversely,  such  as  lifting  cradles,  skids,  diagonal 
roll  tables,  and  switch,  or  divided,  tables.  In  this  respect  the  twenty-one 
inch  mill  at  Duquesne  is  a  good  example. 

The  Layout  for  This  Mill,  as  for  all  mills  of  this  type,  is  somewhat 
complicated.  The  mill  consists  of  six  stands  of  rolls  arranged  in  two  trains, 
separately  driven  and  of  three  stands  each.  The  two  trains  are  separated 
by  a  distance  of  119  feet.  In  each  train  the  first  and  second  stands  next 
to  the  engine  are  three-high,  while  the  third,  on  the  end  of  the  train,  is 
two-high.  For  convenience  the  different  stands  are  numbered  in  the  order 
in  which  the  material  passes  through  them.  Observing  this  order,  then, 
stands  Nos.  1,  4  and  5  compose  the  first  train,  while  stands  Nos.  2,  3  and  6 
make  up  the  second  train.  The  first  stand  is  located  105  feet  beyond  the 
twenty-eight  inch  mill  and  is  provided  with  a  receiving  table  fifty-three 
feet  six  inches  long,  equipped  with  switches  for  guiding  the  material  from 
the  twenty-eight  inch  mill  into  the  different  passes  in  the  first  stand  of 
the  twenty-one  inch  mill.  These  passes  are  three  in  number,  all  of  different 
sizes,  one  of  which  is  employed  as  a  finishing  pass  for  billets  and  the  other 
two  as  working  passes  on  material  to  be  finished  on  the  twenty-one  inch 
mill. 

Arrangement  of  the  Roll  Tables:  The  delivery  table  for  No.  1  stand 
is  provided  with  a  center  guard  for  diverting  material  to  the  billet  table 
that  leads  to  the  4"  x  4"  billet  shears,  located  beyond  No.  2  stand.  Further 
along,  by  means  of  a  switching  device  another  division  of  the  material 
may  be  made,  thus  sending  billets  either  through  a  dummy  pass  in  N6.  2 
stand  to  the  fourteen  inch  No.  2  continuous  mill,  located  about  100  feet 
beyond,  or  to  a  working  pass,  when  the  material  is  to  be  finished  at  the 
twenty-one  inch  mill.  Since  material  must  be  cut  into  suitable  lengths  for 
rolling  on  the  twenty-one  inch  mill,  a  hydraulic  shear  is  located  77  feet 
from  No.  1  stand  and  arranged  to  cut  on  the  twenty-one  inch  mill-half  of 
the  table  only.  The  receiving  table  for  the  No.  2  stand  begins  at  these 
shears.  It  is  provided  with  a  stop  which  may  be  set  for  lengths  from 
twelve  and  one-half  to  thirty-eight  feet.  A  manipulator  for  turning  the 
piece  is  also  provided  in  this  table.  The  delivery  table  for  No.  2  stand  is 
65  feet  long  and  has  ten  rollers  fifteen  inches  in  diameter  and  twenty  inches 
long;  these  rollers  are  separated  by  a  side-guard  from  the  rollers  leading 
to  the  fourteen  inch  mill  No.  2.  In  connection  with  this  table  is  a  transfer 
skid  table  for  moving  the  piece  to  the  receiving  table  for  No.  3  stand.  It 
consists  essentially  of  a  frame  of  rails  bolted  together  and  hinged  to  the 
table,  onto  which  they  are  to  deliver  the  steel.  The  frame,  when  in  its 
lowest  position,  lies  below  the  roller  tables,  so  that  when  the  transfer  is 
raised,  it  picks  up  the  steel,  which  slides  down  the  rail  skids  onto  the  table. 


410  THE  ROLLING  OF  STEEL 


The  skids  are  greased  so  that  the  steel  will  slide  more  easily.  The  frame 
is  raised  and  lowered  by  means  of  links  keyed  to  a  line  shaft  which  is  in 
turn  operated  by  a  hydraulic  cylinder.  The  transfer  raises  the  bars  twenty 
inches  from  the  top  of  the  delivery  table  No.  2  to  the  top  of  the  rollers 
of  the  receiving  table  of  No.  3  stand,  the  distance  between  the  two  tables 
being  eight  feet  three  inches.  As  No.  3  stand  is  often  used  as  a  three-high 
stand  this  table  is  of  the  tilting  type,  and  operated  by  an  hydraulic  cylinder 
placed  near  the  stand.  The  delivery  table  of  No.  3  stand  is  109  feet  long 
and  serves  also  as  a  receiving  table  for  No.  4  stand.  It  is  stationary  and,  in 
order  to  receive  the  material  when  No.  3  stand  is  operated  two-high  as 
well  as  three-high,  it  is  inclined,  extending  from  the  top  of  the  bottom 
roll  of  No.  3  stand  to  the  top  of  the  middle  roll  in  No.  4  stand.  Collars 
on  its  rolls  serve  to  turn  the  piece  between  the  stands,  and  its  side  guards 
are  adjustable  so  that  they  may  be  used  to  guide  the  piece  into  different 
passes  on  No.  4  stand.  The  delivery  table  for  No.  4  stand  is  79  feet  long, 
and  has  guards  on  the  side  next  to  the  engine  only,  in  order  that  the  piece 
may  be  transferred  by  means  of  a  skid  table  to  the  receiving  table  for 
No.  5  stand.  This  transfer  table  is  similar  to  that  between  No.  2  and  No.  3 
stands  except  that  the  piece  here  slides  to  a  lower  level,  where  it  is  stopped 
by  the  guards  on  the  receiving  table  for  No.  5  stand.  Connecting  No.  5 
and  No.  6  stands  is  a  stationary  table  provided  with  adjustable  side  guards 
and  vertical  rollers  for  edging  the  piece  as  required. 

Hot  Saws  and  Shears:  The  delivery  table  of  the  last,  or  No.  6,  stand 
is  about  104  feet  long,  and  at  its  farther  end  are  located  two  electrically 
driven  hot  saws  set  thirty  feet  six  inches  apart.  These  saws,  made  of  .80% 
carbon  steel,  are  forty-two  inches  in  diameter  and  one-fourth  inch  thick. 
This  table  feeds  into  a  shear  table,  one  hundred  three  feet  nine  inches  long, 
along  which  are  situated  seven  electrically  operated  shears.  These  shears 
are  adjusted  to  cut  at  any  lengths  up  to  ninety-seven  feet  six  inches,  which 
is  the  maximum  distance  between  the  first  and  last  shears.  They  may  be 
made  to  cut  in  unison  or  separately,  as  desired.  From  the  shear  table  the 
piece  may  take  a  straight  course  to  the  sheet  bar  shears  and  bundling  cradle, 
or  be  diverted  to  the  hot  beds  which  are  used  for  billets  and  splice  bars. 
Returning  now  to  the  billets  from  No.  1  stand,  it  was  mentioned  that  4"  x  4" 
billets  could  be  diverted  to  a  shear.  This  shear,  of  the  duplex  type,  is 
located  several  feet  beyond  No.  2  stand  and  is  provided  with  a  bisected 
table  of  which  each  part  leads  to  one  of  the  two  blades  of  the  shears.  A 
gauge  and  automatic  stopper,  mounted  on  a  gauge  beam  about  two  feet 
above  the  delivery  tables  for  the  shears,  can  be  set  at  one-quarter  inch 
intervals  for  any  lengths  from  twenty-three  and  one-half  inches  to  twenty 
feet.  From  these  shears,  an  elevated  inclined  roller  conveyor  carries  the 
short  billets  to  eight  bins,  each  of  which  has  a  capacity  of  30  tons  and  is 
located  so  as  to  empty  directly  into  railroad  cars  by  gravity. 

Drive:  Each  train  is  direct  driven  by  a  William  Tod  Co.  34"  x  58" 
x  60"  tandem  compound  horizontal  condensing  engine  of  3500  h.  p.  The 


SHEET  BAR  MILL  411 


usual  speed  of  these  engines  is  67  r.  p.  m.  but  they  can  be  run  .as  high  as 
82  r.  p.  m.  Both  trains  are  direct  driven  through  a  pinion  shaft  from  the 
crank-shaft  of  the  engine.  The  connections  between  engine  and  mill  and 
between  the  stands  of  rolls  are  made  in  a  manner  exactly  similar  for  both 
trains,  so  that  one  description  will  suffice  for  both.  To  the  end  of  the 
engine  crank  shaft  is  keyed  a  half  coupling  of  cast  steel,  and  over  it  is  bolted 
a  thrust  collar.  A  second  half  coupling  is  bolted  to  the  one  next  the  engine. 
A  compound  coupling  box — two  feet  two  and  one-half  inches  in  diameter  on 
the  engine  end  and  nineteen  and  one-half  inches  on  the  mill  end  and  nineteen 
and  one-half  inches  long  for  No.  1  train  of  rolls,  and  a  similar  box  but  two 
feet  two  and  one-half  inches  in  diameter  on  the  engine  end  and  twenty-three 
and  one-half  inches  in  diameter  on  the  mill  end  and  nineteen  and  one-half 
inches  long  for  No.  2  train  of  rolls — fits  over  the  wobbler  of  the  second  half- 
coupling  and  the  mill  end  wobbler  of  the  leading  spindle.  The  leading 
spindle  for  No.  1  train  is  three  feet  four  and  three-fourths  inches  long,  and 
twelve  inches  in  diameter,  and  has  three  pods  on  the  engine  and  four  on  the 
mill  end.  For  No.  2  train  the  leading  spindle  is  four  feet  one  and  one-half 
inches  long,  sixteen  inches  in  diameter  on  the  engine  end,  where  it  has 
three  pods,  and  twelve  inches  in  diameter  on  the  mill  end,  which  has  four 
pods;  this  spindle  has  twelve  and  one-half  inches  near  the  center  turned 
smooth  to  a  fifteen  inch  diameter  for  a  rider  bearing.  A  coupling  box 
of  cast  steel,  fifteen  inches  long  and  seventeen  and  one-half  inches  in  diameter, 
connects  the  leading  spindle  to  the  center  pinion  of  the  three  in  the  pinion 
housings. 

Pinions  and  Housings:  These  pinions  are  plain  steel  castings,  six 
feet  three  inches  long,  with  a  pitch  diameter  of  twenty-one  inches,  a  neck 
diameter  of  thirteen  inches,  a  wobbler  diameter  of  twelve  inches,  and  a 
width  of  twenty-four  inches  across  the  face  of  the  teeth.  There  are  eleven 
teeth,  of  six  inches  pitch,  cut  in  the  helical  manner.  There  are  three  pinions, 
set  one  above  the  other  in  their  proper  bearings  in  cast  steel  pinion  housings. 
These  housings  stand  about  five  feet  eight  inches  above  the  mill  floor  and 
are  bolted  to  the  mill  shoes;  their  windows  are  twenty-two  and  one-half 
inches  wide  and  five  feet  eight  inches  deep,  beveled  at  the  bottom,  and 
are  provided  with  forged  steel  side  liners,  five  feet  four  and  seven-sixteenths 
inches  long  and  two  and  three-fourths  inches  thick,  and  cast  steel  bottom 
liners,  35"  x  12"  x  2".  The  housings  are  drilled  for  the  necessary  holes  for 
set  pins,  stud  bolts,  cap  bolts,  etc.  One  steel  cast  pinion  housing  cap  covers 
the  housings;  at  its  four  corners  are  drilled  four  inch  holes  for  the  cap  bolts 
which  are  three  feet  five  inches  long,  and  are  held  in  by  a  nut  at  the  bottom 
and  a  key  at  the  top.  In  the  middle  are  fastened  two  hooked  lifting  bolts, 
for  enabling  the  crane  to  get  hold  when  the  caps  are  to  be  removed.  The 
bearings  are  all  of  the  solid  type,  of  cast  steel,  and  babbitted.  Coupling 
boxes,  similar  to  the  one  connecting  the  leading  spindle  to  the  middle  pinion, 
connect  the  three  pinions  to  their  respective  spindles.  The  spindles  are 
steel  castings  with  wobblers  of  four  pods  each,  extending  from  end  to  end; 


412  THE  ROLLING  OF  STEEL 

they  are  three  feet  six  inches  long  and  twelve  inches  in  diameter.  They 
are  supported  on  the  mill  end  by  another  set  of  similar  coupling  boxes 
which  connect  them  to  the  rolls. 

Rolls  and  Roll  Housings :  The  rolls  on  this  mill  are  twenty-six  inches 
long  on  the  body  for  all  stands  except  No.  3  which  is  thirty-six  inches, 
because,  being  a  three-high  stand,  it  contains  a  greater  number  of  passes 
than  the  two-high  stands.  The  collars  are  usually  twenty-two  and  one- 
half  inches  in  diameter;  the  body  diameters  range  from  fifteen  to  twenty- 
seven  inches;  the  diameter  of  the  necks  is  thirteen  inches,  and  of  the  wobblers 
twelve  inches.  The  total  length  is  six  feet  ten  inches  for  the  rolls  on  No.  3 
stand  and  six  feet  for  the  rest.  The  rolls  range  in  weight  from  3800  pounds 
to  7000  pounds.  The  rolls  are  cut  down  each  time  they  are  dressed  one- 
eighth  to  three-eighths  of  an  inch  until  a  collar  diameter  of  nineteen  inches 
is  reached,  when  they  are  scrapped.  The  rolls  are  of  the  following  materials 
for  the  various  products  rolled: 

No.  1  Stand — Usually  sand  roll;  rarely  steel. 

No.  2  Stand — Sand  Roll  for  billets  and  common  splice  bars;  steel  in 
majority  of  cases  for  Duquesne  and  continuous  rail 
joint;  always  steel  for  sheet  bar. 

No.  3  Stand — Sand  Roll  for  billets  and  common  splice  bar;  sometimes 
the  top  roll  for  common  splice  bar  is  steel.  Steel  always 
for  sheet  bar  and  nearly  always  for  Duquesne  and  con- 
tinuous rail  joint;  otherwise  cast  iron. 

No.  4  Stand — Sand  Rolls  always  for  everything. 

Nos.  5  and  6  Stands — Always  sand  rolls  except  for  sheet  bar;  sheet 
bar  requires  chilled  iron  rolls. 

About  three  sets  of  billet  rolls,  about  three  sets  of  cast  iron  rolls  for 
sheet  bar  and  five  sets  of  chilled  rolls,  two  sets  of  common  splice  bar  rolls  for 
No.  6  stand  and  one  set  of  other  rolls  are  carried  on  hand;  For  rail  joints  rolls 
are  turned  up  as  needed,  and  all  splice  bar  rolls  are  ordered  new  when  speci- 
fications for  a  new  section  come  in.  The  roll  housings  for  the  twenty-one 
inch  mill  are  similar  for  stands  Nos.  1,  2,  3,  and  4,  which  can  be  used  as 
three-high,  and  for  Nos.  5  and  6  which  are  only  two-high.  In  No.  1  train, 
the  rolls  in  No.  1  stand  are  connected  by  spindle  and  coupling  boxes  to  those 
in  No.  4  stand  and  the  bottom  two  of  No.  4  are  connected  to  No.  5  rolls. 
No.  2  train  is  similarly  connected;  the  top  roll  of  Nos.  1  and  2  stands  is  a 
dummy  acting  as  a  spindle  and  the  bottom  rolls  in  Nos.  1  and  4  stands 
act  the  same  way.  The  spindles,  except  those  between  No.  3  and  No.  4 
stands,  are  two  feet  nine  inches  long  and  twelve  inches  in  diameter;  the 
latter  are  three  feet  six  inches  long  and  twelve  inches  in  diameter.  The 
coupling  boxes  are  all  fifteen  inches  long  and  seventeen  and  one-half  inches 
in  diameter.  The  roll  housings  are  cast  iron,  held  in  line,  top  and  bottom, 
by  cast  iron  separators.  For  Nos.  1,  2,  3,  and  4  stands  the  housings  stand 


DEFECTS  IN  BLOOMS  AND  BILLETS  413 

five  feet  eight  and  one-half  inches  above  the  mill  shoes  and  have  twenty- 
two  and  one-half  inch  windows;  those  for  Nos.  5  and  6  stands  rise  three 
feet  eleven  and  three-fourths  inches  above  the  shoes  and  have  twenty-two 
and  one-half  inch  windows.  From  each  housing  there  are  two  cast  iron 
caps,  held  down  by  square  key  bolts,  fitting  through  five  inch  square  holes 
in  the  caps.  In  the  center  of  each  cap  is  cast  a  hole  for  receiving  a  phosphor 
bronze  housing-nut,  which  is  pressed  into  the  cap  and  threaded  for  receiving 
the  housing  screw.  This  screw,  which  is  made  of  open  hearth  steel  'of 
.36%  to  .40%  carbon,  is  five  and  three-eighths  inches  in  diameter  at  the  base 
and  is  threaded  at  a  one  inch  pitch.  On  all  stands  but  No.  6,  a  cast  steel 
rosette  is  fastened  on  top  of  the  housing  screws  to  provide  means  for  turning 
them.  They  thus  hold  the  top  rolls  tightly  down.  On  No.  6  stand  a  cast 
steel  disc  is  used  instead  of  a  rosette,  and  a  long  lever  is  attached 
to  it,  which  in  turn  is  held  in  place  by  means  of  bolts  through  slots  in  the 
outer  edge  of  the  disc.  The  bottom  bearings  for  Nos.  1,  2,  and  3  stands, 
as  well  as  all  the  riders  and  the  carrier  bearings  are  of  cast  steel.  Brass 
bearing  pieces  are  used  in  some,  but  not  in  all,  of  the  housings.  The  pre- 
ceding prints  show  how  the  mill  may  be  used  for  rolling  billets  as  well  as 
sheet  bar.  The  rolling  of  rail  joints,  to  be  described  later,  is  gradually 
being  discontinued  on  this  mill,  the  intention  being  to  transfer  this  business 
to  Edgar  Thomson  Works. 


SECTION   IV. 

SOME    GENERAL  PRECAUTIONS   TO  BE   OBSERVED  IN    ROLLING 
SEMI-FINISHED   PRODUCTS. 

Reasons  for  Studying  Defects:  A  great  many  of  the  precautions 
necessary  to  observe  in  rolling  the  semi-finished  products  have  been 
mentioned  at  various  times  in  preceding  pages.  However,  as  failure  to 
observe  the  proper  precautions  in  rolling  gives  rise  to  defects  in  the  material 
which  may  show  up  in  the  finished  article  and  as  the  reader  may  be  par- 
ticularly interested  in  this  phase  of  the  business,  it  is  thought  that  a  list 
of  rolling  defects  and  their  causes  may  be  found  useful  and  interesting. 
By  giving  the  cause  for  each,  it  will  be  shown  that  many  defects  are  unavoid- 
able, and  that  even  the  most  rigid  inspection  will  not  suffice  to  eliminate 
some  defects  which  are  a  common  annoyance  to  the  manufacturer  and 
consumer  alike. 

Rough  Surface  Due  to  Scale:  One  of  the  defects  common  to  semi- 
finished material  and  one  that  often  shows  up  in  the  finished  article  is  a 
very  rough  or  pitted  surface.  That  this  roughness  most  often  is  due  to 
the  adherence  of  scale  on  the  surface  of  the  ingot  during  the  rolling  there 
can  be  little  doubt,  because  a  careful  examination  of  such  defects  will 
generally  reveal  its  presence  in  these  pits.  At  first  thought  this  defect  is 
likely  to  be  attributed  to  a  rolling  of  the  scale  into  the  surface,  and  the 
remedy  at  once  suggested  is  to  clean  the  ingot  of  scale  during  rolling.  But 


414  THE  ROLLING  OF  STEEL 

failure  to  remove  the  scale  from  the  ingot  will  not  always  account  for  this 
roughness.  In  such  cases  the  blame  for  the  defect  is  to  be  laid  to  the 
presence  of  blow  holes  near  the  surface,  which  in  the  heating  of  the  ingot 
in  the  soaking  pit  become  filled  with  molten  oxides.  The  presence  of  the 
oxide  may  be  attributed  to  two  causes,  namely,  to  the  oxidation  of  the 
surface  of  the  blow  holes  or  to  its  introduction  through  small  openings 
which  lead  from  the  blow  holes  to  the  surface  of  the  ingot.  Thus,  if  the 
ingot  is  subject  to  a  temperature  sufficiently  high  to  fuse  the  oxides,  the 
oxide  in  the  hole  will  melt,  or  the  liquid  oxide  on  the  surface  will  flow  through 
these  openings  to  the  blow  holes  beneath  and  partially  or  completely  fill 
these  small  cavities.  This  oxide  cannot  be  removed,  and  when  the  ingot 
is  rolled,  it  becomes  so  firmly  embedded  in  the  surface  that  even  subsequent 
pickling  will  not  remove  it.  The  only  correction  remaining  for  such  defects, 
then,  is  the  very  expensive  one  of  chipping  or  grinding.  Low  carbon 
chrome-nickel  steel  is  very  susceptible  to  this  fault,  and  it  is  very  difficult  to 
clean  the  scale  from  its  surface.  While  this  peculiarity  of  nickel  steel  may  be 
attributed  to  the  same  cause  as  that  just  cited  for  plain  steels,  there  is 
much  evidence  to  show  that  scale  pitting  in  this  case  is  partly  due  to  an 
entirely  different  cause,  namely,  the  reduction  of  the  oxide  of  nickel  by 
metallic  iron  at  the  rolling  temperature  of  this  steel.  Thus,  as  fast  as  this 
alloying  element  is  oxidized  on  the  surface,  its  oxide  is  reduced  by  the  free 
iron  beneath,  the  result  being  the  formation  of  iron  oxide  under  the  surface 
of  the  metal.  This  condition  gives  rise  to  an  outer  layer  composed  of 
metallic  alloy  mingled  with  oxide,  in  which  the  oxide  acts  as  a  binder 
between  metal  and  surface  scale.  It  can  readily  be  seen  that  this  layer 
may  vary  in  thickness,  and  the  merging  from  all  metal  to  all  oxide  is  gradual, 
resulting  in  what  may  be  termed  an  interpenetration  of  metal  and  oxides, 
which  causes  the  scale  to  adhere  most  firmly  to  the  surface. 

Cobbling:  The  most  frequent  failure  in  rolling  is  cobbling.  It  occurs 
at  the  bloomers  as  a  turn  down  or  twisting  of  the  piece  in  the  rolls,  at  the 
rougher  in  the  same  way  or  by  catching  and  buckling  on  the  roll  table, 
and  at  the  other  mills  as  a  roll  table  or  mill  accident.  The  piece  may 
catch  on  a  table  and  buckle  up  and  be  prevented  from  coming  through  the 
rolls;  it  may  catch  against  a  guide  and  buckle;  or  it  may  buckle  against 
the  rolls,  if  delivered  to  them  too  fast.  In  such  cases,  practically  all  of  the 
piece  has  to  be  scrapped;  the  uninjured  sections  of  partially  cobbled  blooms 
can  usually  be  finished  and  be  made  use  of. 

Laps:  An  over  filling  of  a  pass  causes  the  steel  to  spread  between  the 
collars  of  the*  rolls  and  causes  a  lap;  this  is  usually  rolled  down  into  the 
surface,  partially  or  altogether,  if  the  steel  is  turned  for  the  next  pass, 
and  the  place  between  the  lap  and  the  rest  of  the  piece  is  left  as  a  surface 
crack,  or  seam.  A  lap  may  result  from  a  crack  in  the  rolls  into  which  the 
steel  flows. 

Collar  Marks :  Owing  to  overdraft  or  possibly  defective  heating,  or, 
in  the  blooming  mill,  to  too  infrequent  turning  of  the  piece,  the  steel  will 
overfill  the  groove,  causing  collar  marks.  Lack  of  alignment  or  proper 


DEFECTS  IN  BLOOMS  AND  BILLETS  415 

adjustment  of  the  rolls  or  any  other  incident  that  gives  an  unequal  draught 
will  cause  the  collars  to  bite  into  the  bloom  and  injure  it.  Collaring  leaves 
deep  cuts  that  can  seldom  be  rolled  out,  hence  the  injured  portion  of  the 
bloom  is  discarded  at  the  shears. 

Guide  Marks:  Guides,  if  they  are  too  deep,  out  of  line,  or  required 
to  do  too  heavy  duty  will  score  the  surface  of  the  steel,  usually,  in  fine 
lines,  or  else  may  tear  its  edges. 

Ragging  Marks:  Ragging  leaves  protrusions  on  the  surface  of  the 
steel,  and  sometimes  these  are  lapped  over,  showing  in  the  finished  steel 
in  irregular  seams  and  cracks.  On  mills  rolling  steel  that  is  to  be  rolled  to 
small  section  or  a  fine  finish,  only  light  ragging  is  used. 

Off  Size :  If  a  bloom,  slab,  or  billet  is  off  size,  it  makes  the  weight 
of  the  predetermined  cut  different  from  the  actual  cut  and  will  prevent  an 
order  from  being  accurately  filled,  or  may  even  cause  a  deficit  of  steel  to 
apply  on  the  order.  On  mills  of  the  class  in  question  it  is  difficult  to  work 
to  absolutely  correct  sizes,  hence,  a  tolerance  for  weight  as  well  as  for 
size  should  be  given. 

Unequal  Draughts:  These  defects  are  due  to  the  rolls  being  out  of 
parallel  with  each  other,  causing  one  side  to  be  rolled  light  and  the  other 
heavy.  This  condition  may  result  also  in  a  turning  down  of  a  lap  in  the 
next  pass  in  the  case  of  a  bloom,  or  a  cobble  in  the  case  of  a  billet. 

Seams:  Seams  may  be  caused  by  blow  holes,  by  laps,  or  by  tearing 
of  the  steel  due  to  causes  which  will  be  explained  in  a  succeeding 
paragraph.  Slivers  or  scale,  first  rolled  into  the  surface,  and  then  torn 
out,  may  leave  cracks  that  will  roll  down  to  form  seams.  Seams  may  also 
be  caused  by  too  much  belly  in  the  roll,  or  by  not  turning  the  piece  often 
enough  during  the  rolling  of  the  bloom,  as  illustrated  in  Fig.  71.  Seams 
are  especially  injurious  in  steels  for  forgings  and  for  heat  treatment.  They 
seldom  fail  to  cause  the  steel  to  crack  in  quenching,  particularly  if  the  steel 
is  quenched  in  water. 

Slivers :  Slivers  are  due  to  defective  teeming  of  the  molten  steel  and 
to  a  tearing  of  the  corners  of  the  steel  in  blooming,  roughing,  or  finishing. 
Tearing  is  attributed  to  many  things,  such  as  over  oxidation  in  the  open 
hearth,  burning,  twisting  in  the  rolls,  and  improperly  adjusted  guides.  Soft 
steels  and  high  sulphur  screw  stock  are  especially  subject  to  these  defects. 

Scabs :    Scabs  are  found  on  steel  if  it  is  burned  or  if  scale  is  rolled  into  it. 

Shearing  Defects:  Failure  to  discard  properly  at  the  shears  may 
result  in  rejection  of  product.  Aside  from  this  neglect,  other  defects  may 
be  produced  by  the  shearing.  Thus,  a  dull  shear  knife  or  one  with  too 
great  clearance  will  not  make  a  clean  cut  and  will  leave  a  lip  on  the  side 
of  the  steel  where  its  stroke  ends.  An  unavoidable  effect  of  shearing  is 
to  produce  what  may  be  termed  a  mechanical  or  manufactured  pipe.  In 
the  shearing  of  billets  and  slabs,  especially  in  the  case  of  4"  x  4"  billets  and 
larger,  it  frequently  occurs  that  the  sheared  end  shows  a  pulled-out  con- 


416 


THE  ROLLING  OF  STEEL 


FIG.  71.     Good  and  Bad  Practice  in  Rolling  Blooms. 
Top  bloom  shows  effect  of  not  turning  the  bloom  often  enough. 


DEFECTS  IN  BLOOMS  AND  BILLETS  417 

dition.  There  are  a  number  of  things  responsible  for  this  condition  on  the 
sheared  ends.  Thus,  highly  segregated  steel  will  not  shear  uniformly  and 
often  results  in  a  pulled-out  condition,  and  the  same  thing  is  almost  sure  to 
happen  in  case  the  billet  or  bloom  has  a  spongy  center.  The  temperature 
at  which  the  billets  are  sheared  plays  a  very  important  part,  also.  These 
pulled-out  cavities  on  the  sheared  end  may  have  a  depth  of  more  than 
one  inch.  It  is  readily  seen  what  happens  when  such  billets  are  re- 
heated and  rolled  into  small  sizes.  The  pull-out  is  closed  up  and  elongated 
with  the  rolling,  and  when  rolled  into  a  small  rod  or  any  other  smaller 
shape  the  effect  of  this  pull-out  condition  may  extend  far  back  into  the 
finished  material.  Very  often  this  manufactured  pipe  is  mistaken  for  a 
genuine  metallurgical  pipe,  since  in  most  cases  it  is  centrally  located.  The 
injurious  effect  of  a  manufactured  pipe  on  the  physical  properties  of  steel 
is  similar  to  that  of  a  metallurgical  pipe. 

Splits  or  Cracks  in  Billets  and  Blooms:  In  breaking  down  ingots  it 
often  happens  that  the  metal  does  not  yield  properly  to  the  draught,  and 
the  surface  structure  is  cracked  or  torn  at  a  number  of  places,  and  some- 
times to  a  depth  of  two  or  three  inches.  As  the  rolling  is  continued,  these  torn 
surfaces  are  gradually  closed,  but  not  perfectly  welded,  and  become  much 
elongated,  so  that  it  is  not  easy  to  detect  them  in  the  finished  article,  not 
only  because  they  are  completely  closed  but  because  of  the  new  scale,  which, 
forming  after  the  rolling  is  finished,  totally  covers  up  all  signs  of  their 
presence.  This  feature  makes  their  occurrence  all  the  more  serious,  because, 
though  their  dangerous  character  is  recognized  by  the  manufacturer,  and 
every  attempt  is  made  to  eliminate  them,  the  inability  to  detect  them 
often  leads  to  their  passing  the  inspection.  These  cracks  are  attributed 
to  many  causes.  In  the  first  place,  certain  grades  of  steel,  more  particu- 
larly those  in  which  the  carbon  content  lies  between  .18%  and  .22%,  are 
more  susceptible  to  this  defect  than  others.  The  sulphur  and  manganese 
content  also  appears  to  affect  the  tendency  of  ingots  to  crack.  Hence, 
many  steel  men  are  inclined  to  lay  most  of  the  blame  to  chemical  compo- 
sition, while  others  hold  that  the  fault  lies  in  improper  treatment  in  manu- 
facture. It  is  a  fact  that  steel  not  properly  made  may  be  red  short,  and 
that  the  steel  can  be  injured  through  too  heavy  draught  and  too  much  reduc- 
tion without  turning,  or  poorly  designed  passes  in  rolling  cannot  be  denied. 
It  also  appears  that  the  heating  of  the  ingot  in  the  pits  may  exert  an  impor- 
tant influence  upon  the  rolling  properties  of  the  steel. 

Inspection:  Blooms,  billets,  and  slabs  are  inspected  on  the  mill 
yard,  and  when  defects  are  not  very  deep,  they  are  chipped  out  with  chipping 
hammers,  if  so  ordered,  before  the  steel  is  shipped.  All  inspection  is 
directed  to  the  elimination  of  the  defects  listed  above,  and  rejection  is 
according  to  the  strictness  of  the  order  in  respect  to  this  requirement. 
Billets  and  sheet  bars  are  hot  bed  inspected,  and  in  addition  to  inspection 
for  surface  defects  sheet  bar  is  also  tested  for  exactness  of  weight. 


418  ROLLING  FINISHED  PRODUCTS 


CHAPTER  VII. 

THE  ROLLING  OF  THE  HEAVIER  FINISHED  PRODUCTS- 
PLATES. 

SECTION   I. 

PREPARATION  OF  THE    STEEL  FOR   ROLLING   FINISHED   PRODUCTS. 

Reheating:  While  a  few  finished  steel  articles,  such  as  plates,  large 
rails  and  heavy  shapes,  which  on  account  of  their  large  mass  retain  their 
heat  for  a  considerable  length  of  time,  may  be  rolled  by  rapid  methods 
directly  from  the  ingot  without  reheating,  the  majority  of  articles  are  so 
small  that  their  temperature  would  fall  far  below  the  rolling  range  before 
the  great  amount  of  reduction  required  could  be  accomplished.  For  all  such 
articles  a  reheating  of  the  bloom,  billet,  or  slab  is  a  necessary  step  pre- 
liminary to  rolling.  Needless  to  say,  this  reheating  of  the  steel  is  a  matter  of 
great  importance  and  requires  even  more  care  than  the  heating  of  ingots. 
Compared  with  hot  ingots  the  nature  of  heating  is  very  different,  for  here  all 
the  heat  is  conducted  toward  the  center  from  the  surfaces  exposed  to  it; 
and  since  in  practice  it  is  well  nigh  impossible  to  expose  all  surfaces  equally 
to  the  heating  medium,  uneven  heating  is  likely  to  occur,  the  result  of  which 
is  a  variation  in  the  dimensions  of  the  finished  section.  Here,  too,  as  with 
ingots,  the  danger  of  burning  or  overheating  is  ever  present.  As  the  tem- 
peratures attained  are  far  above  the  critical  range,  the  reheating  tends  to 
undo  the  refining  of  the  previous  rolling.  Since  the  extent  of  this  obliter- 
ation of  the  original  structure  is  about  in  proportion  to  the  temperature 
above  the  critical  attained  it  is  desirable  to  keep  the  reheating  temper- 
ature as  low  as  possible,  and  to  finish  the  rolling  as  near  the  critical  range 
as  practicable.  However,  some  finished  materials  are  so  light  that  the 
highest  temperatures  attainable  without  injury  to  the  steel  is  barely 
sufficient  to  complete  *he  rolling,  and  in  addition  the  wear-and-tear  on  the 
mills  incident  to  rolling  at  the  lower  temperatures  increases  so  rapidly  as 
to  add  very  much  to  the  expense  of  rolling.  Again,  the  surface  of  the 
metal  is  oxidized  very  rapidly  in  a  flame  or  a  hot  atmosphere  even  slightly 
oxidizing,  and  this  oxidation  results  in  the  formation  of  an  insulating  coat  of 
scale  that  retards  the  heating.  This  sc  ale  may  cause  trouble  in  other  ways, 
also,  because,  at  the  temperature  which  it  is  often  necessary  to  maintain  in 
the  furnace  in  order  to  heat  the  steel  to  the  proper  temperature  for  rolling, 


REHEATING  FOR  ROLLING  419 

it  becomes  pasty  or  quite  fluid,  and  blooms  or  billets  in  contact  in  the  furnace 
are  often  cemented  together  by  it.  Besides,  the  surface  of  the  piece, 
being  covered  with  this  pasty  scale,  is  liable  to  cause  pieces  of  brick,  sand, 
or  other  foreign  substances  to  adhere  to  it,  and  these,  being  rolled  into 
the  steel,  produce  serious  surface  defects  in  the  finished  material,  some  of 
which  are  known  as  scabs,  brick  spots,  pitted  surfaces,  etc.  The  loss  of 
metal  due  to  the  formation  of  scale  will  sometimes  amount  to  as  much  as 
5%  and  is  seldom  under  2%. 

Types  of  Reheating  Furnaces:  Reheating  furnaces  cannot  as  yet  be 
said  to  have  reached  a  standard  in  design  and  construction.  They  are, 
therefore,  of  various  forms  and  types,  and  each  furnace  is  constructed  along 
lines  which  were  thought  to  be  the  best  suited  to  the  local  conditions  at 
the  time  of  its  erection.  Most  of  these  furnaces  are,  however,  of  the 
reverberatory  type,  and  may  be  fired  with  either  coal  or  gas  for  fuel,  though 
the  gaseous  fuels  are  much  preferred  for  this  purpose  on  account  of  the  ease 
with  which  the  temperature  may  be  regulated.  In  order  to  conserve  the 
heat  as  much  as  possible,  they  may  be  provided  with  waste  heat  boilers 
or  be  constructed  on  the  regenerative  or  recuperative  principles.  New 
mills,  however,  the  majority  of  which  are  being  electrically  driven*  cannot 
employ  the  waste  heat  boilers.  The  more  modern  furnaces  are,  then, 
built  either  on  the  regenerative  or  the  recuperative  principle,  in  both  of 
which  gaseous  or  liquid  fuels  or  pulverized  coal  are  used. 

The  Regenerative  Reheating  Furnace  is  similar  in  working  principle 
to  an  open  hearth  steel  furnace.  Gas  and  air  ports  at  each  end  of  the 
furnace  are  connected  by  flues  that  lead  to  checker  chambers,  made  of  the 
proper  refractory  materials  for  retaining  the  heat  from  waste  gases  and 
giving  up  the  same  to  ingoing  air,  or  air  and  gas  if  producer  gas  is  used, 
the  current  being  reversed  at  certain  intervals  of  time.  Unlike  the  open 
hearth  furnace,  however,  the  checker  work  for  these  furnaces  is  usually 
placed  under  the  furnace,  and,  instead  of  the  basin-like  hearth,  the  reheating 
furnace  is  provided  with  a  floor  practically  on  a  level  with  the  door  sills. 
A  low  bridge  wall,  which  separates  this  floor  from  the  up-and-down  takes, 
forms  a  kind  of  combustion  chamber  and  prevents  the  flame  from  impinging 
directly  upon  the  steel.  Above  this  combustion  chamber  the  roof  of  the 
furnace  slopes  downward  toward  the  middle  of  the  furnace  and  reverberates 
the  heat  of  the  flame  upon  the  floor.  The  steel  is  charged  through  lifting 
doors  in  one  side  of  the  furnace,  and  it  may  be  drawn  either  through  these 
same  doors  or  through  doors  in  the  opposite  side.  Originally,  it  was  the 
general  practice  to  line  the  bottom  of  these  furnaces  with  refractory  siliceous 
sand,  hence  they  are  often  called  sand  bottom  furnaces.  As  the  scale  in 
melting  unites  with  this  sand  to  form  a  slag  of  a  too  high  per  cent,  of  silica 
to  be  used  economically,  these  furnaces  are  now  made  up  of  magnesite  or 
cinder,  which,  melted  into  place,  makes  it  possible  to  use  the  resulting 
cindor  in  the  open-hearth  or  blast  furnace.  These  furnaces  are  used  mainly 


420 


ROLLING  FINISHED  PRODUCTS 


REHEATING  FURNACES  421 


for  reheating  heavy  material,  such  as  blooms,  slabs,  and  the  larger  billets, 
for  which  purpose  they  are  very  well  adapted. 

The  Recuperative  or  "Continuous"  Furnace  works  upon  the  principle 
of  counter-currents  throughout.  The  combustion  chamber  is  located  at 
one  end  of  the  furnace,  where  the  heated  steel  is  drawn,  while  the  chamber 
for  recovery  of  the  waste  heat  is  located  at  the  opposite  end,  which  is 
always  nearest  the  stack  and  where  the  steel  is  charged.  In  one  current, 
the  hot  gases  and  flame  from  the  combustion  chamber  are  drawn  by  the 
chimney  draft  over  the  floor,  which  is  separated  from  the  combustion 
chamber  by  a  bridge  wall,  and  then  downward  through  a  series  of  spaced 
iron  pipes  to  the  stack  flue.  In  the  other  current  the  course  of  the  steel 
and  the  air  for  combustion  run  counter-current  to  the  heat,  the  steel  over 
the  floor  of  the  furnace,  the  air  through  the  enclosed  space  about  the  hot 
pipes  and  a  flue  under  the  floor  to  the  combustion  chamber.  The  passage 
of  all  may,  therefore,  be  made  continuous,  hence  the  name,  continuous 
furnace.  It  will  be  observed  that  the  billets  move  from  the  coldest  part 
of  the  furnace  to  the  hottest  part,  hence  they  are  heated  very  gradually, 
reaching  the  rolling  temperature  just  prior  to  drawing.  The  scale,  there- 
fore, does  not  melt,  and  no  slag  is  formed  in  the  continuous  furnace  if  it  is 
fired  with  gas,  oil  or  tar.  When  powdered  coal  is  used  for  fuel,  the  silicious 
ash  unites  with  the  scale  to  form  an  easily  fused  slag  that  collects  at  the 
discharge  end  of  the  furnace.  In  order  to  push  the  billets  through  the 
furnace  suitable  pushing  devices  must  be  provided,  and  to  aid  in  this  work 
the  floor  of  the  furnace  is  sometimes  inclined,  sloping  downward  from  the 
charging  to  the  drawing  end.  To  prevent  the  tearing  up  of  the  floor,  skids 
for  supporting  the  billets  are  provided,  built  into  the  bottom.  These  skids 
are  generally  made  of  heavy  pipe  through  which  a  stream  of  water  flows  to 
keep  them  cool.  An  objectionable  feature  in  the  use  of  the  skids  is  that 
they  cause  cold  spots  in  the  steel  where  the  billets  rest  upon  them.  To 
overcome  this  defect  the  pipes  are  bent  or  off-set  at  the  lower  ends,  or  the 
billets  may  be  delivered  from  the  skids  to  a  section  of  the  bottom  lined 
with  magnesite.  In  this  way  the  temperature  of  the  cold  spots  is  restored 
to  near  that  of  the  rest  of  the  billet. 

The  Advantages  of  Continuous  Reheating  Furnaces  are  numerous. 
In  the  first  place,  they  are  the  best  type  of  furnace  to  precede  a  continuous 
mill.  The  use  of  complicated  charging  and  drawing  machines  is  avoided. 
The  heating,  being  confined  to  one  end  of  the  furnace,  makes  it  easy  to 
regulate  the  temperature  to  suit  the  different  grades  of  steel,  and  to  heat 
to  the  rolling  temperature  only  those  billets  that  are  to  be  used  at  once. 
Where  the  billets  used  are  of  constant  length,  the  width  of  the  furnace  is 
so  proportioned  to  the  length  of  billet  that  the  entire  bottom  is  covered 
with  the  steel  to  be  heated.  Thus,  there  are  no  vacant  areas  on  the  bottom 
to  decrease  the  heating  efficiency  of  the  furnace.  The  accompanying 
prints  are  intended  to  show  the  chief  features  in  the  modern  construction 
of  these  two  types  of  furnaces. 


422 


ROLLING  FINISHED  PRODUCTS 


FIG  73      Continuous  Heating  Furnace. 


SHEARED  PLATE  423 


SECTION   II. 

THE    ROLLING   OF   SHEARED   PLATES. 

Methods  of  Rolling  Plates:  As  previously  indicated,  plates  may  bo 
rolled  either  from  ingots  or  from  slabs,  and  on  several  different  types  of 
mills.  Thus,  in  England,  and  a  few  places  in  this  country,  Birmingham, 
for  example,  plates  are  rolled  on  a  two-high  reversing  mill  consisting  of  a 
train  of  two  stands  of  plain  rolls.  In  these  mills,  the  stand  nearer  the  engine 
has  both  rolls  driven  and  is  used  for  roughing,  while  the  second  stand  is 
used'  for  finishing  and  has,  therefore,  only  the  bottom  roll  driven.  In  the 
majority  of  these  mills  the  rolls  are  run  hot,  that  is,  no  attempt  is  made  to 
cool  the  rolls  during  the  rolling.  In  America  the  practice  for  rolling  plates 
is  entirely  different.  In  all  cases  the  rolls  are  kept  cold  by  directing  streams 
or  sprays  of  water  upon  them  during  the  rolling,  and  two  types  of  mill, 
neither  of  which  is  like  the  English  mills,  are  used.  One  of  these,  the 
universal  mill,  has  already  been  mentioned,  and  will  be  described  more  in 
detail  later,  while  the  other,  the  invention  of  Mr.  B.  C.  Lauth,  of  Pitts- 
burgh, is  a  kind  of  three-high  mill.  In  this  mill  the  top  and  bottom  rolls 
are  driven,  are  of  the  same  size,  and  of  large  diameters,  while  the  middle 
roll  is  friction  driven  and,  in  diameter,  is  usually  about  two-thirds  the  size 
of  the  other  two  rolls.  The  maximum  size  of  the  middle  roll  is  determined 
by  the  width  of  the  housing  windows,  as  the  roll  is  removed  by  passing  it 
endways  through  this  opening.  The  top  roll  can  be  raised  and  lowered  in 
the  housing,  and  the  middle  roll,  through  suitable  levers  hydraulically  or 
electrically  operated,  can  be  brought  into  contact  alternately  with  the  top 
and  bottom  rolls,  which  then  play  the  part  of  re-enforcing  rolls.  Thus,  in 
making  the  bottom  pass,  the  plate  passes  between  this  niiddle  roll  and  the 
bottom  roll,  while  the  top  roll  is  used  as  a  re-enforcing  roll.  On  the  return 
pass,  the  middle  roll  is  dropped  down  upon  the  bottom  roll,  and  the  piece, 
having  been  raised  to  the  proper  level  by  a  tilting  table,  passes  between  the 
top  and  middle  rolls.  In  either  case,  the  amount  of  draught  is  controlled  by 
screw  downs  acting  against  the  top  roll  in  a  manner  somewhat  like  that 
of  the  blooming  mill.  The  advantage  of  this  construction  will  become 
apparent  as  this  study  advances.  Plates  rolled  on  this  mill  must  be  sheared 
on  all  edges,  hence  they  are  called  "sheared  plates"  to  distinguish  them 
from  universal  mill  plates  which  are  sheared  only  on  the  ends  to  obtain 
the  lengths  required.  The  size  of  the  sheared  plate  mill  is  determined  by 
tha  length  of  the  bodies  of  its  rolls,  while  universal  mills  are  distinguished 
by  the  maximum  spread  of  the  vertical  rolls. 

The  One  Hundred  Forty  Inch  Mill  at  Homestead  as  ah  Example  of 
a  Sheared  Plate  Mill:  In  this  mill  the  top  and  bottom  rolls,  which  must 
be  carefully  matched  and  of  exactly  the  same  diameter,  are  each  approxi- 
mately thirty-eight  and  three-fourths  inches  in  diameter  when  new,  and 


424  ROLLING  FINISHED  PRODUCTS 

the  middle  roll  twenty-two  inches.  All  three  are  chilled  rolls,  the  depth 
of  the  chill  being  between  one  and  one  and  one-half  inches.  The  bottom 
roll  is  held  in  place  by  bottom  and  side  bearings  of  brass,  which  are  fitted 
into  the  bottom  of  the  cast  steel  housings.  For  the  top  roll,  which  requires 
both  top  and  bottom  as  well  as  side  bearings,  riders  for  containing  the 
brasses  are  provided.  This  roll  is  supported  from  below  by  steel-yard  rods 
which  extend  from  the  bottom  rider  to  the  shorter  arms  of  counterbalanced 
levers  in  the  pits  beneath  the  mill.  In  this  respect  as  well  as  in  the  method 
of  screwing  down  the  top  roll,  the  construction  of  the  mill  resembles  the 
forty-inch  mill  at  Duquesne.  For  driving  the  screws,  however,  a  60  h.  p. 
motor  is  provided,  instead  of  the  hydraulic  cylinder,  and  is  connected  to 
the  screws  through  a  worm  shaft  and  crown  gear.  For  indicating  the 
draught  on  the  mill  a  large  drum  or  cylinder,  about  four  feet  in  diameter 
and  with  an  altitude  equal  to  the  total  lift  of  the  mill,  is  mounted  on  the 
top  of  one  of  the  screws.  The  surface  of  this  cylinder  is  divided  vertically 
into  parallel  spaces,  the  width  of  which  equals  the  pitch  of  the  screws,  one 
and  one-quarter  inches.  The  circumference  of  each  circle  separating  a  pair 
of  spaces  is  then  divided  by  vertical  lines  into  a  number  of  equal  parts. 
By  means  of  this  arrangement  and  a  stationary  pointer,  mounted  on  the 
housing  beside  the  cylinder  and  set  to  point  at  zero  on  the  drum  when  all 
the  rolls  are  in  contact  and  screwed  down  tight,  the  distance  between  the 
rolls  may  be  read  off  direct  and  with  great  accuracy.  For  holding  the 
middle  roll  in  place,  bearing  boxes  with  side  bearings  which  fit  into  chocks 
placed  on  the  side  of  the  housing  windows  are  provided.  For  keeping 
this  roll  in  line,  liners  are  employed,  and  for  raising  and  lowering  it,  a  rest 
bar  built  on  the  plan  of  a.  swinging  lever  is  fitted  over  each  neck  outside 
of  the  housing  and  across  the  window.  One  end  of  each  rest  bar  is  supported 
at  an  almost  constant  level  by  means  of  a  turn  buckle  rod  hung  from  the 
top  of  the  housing,  while  the  opposite  end  is  connected  to  the  plunger  of 
a  hydraulic  cylinder  which,  located  in  the  pit  beneath  the  housings,  furnishes 
the  power  for  raising  and  lowering  the  roll.  In  many  cases  this  cylinder 
is  located  on  top  of  the  housings,  and  in  the  most  recently  constructed  mills, 
electric  motors  are  employed  instead  of  the  hydraulic  cylinder. 

The  Drive  and  Connections :  The  top  and  bottom  rolls  are  connected 
to  the  pinions  through  coupling  boxes  and  spindles  similar  to  those  in  the 
blooming  mill.  The  spindles  are  eleven  feet  long,  and  both  are  supported  at 
their  centers  by  suitable  bearings.  The  saddle  box  for  the  vibrating 
spindle  is  attached  at  one  end  to  the  pinion  housing  and  at  the  other  to 
the  roll  bearing  box,  thus  keeping  the  motion  of  the  saddle  and  spindle 
co-incident  with  that  of  the  top  roll.  Since  the  middle  roll  of  the  mill  is 
friction  driven,  the  middle  pinion  is  used  as  a  driving  pinion  only,  and  is 
smaller  than  the  top  and  bottom  ones,  the  speed  ratio  being  11  to  19.  The 
pinions  are  of  the  helical  toothed  type  and  are  held  in  cast  steel  housings. 
A  short  spindle,  four  feet  eleven  inches  long,  connects  the  middle  pinion  to 
the  driving  shaft  of  the  engine  on  which  is  mounted  the  fly  wheel.  This 


SHEARED  PLATE  425 


mill  is  driven  by  a  42"  x  66"  x  60"  tandem  compound  engine,  capable  of 
giving  3500  h.  p.  at  the  speed  of  64  r.  p.  m.  Nearly  all  the  new  mills  built 
since  1916  are  electrically  driven.  The  new  one  hundred  ten  inch  mill  at 
Homestead,  otherwise  known  as  the  Liberty  mill,  is  so  driven.  This  motor 
was  built  and  installed  by  the  .General  Electric  Co.  It  is  designed  to 
develop  4000  h.  p.  and  to  give  a  speed  of  82  r.  p.  m.  on  full  load.  It  uses 
alternating  3-phase  current  with  a  frequency  of  25  cycles  per  second  and  a 
pressure  of  6600  volts.  The  installation  is  marked  for  its  simplicity;  the 
peak  loads  are  taken  care  of  by  means  of  a  55-ton  fly  wheel  mounted  on 
the  same  shaft  with  the  motor. 

Difficulties  in  Rolling  Sheared  Plates:  While  the  rolling  of  plate 
may  appear  to  the  novice  as  one  of  the  simplest  of  rolling  operations,  yet 
there  are  problems  connected  with  the  rolling  of  wide  plate  that  require 
the  combined  skill  and  experience  of  the  heater,  the  millwright,  the  roller, 
and  roll  designer  to  overcome.  If  the  slabs  are  not  heated  uniformly  in 
all  parts,  the  plates  will  curl  and  buckle  in  rolling,  while  a  similar  effect 
is  produced  if  the  rolls  are  even  slightly  out  of  alignment.  The  stretch 
of  the  housings  and  the  stoving  up  of  the  screw  are  minor  considerations 
in  overcoming  the  difficulties  of  rolling  exactly  to  gauge.  The  wearing 
away  of  the  rolls,  which  in  actual  operation,  takes  place  faster  in  the  middle 
portions  than  at  the  ends,  causes  them  to  become  hollow  in  a  short  time  so 
that  the  plate  is  thicker  in  the  middle  than  at  the  edges.  Since  the  pressure 
for  rolling  must  be  applied  at  the  ends  of  the  rolls,  this  effect  is  increased 
by  the  bending  of  the  rolls.  The  opposite  effect  would  be  produced  if  the 
rolls  should  become  hot  in  the  middle,  the  expansion  causing  an  increase  in 
their  diameters.  This  last  complication  is  avoided  by  keeping  the  rolls  cold 
with  water  sprays  above  them.  This  water,  running  down  upon  the  plate, 
has  a  tendency  to  cool  it  faster,  but  this  cooling  is  not  as  rapid  as  might 
be  expected,  because  the  water1  assumes  the  spheroidal  state  on  striking 
the  very  hot  plate  and  glides  off  without  being  vaporized  to  any  great 
extent.  At  the  one  hundred  forty  inch  mill,  the  spring  and  wear  in  the 
rolls  are  provided  for  in  the  following  manner :  To  remove  the  effects  of  wear 
the  top  and  bottom  rolls  are  dressed  do wn every  Saturday, either  in  position 
by  attaching  an  electrically  driven  reduction  gear  to  the  driving  pinion, 
which  virtually  converts  the  mill  into  a  lathe,  or  by  removing  them  and 
sending  them  to  be  lathe  turned  in  the  machine  shop.  -  To  neutralize  the 
spring  in  the  rolls  the  middle  roll  is  turned  so  that  its  diameter  at  the  middle 
is  a  little  greater  than  that  at  the  ends.  If  this  swell  or  belly  in  the  roll 
were  made  to  fit  the  top  and  bottom  rolls  it  would  almost  represent  an 
arc  of  a  very  large  circle,  but  as  it  is  impossible  to  dress  the  roll  in  this 
way,  the  lines  are  cut  only  approximately  correct  by  tapering  the  ends  and 
leaving  the  central  portion  of  the  roll  cylindrical  in  form.  The  amount  of 
the  taper  will  vary  with  the  hollowness  of  the  mill,  but  is  never  less  than 


426  ROLLING  FINISHED  PRODUCTS 

one  sixty-fourth  nor  greater  than  three  sixty-fourths  of  an  inch,  thus  making 
the  difference  in  diameter  between  the  ends  and  the  center  vary  from  one- 
thirty-second  to  three-thirty-seconds  of  an  inch.  The  distance  from  the 
end  of  the  roll  to  which  the  taper  extends  may  vary  from  forty-six  to  fifty- 
six  inches,  thus  making  the  central  cylindrical  portion  twenty-eight  to 
forty-eight  inches  long,  and  depends  upon  the  width  of  plate  being  rolled. 
It  is  the  practice,  when  advantageous,  to  roll  the  wide  plates  at  the  begin- 
ning of  the  week,  while  the  mill  is  full,  and  to  roll  the  narrower  plates  at 
the  end  of  the  week  when  the  rolls  have  been  worn  down,  and  the  hollow- 
ness  of  the  mill  is  more  pronounced.  Even  with  these  changes  the  mill 
will  often  become  so  hollow  that  it  is  necessary  to  roll  the  edges  a  little 
below  gauge  in  order  to  get  the  weight  correct.  Hollowness  in  the  mill 
tends  to  make  the  edges  of  the  plate  dovetail  or  buckle.  During  the  week 
the  middle  roll  will  be  changed  four  to  six  times. 

The  Rolling  Process  on  this  mill,  as  on  the  English  mill,  may  be  looked 
upon  as  being  performed  in  two  steps  or  stages,  namely,  a  roughing  or 
breaking  down  stage  and  a  finishing  stage.  In  the  breaking  down  of  the 
slab  the  most  important  feature  of  the  rolling  is  the  determination  of  the 
draughts,  the  size  of  slab  and  the  spring  of  the  rolls  being  the  controlling 
factors  ift  this  regard.  With  a  heavy  slab,  that  is,  one  six  to  ten  inches 
thick,  a  maximum  draft,  or  bite,  of  about  three-fourths  inch  is  possible. 
The  amount  of  bite  decreases  as  the  slab  thickness  decreases  and  the  width 
increases.  The  greater  the  surface  the  less  the  possible  draught  on  account 
of  the  greater  amount  of  work  necessary  in  rolling.  Following  the  first 
few  passes  the  draughts  become  smaller  and  smaller  because  of  the  increased 
work  required  and  also  to  allow  material  for  the  finishing.  At  least  one- 
fourth  inch  is  allowed  for  the  finishing  passes,  as  this  amount  is  required 
to  give  sufficient  material  with  which  to  remove  the  effect  produced  by 
the  spring  of  the  rolls.  Were  the  spring  not  removed,  that  is  if  the  plates 
were  finished  by  a  continuance  of  passes  carrying  the  heavy  draughts,  the 
middle  of  the  resulting  plates  would  be  much  heavier  than  the  sides.  By 
decreasing  the  draughts  the  "spring"  is  removed,  and  the  plate  approaches 
nearer  the  desired  weight  and  gauge.  Blind  passes,  that  is,  passes  in  which 
no  additional  pressure  is  applied  to  the  rolls,  are  also  used  in  finishing  for 
the  same  reason.  The  heavier  gauge  plates  cause  less  spring  in  the  roll 
and  fewer  finishing  passes  are  necessary,  while  with  light  gauge  plates, 
especially  on  a  full  mill,  it  is  necessary  to  start  the  finishing  when  about 
one-half  inch  above  the  final  gauge,  since  a  bigger  draught  is  necessary  to 
hold  the  plate  and  prevent  buckling.  Near  the  beginning  of  the  rolling, 
the  slabs  are  passed  through  the  mill  transversely  a  few  times  to  obtain 
the  desired  width  and  are  then  rolled  longitudinally.  In  gauging  the  width 
six  inches  are  allowed  for  shrinkage,  shearing,  etc.,  on  plate  not  over  eighty- 
five  inches  wide,  while  seven  to  eight  inches  are  allowed  on  plate  from 


\ 
SHEARED  PLATE  427 


ninety  inches  to  the  maximum  of  a  hundred  thirty-two  inches.  Extra 
allowance  on  the  wide  plates  is  necessary  to  take  care  of  the  overlap,  or 
lamination,  of  the  top  and  bottom  sides  due  to  the  greater  flowing  of  the 
metal  on  these  faces  during  rolling.  Any  large  variation  in  the  distance 
between  the  rolls  from  end  to  end  shows  up  in  the  plate  at  once,  since  under 
such  conditions  it  will  curve  to  the  side  on  which  there  is  the  less  draught. 
If  the  variation  is  small  it  may  not  show  up  in  this  way.  The  plates  are 
gauged  four  times  daily  at  the  edges  and  in  the  middle  to  determine  the 
hollowness  and  variation.  Excessive  hollowness  is  corrected  by  putting  in 
a  new  middle  roll,  while  variations  are  overcome  by  inserting  or  removing 
liners  under  the  bearing  boxes.  During  the  rolling,  scale  is  removed  with 
salt  on  common  steels  or  with  burlap  and  coal  on  nickel  steel,  as  in  the 
rolling  of  slabs. 

Cooling  and  Straightening:  In  order  to  keep  the  cooling  of  plate 
uniform,  the  roll  tables  are  preferably  provided  with  collared,  or  disc  rolls 
instead  of  plain  ones,  which  cause  black  streaks  to  appear  across  the  plate. 
Disc  rollers  in  the  tilting  tables  of  the  mill  also  make  it  possible  to  roll 
very  narrow  slabs.  These  slabs  are  difficult  to  handle  on  plain  rolls,  because 
they  do  not  ride  these  rolls  in  a  horizontal  position,  but  tend  to  fall  down 
between  them  edgewise.  This  difficulty  is  overcome  with  the  disc  rollers, 
for  by  alternating  the  discs  the  bearing  surface  from  roll  to  roll  is  brought 
nearer  together  than  is  possible  with  plain  rolls,  and  there  is  no  straight 
line  of  separation  between  rollers.  After  the  rolling  is  completed,  the 
plate  is  passed  by  roll  tables  to  a  Hilles  &  Jones  cold  roll  straightener. 
This  straightener  is  constructed  of  two  rows,  one  above  the  other,  of  small 
rolls,  five  in  the  top  and  four  in  the  bottom  row.  The  centers  of  the  rolls 
in  the  top  and  bottom  rows  are  alternated,  so  that  the  piece,  on  entering 
between  the  rolls,  is  given  a  long  bend  or  sweep  which  is  then  removed  by 
smaller  sweeps  until  the  piece,  on  passing  out  of  the  rolls  is  quite  or  nearly 
straight.  Two  or  more  passes  may  be  required  to  straighten  some  plates. 
The  best  work  is  done  on  plates  about  one-half  inch  thick,  as  they  still 
retain  enough  heat  when  arriving  at  the  cold  rolls  to  be  well  and  easily 
straightened.  The  rolls  are  operated  by  motors,  and  the  draught  is  set  on 
the  mill  by  gears  connected  to  a  motor.  From  the  rolling  order  sheets,  the 
cold  roller  obtains  the  gauge  of  the  plate  when  finished  and  then  sets  the 
cold  rolls  to  take  a  plate  of  that  gauge. 

Laying=out  and  Stamping :  After  being  straightened,  the  plates  pass 
to  the  cooling  bed  and  then  to  the  marking  tables.  Here  the  heat  number, 
slab  number,  customer's  name,  or  mark,  and  plate  dimensions  are  written 
on  the  plate  by  the  marker.  The  plate  is  now  ready  to  be  laid  out  by  the 
gauger.  Laying  out  consists  of  drawing  out  in  chalk  the  plate  or  plates 
as  they  are  to  be  sheared,  it  being  remembered  that  the  plate  as  rolled 
from  a  slab  may  be  made  up  so  as  to  give  material  for  two  or  more  plates, 
in  which  case  the  plate  as  rolled  is  called  a  combination.  As  the  plates 


428  ROLLING  FINISHED  PRODUCTS 

are  still  hot  when  gauged,  allowance  must  be  made  for  shrinkage,  this 
allowance  amounting  to  one-fourth  inch  in  width  and  length  for  each  hundred 
inches  on  plates  up  to  one-fourth  inch  in  thickness,  and  three-eighth  inch 
for  each  hundred  inches  of  length  or  width  on  gauges  over  one-fourth  inch. 
This  difference  is  necessary  on  account  of  the  higher  finishing  temperature 
of  the  thicker  plates.  In  case  plates  come  to  the  marking  table  that  will 
not  make  the  plates  ordered,  on  account  of  being  too  short  or  too  narrow, 
the  material  must  either  be  applied  on  another  order  or  put  in  stock.  Any 
plates  with  objectionable  surface  defects  are  rejected  at  the  marking  table 
and  stocked.  Plates  stocked  at  the  table  are  treated  in  the  same  manner  as 
rejections,  although  they  are  not  listed  as  such,  because  they  have  not  been 
finished  at  the  time  of  stocking.  If  a  plate  has  a  snake  or  is  pitted  on  one 
end,  this  part  may  be  sheared  off  and  the  remainder  used  on  a  different 
order  than  that  for  which  it  was  intended.  Plates  that  are  too  narrow  to 
make  the  ordered  plates  are  held  until  an  order  can  be  found  calling  for  such  a 
gauge,  width  and  length  as  can  be  cut  from  them.  It  is  a  duty  of  the  stock 
marker  to  replace  such  plates  as  are  taken  from  the  marking  table.  A 
report  is  made  on  the  rolling  order  sheet,  by  the  marker,  of  the  number 
of  plates  made  on  an  order,  and  the  stock  marker  informs  the  office  of  all 
plates  made  from  stocked  material.  While  plates  are  being  laid  out  they 
are  stamped,  giving  heat  number  or  slab  number  as  is  desired,  and  any 
other  stamp  that  may  be  called  for  on  the  order  by  the  purchaser.  Heat 
number,  slab  number  and  size  is  also  painted  on  the  plates  with  white  lead 
after  they  are  marked.  Some  orders  require  that  heat  numbers,  etc.,  are 
to  be  painted  instead  of  being  stamped,  this  being  more  generally  the  case 
on  very  light  gauge  plates.  The  method  used  in  laying  out  a  plate  can  be 
described  from  sketches,  such  as  those  shown  in  Fig.  74. 

First,  the  width  of  the  plate  is  taken  at  AB  to  determine  the  amount 
of  stock  over  that  of  the  ordered  width  plus  allowance  for  shrinkage.  The 
stock  is  then  divided  so  as  to  give  one-half  to  each  side.  Point  C  is  set 
leaving  the  distance  BC  as  excess  stock.  Point  O  is  now  set  along  XY 
in  the  same  manner  as  point  C.  Line  CO  is  drawn  with  a  chalked  string 
or  a  straight  edge.  Widths  OM — EN — CP  and  others,  if  needed,  are 
measured  using  line  CO  as  a  base.  Line  PM  is  then  drawn  by  "the  line 
drawer."  A  right  angled  square  is  now  used  to  draw  line  CP  at  right 
angles  to  CO,  thus  squaring  up  the  plate.  The  true  length  of  the  plate 
is  taken  along  CO,  using  C  as  a  starting  point,  and  OM  is  likewise 
drawn  at  right  angles  to  CO. 

In  case  the  plate  is  curved,  the  base  lines  must  take  the  direction 
indicated  in  Sketch  II  in  order  to  avoid  scrap,  and  in  case  the  length  of 
the  plate  ordered  is  such  as  X'Y'  the  plate  cannot  be  made  on  account  of 
the  curve.  This  plate  must  be  applied  on  orders  that  require  lengths  of 
approximately  XI  and  QR,  with  widths  and  gauge  such  as  can  be  obtained 
on  the  given  plate.  Whenever  the  number  of  plates  ordered  to  the  same 


SHEARED  PLATES 


dimensions  will  justify  the  expense,  patterns  of  wood  are  made  for  laying 
out.     Sketch  plates  are  always  marked  out  to  a  templet,  or  pattern. 

Test  Pieces :  In  laying  out  the  plate  sufficient  material  must  be  given 
to  allow  for  the  test  pieces  that  are  required.  On  sheared  plates  both 
longitudinal  and  transverse  test  pieces  are  often  taken. 

Shearing:  Three  shears,  one  end  and  two  side  shears,  are  used  on  the 
one  hundred  forty  inch  mill,  and  are  so  arranged  that  the  plate  does  not 
require  turning  to  shear  the  sides.  The  ends  are  sheared  first,  and  the 


FIG.  74.     Sketches  Illustrating  the  Laying  Out  of  Plates. 


plate  is  then  passed  over  castors  to  the  side  shears.  This  mill  is  also 
equipped  with  a  rotary  shear  for  heads  and  other  circular  plates,  an  alligator 
shear  and  a  scrap  shear. 


430  ROLLING  FINISHED  PRODUCTS 


Shearing  Tolerances:  It  is  evident,  even  to  the  casual  observer,  that 
conditions  at  the  mills  are  such  that  shearing  to  exact  dimensions  is  imposs- 
ible. Observations  made  on  any  one  mill  will  reveal  many  of  these  un- 
favorable conditions  and  also  show  that  it  is  impossible  to  remedy  them. 
The  plates  must  be  sheared  in  the  order  they  are  rolled,  and,  to  keep  up 
with  the  mill,  rapid  working  is  required,  a  condition  that  makes  it  difficult 
to  lay  out  or  shear  accurately.  Owing  to  variations  in  the  thickness  of  the 
plates  and  in  the  time  required  for  rolling  them,  they  leave  the  cooling 
beds  at  widely  varying  temperatures.  Since  there  is  no  way  of  knowing 
accurately  just  what  this  temperature  is  at  the  time  of  laying  out  the  plate, 
proper  allowance  cannot  be  made  for  the  shrinkage,  the  total  amount  of 
which  will  also  vary  with  the  dimensions  of  the  plate.  Thus,  while  a  plate 
H  mch  thick  and  100  inches  long  may  require  an  allowance  of  ^  inch 
for  length,  a  plate  one  inch  thick  and  200  inches  long  may  require  an 
allowance  of  %  inch.  Finally,  since  no  mechanical  stops  can  be  used  on 
plate  shears,  the  plates  must  be  adjusted  to  position  under  the  shear  knife 
by  eye-and-hand  methods,  which  are  not  favorable  to  accurate  work.  Since 
the  conditions  in  the  different  mills,  such  as  length  and  type  of  cooling  bed, 
kind  of  material  rolled,  etc.,  vary  a  great  deal,  it  is  practically  impossible 
to  fix  standard  variations  covering  all  kinds  of  plates  that  will  be  just  to 
the  mills  and  the  consumers  alike.  In  justice  to  the  former  it  should  be 
stated  that  every  attempt  is  made  to  shear  as  near  to  the  exact  dimensions 
ordered  as  the  class  of  material  would  appear  to  call  for  and  the  mill 
conditions  will  permit. 

•Inspection  for  Size:  After  the  shearing,  all  plates  are  inspected  for 
size.  If  a  plate  does  not  measure  up  to  the  dimensions  ordered  or  to  within 
the  tolerances  permitted  by  the  order  department,  it  is  rejected  and  return- 
ed to  be  applied  on  another  order  calling  for  the  same  grade  of  material. 

Weighers :  All  plates  are  weighed  separately,  the  weight  and  number 
of  plates  made  being  recorded  on  a  copy  of  the  rolling  order  sheet  given 
to  the  weigher. 

Checkers :  The  checker  receives  a  copy  of  all  rolling  orders  and  checks 
each  item  for  size  and  pieces  ordered.  On  the  weigher's  copy  of  the  rolling 
.order,  he  lists  the  estimated  weight  of  the  plate  as  ordered  so  as  to  give 
the  weigher  the  ordered  weight,  who,  after  taking  the  actual  weight,  can 
determine  at  once  whether  the  plate  will  meet  the  specifications  as  to 
weight.  The  checker  lists  all  plates  ordered  in  the  order  book,  and  receives 
a  copy  of  all  orders  to  be  rolled  on  the  mill,  so  as  to  avoid  the  making  of 
duplicates  in  case  a  plate  is  ordered  twice.  In  case  error  is  found  in  dimen- 
sions of  plates  listed  OL  the  rolling  order,  the  checker  informs  the  roller 
and  marker.  The  checker  also  lists  all  plates  made  in  the  order  book, 
thus  keeping  a  record  of  the  plates  still  on  order. 


UNIVERSAL  MILL  PLATE  431 


Slip  Maker:  The  slip-maker's  duty  is  to  make  a  form  giving  the 
following  information:  mill,  slip  number,  customer's  name,  Carnegie  order 
number,  sheet  number  of  order,  heat  number,  number  pieces  made,  dimen- 
sions, marks  and  actual  weight.  The  dimensions,  etc.,  are  to  be  takenfrom 
the  plate,  formerly  painted  on  by  the  painter  at  the  marking  table.  A 
copy  of  the  rolling  order  is  at  the  disposal  of  the  slipmaker  to  aid  in  identi- 
fying plates,  but  data  cannot  be  taken  from  the  order  without  seeing  the 
marks  on  the  plate,  in  as  much  as  certain  plates  may,  at  the  marking  tables, 
be  applied  on  orders  different  from  those  they  were  originally  intended  for. 
A  new  or  separate  slip  is  made  out  for  each  order  number.  The  signature 
of  the  slipmaker  is  required  on  each  slip  for  identification. 

Recorder :  The  duty  of  the  recorder  is  to  test  the  weights  of  all  plates 
made  and  note  the  turn  on  which  they  were  rolled  and  sheared.  The 
record  here  taken  is  the  final  record  of  the  product  made  and  must  be 
taken  very  accurately.  Special  forms  are  used  for  recording,  showing  turn, 
numbers,  weight,  descriptions  of  plates,  etc.  Special  sheets  are  made  for 
alloy  steels  and  small  pieces  that  are  inspected  at  the  time  of  measuring 
for  size. 


SECTION   III. 

UNIVERSAL  MILL  PLATES. 

The  Forty-eight  Inch  Mill  at  Homestead  as  an  Example  of  Universal 
Plate  Mills:  This  mill  consists  of  two  horizontal  rolls  and  four  vertical 
rolls,  two  on  each  side  of  the  horizontal  ones,  all  contained  in  the  same 
housings  and  driven  by  the  same  engine.  This  construction  makes  the  mill 
a  very  complicated  piece  of  machinery,  a  detailed  description  of  which 
would  be  too  lengthy  to  attempt  here,  so  only  such  matters  as  are  necessary 
to  an  understanding  of  the  working  of  the  mill  will  be  discussed.  While  the 
working  surface  of  the  horizontal  rolls  is  only  four  feet,  which  is  the  same 
as  the  maximum  spread  of  the  vertical  rolls,  the  total  length  of  the  rolls 
is  thirteen  feet  one  inch,  of  which  length  twenty-four  inches  makes  up  the 
wobblers,  forty-five  inches  the  necks,  and  forty  inches,  twenty  inches  on 
each  side,  crosses  the  spaces  in  front  of  the  vertical  rolls,  which  must  stand 
between  the  housings.  These  rolls  are  connected  to  the  engine  and  are  driven 
in  the  same  way  as  the  ordinary  reversing  mill.  The  total  lift  of  the  hori- 
zontal rolls  is  twenty  inches.  The  screw  down  on  these  rolls  is  the  same 
as  that  on  the  sheared  plate  mill,  and  the  same  form  of  graduated  drum  is 
used  to  indicate  the  lift  of  the  rolls,  or  the  gauge  of  the  plate.  The  vertical 
rolls,  whose  centers  are  located  three  feet  one  inch  from  the  centers  of  the 
horizontal  rolls,  are  seventeen  and  one-half  inches  in  diameter  at  the  body, 
and  the  height  of  their  rolling  surface  is  two  feet  four  and  one-eighth  inches. 
They  are  provided  with  bearing  boxes  at  both  their  tops  and  bottoms.  A 
five  inch  collar  on  the  upper  end  of  the  lower  neck  rides  on  a  side  bearing 


432  ROLLING  FINISHED  PRODUCTS 

in  the  bottom  box  which  furnishes  the  vertical  support  for  the  roll.  A 
screw,  bearing  on  a  frame  attached  to  the  bearing  boxes  and  actuated  by 
an  electric  motor,  furnishes  the  means  by  which  the  pressure  for  rolling  is 
applied  to  these  rolls;  for  spreading  them  hydraulic  jacks  are  used.  Large 
discs,  graduated  on  their  circumferences  and  mounted  on  the  screws,  indicate 
the  spread  of  the  vertical  rolls.  As  already  stated,  these  rolls  are  driven 
through  a  system  of  gears  by  the  same  engine  that  drives  the  horizontal 
rolls.  Beginning  with  the  engine,  the  power  is  transmitted  to  the  horizontal 
rolls  in  the  usual  manner  for  reversing  mills,  while  the  drive  for  the  vertical 
rolls  is  taken  off  the  upper  pinion.  Upon  the  prolongation  of  the  outside 
bearing  of  this  pinion,  a  second  gear  is  keyed.  This  gear  meshes  with  two 
idlers,  one  on  either  side,  which  in  turn  mesh  with  gears  mounted  on  the 
ends  of  the  two  drive  shafts  for  the  vertical  rolls.  These  shafts  then  extend 
to  and  across  the  roll  housings,  where  they  are  supported  by  suitable  bear- 
ings. On  the  section  of  these  shafts  included  between  the  roll  housings  are 
mounted  four  sliding  miter  gears  which  mesh  into  similar  crown  gears  keyed 
to  the  tops  of  the  rolls.  Through  these  gears  the  peripheral  speed  of  the 
vertical  rolls  is  adjusted  to  equal  the  speed  of  the  horizontal  rolls,  and 
never  more.  Hence,  the  vertical  rolls  may  be  used  on  the  piece  only  on 
the  entering  side  of  the  passes,  because  if  the  vertical  rolls  were  used  on 
the  delivery  of  the  plate  the  greater  speed  of  the  piece  due  to  the  elongation 
produced  by  the  horizontal  rolls  would  jam  the  material  between  the  two 
sets  of  rolls.  The  rolling  of  the  piece  on  the  entering  side  is  preferable  to 
rolling  on  the  delivery  side,  as  then  thin  plates  would  tend  to  buckle  or 
bow  up  in  the  center  on  applying  pressure  from  the  vertical  rolls.  These 
rolls  cannot  be  brought  closer  together  than  twenty  inches.  Hence,  the 
mill  has  a  range  in  width  of  plates  from  twenty  to  forty-six  inches. 

The  Operation  of  Rolling:  Rolling  universal  mill  plates  involves 
most  of  the  difficulties  of  rolling  sheared  plates,  and  in  addition  there  are 
several  features,  due  to  the  vertical  rolls,  that  are  not  peculiar  to  sheared 
plate  mills.  Thus  the  piece  must  always  enter  the  mill  at  right  ang]  es  to  the 
horizontal  rolls,  as  otherwise  the  action  of  the  vertical  rolls  will  cause  the 
plate  to  buckle  or  curl  or  jam  between  the  rolls.  As  the  plates  rolled  on 
this  mill  are  in  very  long  lengths,  the  slightest  variation  in  the  spacing  of  the 
horizontal  rolls  shows  up  as  a  decided  camber  in  the  plate  as  it  runs  out 
on  the  table.  To  correct  this  defect,  which  is  prone  to  occur  on  universal 
mills,  a  spanner  block  is  placed  under  the  screw  down  on  the  roller's  side 
of  the  mill.  By  means  of  a  spanner  bar  and  a  sledge  hammer,  this  block 
may  be  turned  and  the  proper  adjustment  made  on  this  end  of  the  upper 
horizontal  roll  to  cause  the  plate  to  roll  straight.  As  to  the  draught  and 
manipulation  of  the  horizontal  rolls,  the  plate  is  reduced  in  the  same  way 
as  on  the  sheared  plate  mill.  On  the  vertical  rolls  the  greatest  draughts 
are  taken  in  the  first  few  passes,  the  object  being  to  reduce  the  piece  to 
the  desired  width  as  quickly  as  possible,  after  which  the  pressure  on  the 
vertical  rolls  is  just  sufficient  to  hold  the  piece  to  width.  This  mill  rolls 


UNIVERSAL  MILL  PLATE  433 

many  plates  directly  from  the  ingot.  Ingots  intended  for  this  purpose  are 
rectangular  in  section,  beijig  from  one  to  two  inches  wider  at  the  smaller 
end  than  the  width  of  the  plate  desired.  In  beginning  the  rolling  of  these 
slab  ingots  the  rollers  prefer  to  have  the  small  end  enter  the  mill  first,  as 
in  this  way  the  suddenness  of  the  pull  on  the  mill  is  avoided  and  the  draught 
can  be  more  easily  adjusted,  but  many  plates  are  rolled  with  the  butt  end 
of  the  ingot  entering  first.  The  chief  objection  to  rolling  plates  directly 
from  ingots  is  that  the  pipe  and  central  line  of  segregation  is  rolled  into 
the  plate,  and  in  order  to  avoid  it  the  scrapping  of  a  large  amount  of 
finished  material  is  necessary. 

Straightening.  Marking  and  Shearing  U.  M.  Plate:  From  the  rolls, 
the  plate  is  carried  on  live  roller  tables  to  the  two  cooling  beds,  which 
extend  in  opposite  directions  from  both  sides  of  the  receiving  table.  Here 
any  curve  or  camber  is  removed  from  the  plates  by  clamping  them  tightly 
to  a  straight  edge.  The  buckles  thus  produced  on  the  edges  of  the  plate 
are  then  flattened  out  with  wooden  mallets.  While  the  mill  is  provided 
with  a  machine  straightener,  similar  to  the  one  employed  at  the  one  hundred 
forty  inch  mill,  it  is  seldom  used,  the  general  practice  at  universal  plate 
mills  being  to  straighten  the  plates  in  the  manner  described  above.  Every 
plate  rolled  on  this  mill  has  the  name  and  letters  "Carnegie,  U.  S.  A." 
rolled  into  it  at  intervening  spaces  of  seven  feet.  While  on  the  cooling  beds 
the  plates  are  marked  off  for  length,  the  heat  number  is  stamped  on,  and 
the  slab  number,  size  of  plate,  order  number  and  the  customer's  name  is 
marked  on  with  white  paint.  The  plates  then  move  on  to  the  receiving 
tables,  which  carry  them  to  shears,  where  the  plates  are  cut  to  length.  A 
large  shear  used  for  splitting  plates  is  also  provided.  Unless  otherwise 
specified,  two  longitudinal  tests  for  the  physical  laboratory  are  taken  for 
each  order  or  on  each  heat  of  steel;  one  test  is  taken  from  the  top  of  the 
ingot,  and  the  other  from  the  bottom.  The  weighing,  recording,  and  in- 
spection of  the  plates  are  then  conducted  as  for  sheared  plates. 

Advantages  of  Universal  Mill  Plates:  While  the  effect  of  the  one 
way  rolling  on  Universal  mill  plates,  as  will  be  explained  shortly,  is  such 
as  to  require  care  and  discrimination  in  their  use,  they,  nevertheless, 
possess  certain  advantages  over  sheared  plates  that  make  them  more 
desirable  for  some  purposes.  First,  the  possibility  of  producing  plates  of 
great  length  with  a  rolled  edge  makes  them  available  for  many  purposes, 
such  as  girder  construction,  for  which  sheared  plates  are  not  suitable. 
Second,  the  ability  to  roll  to  fairly  exact  widths  reduces  shearing  costs  to 
a  minimum.  Third,  the  rolled  edge  eliminates  all  costs  to  the  purchaser 
for  machining.  As  a  fourth  advantage  the  greater  tonnages  that  these 
mills  are  capable  of  producing  may  be  cited,  because  this  tends  to  keep  the 
first  cost  to  the  customer  low. 

Physical  Properties  of  Plates :  The  effect  of  rolling  on  the  physical 
properties  of  steel  is  now  generally  recognized  by  the  users  of  plates,  and 


434  ROLLING  FINISHED  PRODUCTS 


specifications  are  usually  written  accordingly.  In  a  previous  discussion  of 
this  subject  it  was  -made  plain  that  the  controlling  factors  during  rolling 
are  the  amount  of  work  done  and  the  temperature  above  the  critical  at 
which  the  rolling  is  completed.  To  these  there  should  now  be  added  the 
manner  in  which  the  rolling  is  performed.  Attention  has  been  called  to 
the  different  methods  of  rolling  plates  in  the  preceding  description.  It 
will  be  recalled  that  the  plate  may  be  rolled  from  the  slab  with  one  reheating 
or  from  the  ingot  direct  without  reheating.  As  to  the  difference  in  effect 
produced  by  these  two  methods,  there  is  little  data  on  the  subject,  but 
reasoning  from  the  theoretical  standpoint,  there  should  be  no  difference. 
The  abandonment  of  the  method  of  rolling  from  the  ingot  is  probably  due 
to  economic  considerations  rather  than  to  any  tendency  of  the  method  to 
produce  defective  material.  Again,  in  the  rolling  of  the  slab  or  ingot  it 
was  pointed  out  that  all  the  rolling  may  be  in  one  direction  only,  or  the 
plate  may  be  rolled  both  transversely  and  longitudinally.  Here  a  marked 
difference  is  observed  to  result  from  the  two  methods  of  rolling.  For 
example,  if  a  slab  or  ingot  be  rolled  in  one  direction  only  and  a  longitudinal 
and  transverse  test  piece  be  cut  from  the  resulting  plate,  little  difference 
in  tensile  strength  will  be  observed  in  pulling  the  two  tests,  but  a  marked 
difference  in  ductility  will  be  found.  Thus,  the  longitudinal  piece  will  give 
from  4%  to  7%  greater  elongation  than  the  transverse  piece,  and  10%  to 
15%  greater  reduction  in  area.  Concerning  the  amount  of  work  and  finish- 
ing temperature,  the  ductility  is  affected  in  a  somewhat  erratic  way, 
while  the  tensile  strength  is  increased  by  increased  work  and  lower 
finishing  temperatures.  Thus,  a  thin  plate  will  show  a  very  appreciable 
increase  in  tensile  strength  over  a  thick  one  rolled  from  the  same 
slab  or  «  ingot,  and  to  obtain  the  same  strength  in  plates  of 
different  thicknesses  it  is  necessary  to  employ  chemical  control.  The 
following  table  is  intended  to  show  approximately  the  variations  in  the 
carbon  content,  other  metalloids  being  constant,  that  should  be  made  to 
produce  plates  of  uniform  strength  when  varying  in  thickness  as  indicated. 

Table  57.    Showing  Variation  of  Carbon  Content  with  the  Thickness 
of  Plates  to  Give  the  Same  Strength. 

THICKNESS  CARBON 

OF  PLATE  REQUIRED 

%" - 12% 

Jie" 15% 

W - - 17% 

M"~- - 18% 

1" 19% 

1W - - --.20% 

Inspection  of  Plates  for  size  and  weight  is  made  by  mill  inspectors, 
while  inspection  for  surface  and  other  defects  are  made  either  by  mill  or 
customer's  inspectors.  Certain  surface  defects,  as  snakes  and  surface 


DEFECTS  IN  PLATES 


435 


marks,  may  do  the  plate  no  harm  if  they  do  not  extend  too  deep  into  the 
metal,  and  may  be  ground  out  with  any  suitable-  device.  For  this  purpose 
a  movable  electrical  grinding  wheel  is  employed.  The  rigidness  of 
the  inspection  may  be  surmised  from  a  glance  at  the  inspector's  list  of  causes 
for  rejection,  which  is  here  appended.  Most  of  these  reasons  are  self- 
explanatory,  while  others  have  already  been  discussed,  so  that  no  further 
explanation  is  required. 

Table  58.     Defects  for  Which  Plates  are  Rejected. 

DEFECTS  ACQUIRED  OR  CAUSED  FROM 


THE 
INGOT 

IN 
HEATING 

IN 
ROLLING 

IN  LAYING 
OUT 

IN 

SHEARING 

FROM  MANY 
SOURCES 

Blister 

Burnt 

Split 

Wrong 

Scant 

Snake 

Pipe 

Bricked 

Slivers 

Dimen- 

Bad Edge 

Seams 

Slivers 

Scabby 

Dished 

sions 

Crop  end 

Test  lost 

Seams 

Cinder  spot 

Pitted 

Made 

Test  piece 

Duplicate 

Scored 

wrong 

cut 

Broken 

Buckled 

Knifed 

Ground 

Over 

too  deep 

weight 

Cracked 

Under 

Tests  are 

weight 

not  within 

Over  and 

specifica- 

under 

tion 

gauge 

Scale 

Cambered 

Laminated 

Roll 

marked 

Bad  edge 

(Universal 

Mill 

Plates 

only) 

436  THE  ROLLING  OF  SECTIONS 


CHAPTER  VIII. 

THE  ROLLING  OF  LARGE  SECTIONS. 

SECTION   I. 

RAILROAD    RAILS. 

Development  of  Rail  Manufacture:  Dating  from  the  invention  of 
the  steam  locomotive,  the  railroad  rail  represents  one  of  the  first  sections 
with  which  the  rolling  mill  operators  had  to  deal,  as  well  as  one  of  the 
most  difficult  and  certainly  the  most  important.  The  importance  of  the 
railroad  as  a  factor  in  modern  civilization  and  progress  is  recognized  by 
all,  and  that  the  rail  is  a  most  vital  part  in  railroad  operations  is  just 
as  evident.  With  the  advancement  in  speed  of  travel  and  weight  of 
loads  carried,  more  and  more  has  been  required  of  the  rail,  until  to-day 
no  material  is  subjected  to  more  severe  punishment  in  service  than  the  rail- 
road rail.  Exposed  to  the  weather  at  all  times,  it  is  subjected,  under 
constantly  varying  conditions,  to  immense  compression  and  bending  stresses, 
shocks,  vibrations,  friction  and  wear.  The  form  of  the  rail,*  then,  should 
be  such  as  will  give  the  greatest  transverse  strength,  provide  abundance 
of  metal  for  wear,  present  a  wide  base  for  fastening  to  the  cross  tie,  and 
still,  for  the  sake  of  economy,  be  of  the  lightest  section  possible.  Now,  it 
so  happens,  that  the  form  that  best  meets  all  these  requirements  is  the 
section  known  as  the  American  Tee  Rail.  It  also  happens  that  this  section 
was,  in  the  early  days  of  rolling  mills,  one  of  the  most  difficult  sections 
to  roll,  mainly  on  account  of  the  wide  flange.  The  history  of  rail  develop- 
ment as  indicated  in  the  sketches  of  Fig.  75  gives  evidence  of  this  fact. 

Thus,  the  first  real  departure  made  from  the  original  strap  rail  of  1808 
was  the  chair  rail  of  1820.  As  the  chair  of  this  rail  was  expensive,  an  attempt 
was  made  in  the  section  of  1831  to  roll  a  rail  with  a  wide  and  relatively 
heavy  flange  on  the  bottom  to  replace  this  chair.  The  difficulty  of  rolling 
the  flange  led  to  the  better  balanced  bull  head  of  1837,  the  U-shape  of  1844 
and  the  pear  head  rail  of  1845.  Then  came  the  compound  rail  of  1856  and 
the  form  of  1860,  which  is  the  U-shape  of  1844  with  the  lower  parts  closed 
in  and  welded  to  form  the  web.  As  neither  of  these  forms  proved  service- 
able, a  demand  for  more  metal  in  the  head  for  wear  forced  a  final  return 
in  1865-8  to  the  tee  shape  with  wide  thin  flange.  From  this  date  the  design 
of  rolls,  quality  of  material,  and  lay-out  of  the  mills  has  gradually  been 
improved  until  at  the  present  time  the  American  rail  mills  are  not  only 
producing  the  largest  tonnage  of  the  world  but  also  rails  of  the  best  possible 
grade. 


RAILS 


437 


Methods  of  Rolling  Rails:  Rails  were  originally  rolled  on  the  pull- 
over mill,  and  then  on  the  reversing  mill,  which  in  England  is  the  type 
of  mill  still  employed  for  this  purpose.  But  in  this  country  all  rails  are 
rolled  on  the  three-high  mill,  which  formerly  was  usually  made  up  of  a  single 
train  of  three  stands  driven  with  one  engine.  With  the  increase  in  the  size  of 
the  section,  which  has  almost  doubled  in  weight  within  the  last  quarter* 
century,  and  the  growing  demand  for  larger  quantities  and  better  quality 
in  the  product,  a  more  advantageous  lay-out  of  the  mills  for  handling  this 


1808  1820 

Strap  Rail    Birkenshaw  Chair  Rail 
19  Ibs.  per  yd.        25.8  Ibs.  per  yd. 


1830 

Clarence  Chair  Rail 
33  Ibs.  per  yd. 


1831  1837 

Stevens',  (the  1st.  T-rail)  Lock's  (BullHead) 
40.8  Ibs.  per  yd.        Rail,  58  Ibs.  per  yd 


1844 

Evans' 40  Ib.U-Rail 

First  Rail  Rolled  in 

United  States. 


1845 

58  Ib.  Pear  Head 

Rail,  First  T-rail 

Rolled  in  U.  S. 


1856 

Compound  Type  of 
Rail,  60  Ibs.  per  yd. 


1858 

P.  R.  R.  Standard 
85  Ibs.  per  yd. 


1883  1892 

P.  H.  Dudley  Design    P.  R.  R.  Standard 

80.2  Ibs.  per  yd.          100  Ibs.  per  yd. 


1910 

C.  R.  R.  of  N.  J. 
135  Ibs.  per  yd. 


1868  1874 

Welch  Design        Chanute  Design 
67  Ibs.  per  yd.        60.3  Ibs.  per  yd. 
First  Bess,  Rail 
Rolled  in  U.  S. 
(1865)    similar 

to  this 

Fia.  75.     Sketches  of  Rail  Sections  Illustrating  the  Evolution  of  the   Railroad  Rail 
in  America. 


material  became  necessary.  The  more  modern  rail  mills  wilt,  therefore, 
consist  of  two  or  three  trains,  each  separately  driven  and  made  up  of  one 
or  more  stands  of  rolls,  all  so  arranged  that  the  rolling  of  the  piece  in  any 
one  stand  is  complete  before  it  is  passed  to  the  next  succeeding  one.  With 
this  arrangement  the  output  of  the  mill  is  greatly  increased  without  much 
increase  in  the  speed  of  the  rolls,  because  different  pieces  may  be  rolling 
at  different  stages  at  the  same  time,  and  the  turning  of  the  piece  between 
passes  is  avoided.  As  to  the  heating  of  the  steel,  rails  may,  as  previously 


438  THE  ROLLING  OF  SECTIONS 


stated,  be  rolled  either  from  blooms  that  have  been  reheated  after  having 
been  rolled  from  the  ingot,  or  on  the  original  heat  of  the  ingot.  The  latter 
method,  which  was  introduced  a  few  years  ago  mainly  to  save  the  extra 
cost  of  reheating,  was  until  very  recently  looked  upon  with  favor  both  by 
the  manufacturer  and  the  consumer,  who  believed  that  the  scheme  would 
have  a  beneficial  effect  upon  the  quality  of  rail  produced,  due  to  the  fact 
that  the  material  was  necessarily  finished  at  a  low  temperature.  Within 
the  last  two  years,  however,  sentiment  appears  to  have  taken  a  swing  in 
favor  of  reheating,  because,  as  is  claimed  by  the  advocates  of  reheating, 
the  increased  speed  of  rolling  combined  with  the  heavy  draughts  required 
to  complete  the  rolling  on  the  original  heat  is  liable  to  produce  a  condition 
favorable  to  the  formation  of  fractures.  The  effects  of  too  rapid  reduction 
have  already  been  discussed.  For  the  same  reason  the  temperature  of  th6 
ingot  is  kept  high,  which  fact  increases  the  danger  of  overheating.  In 
addition,  the  difficulty  of  keeping  the  finishing  temperature  constant,  pre- 
sents a  serious  problem.  On  the  other  hand,  by  reheating  the  bloom  the 
two  initial  rolling  temperatures  may  be  lower  and  be  kept  more  uniform, 
and  the  shaping  of  the  rail  may  progress  more  leisurely.  As  to  the  manner 
of  forming  the  section,  there  are  two  methods  of  rolling,  known  as  the  flat, 
or  slab-and-edging,  and  the  diagonal,  or  angular,  method.  To  impart  even 
a  slight  understanding  of  these  methods  requires  a  lengthy  explanation; 
•but  in  the  proper  design  of  the  various  passes  for  the  progressive  forming 
of  the  rail,  as  for  any  section,  lies  the  crux  of  the  rolling  process.  Therefore, 
as  the  subject  is  one  of  great  interest,  an  attempt  is  to  be  made  to  discuss 
the  matter  in  as  brief  and  comprehensive  a  manner  as  possible  under  the 
headings  that  follow. 

How  to  Study  Roll  Design :  The  best  way  to  explain  roll  design  is 
by  an  example,  for  it  is  as  yet  an  art  acquired  mainly  by  experience.  While 
subject  to  natural  laws,  the  scientific  aspects  of  the  subject  have  not  been 
fully  developed,  and  the  roll  designer  has  few  rules  to  learn.  This  con- 
dition tends  toward  individuality  in  designing,  with  the  result  that  it  is 
seldom  two  designers  will  be  found  to  do  the  same  thing  in  the  same  way. 
To  serve  as  such  an  example  the  flat  method  of  rolling  as  carried  out  at 
the  Edgar  Thomson  Works  will  be  described,  because,  of  the  two  methods 
of  rolling,  this  is  the  older  and  the  one  more  generally  employed.  Before 
beginning  with  the  example,  however,  some  preliminary  explanations  are 
required. 

Precautions  to  be  Observed  in  Designing  the  Rolls:  Of  course  the 
first  consideration  in  roll  designing  is  to  produce  a  finished  piece  of  the 
correct  size  and  form,  and  this  must  be  done  by  spreading,  bending  and 
directing  the  flow  of  the  steel.  The  ease  with  which  this  forming  is  done 
depends  on  the  plasticity  of  the  metal,  which  in  turn  is  affected  by  the  kind 
of  steel,  whether  open-hearth  or  Bessemer;  the  grade,  whether  high  or  low 
carbon;  and  the  temperature.  With  the  speed  of  the  rolls  fixed,  the  tem- 
perature confined  to  a  very  narrow  range,  and  the  kind  and  grade  of  steel 


RAILS  439 


given,  the  only  instrumentality  remaining  in  the  hands  of  the  roll  designer 
is  the  size  and  shape  of  the  passes,  and  in  part  of  these,  at  least,  the  size 
will  be  governed  by  the  size  of. the  bloom.  In  designing  the  passes,  a  good 
designer  will  endeavor  to  work  the  steel  in  such  a  manner  that  the  quality 
of  the  product  will  be  benefited,  and  no  defects  will  be  developed.  The 
defects  that  require  constant  care  are  fins,  laps,  overfills  and  underfills 
Laps  may  result  from  fins  or  a  collaring  of  the  piece  in  the  rolls;  overfills, 
from  worn  rolls,  bad  or  improper  design;  and  underfills  either  from  bad 
design  or  incorrect  adjustment  of  the  rolls. 

Stages  of  Reduction:  The  formation  of  the  rail  from  the  bloom  may 
be  looked  upon  as  taking  place  in  three  steps  or  stages.  The  first  stage, 
called  the  roughing,  is  merely  one  of  preparation;  in  it  a  large  amount  of 
work  is  done,  but  this  work  is  expended  mainly  in  reducing  the  size  of  the 
section  and  elongating  the  piece.  At  the  Edgar  Thomson  Works  the  piece 
is  reduced  in  seven  to  nine  roughing  passes.  In  the  first  four  to  six  passes, 
rolling  by  the  slab-and-edging  method,  the  section  retains  the  rectangular 
shape,  while  in  the  next  three  passes  a  little  shaping  of  the  flange  is  begun 
to  prepare  the  piece  for  the  first  finishers,  in  which  there  are  five  passes. 
These  passes  are  given  names  in  order,  indicative  of  the  nature  of  the  work 
they  are  intended  to  perform,  as  follows:  slabber,  first  former,  second 
former,  third  former,  and  the  leader.  The  leader  is  the  pass  just  previous 
to  the  finishing  pass,  which  is  located  in  a  separately  driven  stand  of  two- 
high  rolls.  With  this  explanation  of  terms  used,  the  different  steps  in  the 
design  of  the  rolls  and  the  rolling  may  now  be  traced.  They  are  as  follows: 

The  Section:  No  original  designing  of  section  is  done  by  the  roll 
designer.  The  first  requirement  in  the  rolling  of  a  new  section  is,  then,  that 
the  roll  turner  be  supplied  with  a  drawing  or  print  of  the  section,  which 
must  be  accompanied  with  all  the  dimensions,  preferably  indicated  on  the 
print.  The  weight  of  rail  desired  or  expected  should  also  be  given.  Here 
the  matter  of  dimensions  is  of  extreme  importance,  for  the  designing  of  the 
templets  cannot  be  started  until  each  and  every  dimension  required  is 
given.  These  dimensions  not  only  include  linear  measurements,  such  as 
height  of  rail,  width  and  thickness  of  parts,  but  radii  of  all  curves,  and 
amount  of  slope  on  inclined  surfaces  expressed  in  degrees  or  percentages. 

The  Cold  Templet:  With  all  the  necessary  information  before  him, 
the  first  step  taken  by  the  roll  designer  is  to  prepare  a  drawing  for  the 
cold  templet.  This  templet  is  made  of  brass  and  represents  an  exact  section 
of  the  rail  when  cold.  This  drawing  is  constructed  on  the  axis  of  symmetry 
of  the  rail,  which  is  the  vertical  line  drawn  through  the  center  of  the  head, 
of  the  web,  and  of  the  flange.  On  this  line  the  section  of  rail  is  symmetrically 
constructed  to  the  dimensions  given  on  the  drawing,  all  the  dimensions 
being  made  with  extreme  care  and  accuracy.  All  measurements  are  made 
with  micrometers  or  steel  rules.  If  a  rule  is  used  a  magnifying  glass  is 
employed  to  take  the  readings.  The  construction  lines  are  made  as  fine  as 
possible.  Even  the  contraction  and  expansion  of  the  drawing  paper,  due  to 


440 


THE  ROLLING  OF  SECTIONS 


the  varying  humidity  of  the  atmosphere,  is  taken  into  consideration,  and 
the  proper  allowances  are  made.  With  this  very  accurate  drawing  com- 
pleted, the  area  of  the  section  is  measured  with  a  planimeter  in  order  to 
check  up  the  weight  of  the  section. If  this  weight  should  differ  from  that 
given  on  the  original  print  or  drawing,  the  templet  drawing  is  checked  and, 
if  correct,  the  customer  is  notified  that  the  actual  weight  will  not  be  as 
specified.  No  further  work  may  then  be  done  till  this  question  of  weight 
is  settled,  when  the  brass  templet  will  be  made  from  the  drawing. 


PASS 

HEAD 

WEB 

BASE 

TOTAL 

%RED. 

SPREAD 

FINISHING 

14.4 

5  4 

12.1 

31.9 

5% 

H" 

LEADER 

15.2 

5.7 

12.7 

33.6 

15% 

&" 

3RD  FORM. 

17.9 

6.7 

14.9 

39.5 

20% 

A" 

2nd  FORM. 

22.4 

8.4 

18.6 

49.4 

24% 

&" 

IST  FORM. 

29.5 

11.1 

24.3 

64.9 

22% 

&" 

SLABBER 

37.8 

14  2 

31.2 

83.2 

,  Reduction  in  Passes. 


FIG.  76.     Pass   Template    Drawing — Slab-and-Edging 
Method  of  Rolling  Rails. 


No. 

Pass 

%  Red. 

A 
B 

Finishing  Pass 
Leader 

5.   % 
15.   % 

C 

3rd.  Forming 

20.   % 

D 

2nd.  Forming 

24.   % 

E 

1st.  Forming 

22.   % 

F 

Slabber 

23.   % 

G 

9th.  Pass 

24.5% 

H 

8th. 

24.5  % 

I 

7th. 

22.   % 

J 

6th. 

27.   % 

K 

5th. 

22.8% 

L 

4th. 

17.7% 

M 

3rd. 

28.8% 

N 

2nd. 

17.   % 

0 

1st.     " 

14.5% 

P 

Bloom 

ROLL  DESIGN  FOR  RAILS  441 


The  Hot  Templet:  The  next  step,  which  is  really  the  first  step  in 
designing  the  roll  passes,  is  the  making  of  the  hot  templet.  This  templet 
is  exactly  like  the  cold  templet,  but  larger  in  size  to  allow  for  contraction, 
as  it  represents  the  section  of  the  rail  at  the  finishing  temperature  of  rolling. 
The  co-efficient  of  contraction,  or  exact  amount  to  allow  here,  is  determined 
by  experience.  From  this  hot  templet  the  various  passes  are  designed 
successively  as  the  experience  and  judgment  of  the  designer  dictates. 

The  Pass  Templet:  In  designing  these  templets,  the  designer  con- 
structs each  in  a  drawing  showing  the  different  passes  superimposed  upon 
each  other  as  in  the  accompanying  illustration.  In  actual  practice  these 
drawings  are  constructed  full  size,  but  for  convenience  in  printing  this 
photograph  is  three-eighths  natural  size.  This  illustration  represents  the 
passes  for  a  light  rail  rolled  by  the  slab-and-edging  method.  In  this  method, 
the  axis  of  symmetry  of  the  rail  coincides  with  the  pitch  line  and  is  parallel 
to  the  train  line  of  the  rolls,  as  can  be  seen  from  the  print.  The  more  darkly 
shaded  area  in  the  photograph  represents  the  hot  templet,  with  the  pitch  line 
or  axis  of  symmetry  drawn  through  it,  and  from  it  the  grooves  in  the  finishing 
pass  are  cut.  From  this  pass  the  roll  designer  works  back  to  the  bloom. 
As  a  preliminary  step  toward  designing  these  passes,  a  table  like  that  shown 
attached  to  the  photograph  is  prepared.  In  a  vertical  column,  headed  pass, 
are  placed  the  names  of  the  various  passes  from  slabber  to  finishing,  while 
the  figures  in  the  columns  designated  as  head,  web,  and  base  represent 
the  sectional  area  of  the  different  passes  for  these  parts  expressed  in  pounds 
per  yard,  which  is  directly  proportional  to  the  area  in  square  inches.  This 
table  is  prepared  as  follows:  The  areas  of  the  different  parts  of  the  rail 
are  fixed  by  the  hot  templet.  In  this  section  the  metal  was  proportioned 
in  the  design  so  as  to  give  14.4  pounds  per  yard  in  the  head,  5.4  pounds 
per  yard  in  the  web  and  12.1  pounds  per  yard  in  the  flange,  the  total  being 
31.9  pounds  per  yard,  which  is  heavier  than  the  cold  section  by  1.4  pounds 
per  yard.  This  difference  is  due  to  the  fact  that  the  weight  of  the  hot 
section  is  calculated  as  if  it  were  cold,  a  correction  for  difference  in  gravity 
not  being  necessary  for  this  purpose.  Next  will  be  put  down  under  the 
column  headed  per  cent,  reduction,  the  amount  of  reduction  expressed  in 
per  cent.,  which  from  experience  and  judgment,  the  designer  thinks  will 
be  best.  In  this  case  these  amounts  are  as  follows:  In  the  finishing  pass 
one-thirty-second  of  an  inch  reduction  on  each  side  of  the  web  is  allowed 
for  the  marking;  in  the  leader,  15%;  in  the  third  former,  20%;  in  the  second 
former,  24%;  in  the  first  former,  22%;  and  in  the  slabber,  23%.  From  these 
figures  the  areas  of  the  different  parts  of  each  pass  are  calculated,  and  the 
blanks  in  the  table  filled  in  as  shown.  Next,  the  amount  to  allow  for  spread 
of  the  piece  from  one  pass  to  the  other  is  decided  upon  and  placed  in  the 
column  headed  spread.  This  allowance  is  expressed  in  fractions  of  an  inch 
and  is  measured  and  allowed  for  along  the  axis  of  symmetry  as  shown  by 
the  positions  of  the  rail  heads  in  the  photograph.  With  the  reduction  for 
the  various  passes  and  their  parts  thus  apportioned,  the  designer  then  pro- 


442 


THE  ROLLING  OF  SECTIONS 


ceeds  to  draw  in  the  passes,  as  designated  in  the  photograph  by  the  letters 
a  to  p,  and  in  doing  so  he  keeps  the  following  points  constantly  in  mind. 
First,  is  the  danger  of  forming  fins.  As  an  aid  in  avoiding  these  defects  the 


FIG.  77.     Showing  Difference  in  Peripheral  Speed  of  the  Bolls  at  Web,  Head,  and 
Flange. 

piece  is  passed  through  the  mill  so  that  each  side  of  the  pass  alternately  enters 
an  open  and  closed  side  of  the  groove.  How  this  is  done  on  the  three-high 
mill  without  turning  the  piece  can  be  seen  from  a  study  of  Fig.  78.  Even 


ROLL  DESIGN  FOR  RAILS  443 


with  this  arrangement  fins  would  still  be  formed  if  the  passes  were  not 
properly  designed.  To  avoid  all  danger  of  fins  two  tricks  of  design  are 
here  resorted  to.  Thus,  in  the  leader,  or  pass  a,  the  corner  of  the  head, 
which  is  to  come  opposite  the  openings  between  the  rolls  in  the  finishing 
pass,  is  well  rounded  off,  so  that  the  spread  or  flow  of  the  metal  will  be 
taken  up  in  filling  out  this  rounded  corner  and  none  will  remain  to  be  forced 
into  the  clearance.  For  the  same  reason,  that  half  of  the  flange  on  the 
same  side  of  the  rail  is  left  much  shorter.  It  will  be  observed  that  this 
provision  is  made  in  all  the  passes  down  to  the  slabber.  From  the  photo- 
graph it  will  be  noticed  that  most  of  the  work  from  the  slabber  is  done 
along  the  fishing  of  the  rail,  the  metal  being  forced  horizontally  from  the 
central  portion  of  the  slab  toward  the  head  and  flange  and  vertically  into 
the  web.  This  is  done  by  holding  the  working  surface  under  the  head 
and  on  top  of  the  flange  at  the  angles  shown.  In  designing  this  part  of 
these  passes  care  must  be  taken  to  see  that  the  line  XY  at  the  bottom 
of  pass  d,  for  example,  is  not  greater  than  X'Y'  at  the  top  of  its  preceding 
pass  c,  as  otherwise  the  piece  would  be  collared  when  it  entered  d.  Great 
care  is  necessary  in  distributing  the  reduction  of  each  part  to  prevent  the 
metal  flowing  away  from  parts  where  it  is  needed.  Thus,  for  example,  if 
a  too  great  reduction  in  the  web  takes  place  in  one  pass,  it  will  produce  a  flow 
of  metal  away  from  the  head,  causing  the  latter  to  be  underfilled.  The 
cause  for  much  of  the  trouble  of  this  kind  lies  in  the  different  diameters 
of  the  pass,  which  causes  a  different  roll  speed  for  head,  webandflange, 
and  hence  different  rates  of  elongation.  If  the  elongation  at  one  point  due 
to  increased  speed  of  the  rolls,  is  not  balanced  by  elongation  produced  through 
compression  at  the  point  of  less  speed,  the  section  will  be  imperfectly 
formed,  or  cracks  will  result.  The  accompanying  illustration  (Fig.  77)  will 
help  in  understanding  this  point.  In  all  reduction,  it  is  a  good  plan  to  keep 
the  angle  of  bite  well  below  the  limiting  angle  of  30°.  In  the  first  roughers 
the  difficulties  of  design  are  approximately  the  same  as  those  of  the  three- 
high  bloomer,  and  no  further  explanation  of  these  passes  is  required. 

Preparation  for  the  Rolling:  After  the  passes  have  all  been  con- 
structed properly  in  the  drawing,  a  set  of  working  templets,  including  both 
male  and  female  for  the  cold  templet,  is  made  from  the  drawings.  The 
working  templets  may  be  of  steel.  These  templets  may  number  from  the 
slabber  down  only,  as  the  roil  designer  strives  to  keep  the  roughing  passes 
of  such  shapes  and  sizes  that  the  same  set  may  be  used  for  a  large  number 
of  different  sections  of  the  same  general  design.  When  completed  they  go 
to  the  tool  shop,  where  they  are  used  as  patterns  in  making  a  set  of  tools  t 
for  turning  the  rolls  for  the  section.  For  the  last  six  passes,  that  is,  number- 
ing from  the  slabber  to  the  finishing,  inclusive,  twenty-two  different  tools 
are  required  for  each  type  and  size  of  rail.  After  shaping  these  tools  to  a 
little  over  size,  they  are  tempered  and  then  redressed  to  exact  size  before 
they  can  be  used  to  turn  the  rolls.  When  ready,  templets  and  tools  pass  to 
the  roll  shop,  where  the  work  of  turning  the  rolls  is  done.  Here  the  templets 


444 


THE  ROLLING  OF  SECTIONS 


Fia.  78.     Arrangement  of  Rolls  and  Passes  for 


RAIL  MILLS 


445 


Rolling  Heavy  Rails  by  the  Slab-and-Edging  Method. 


446 


THE  ROLLING  OF  SECTIONS 


ire  used  by  the  roll  turner  in  cutting  the  grooves,  which  must  be  of  the 
exact  size  and  shape  of  the  templets.  At  Edgar  Thomson  the  roughing 
rolls  are  adamite  or  sand  rolls,  more  often  the  latter;  the  second  rougher, 
or  former,  are  sand  rolls;  and  the  finishing  are  chilled  rolls. 


1st  Houghing  Stand. 


1st  Finishing  Stand. 


2nd  Roughing  Stand.  2nd  Finishing  Stand. 

Fia.  79.    Plan  Showing  Arrangement  of  Rolls  for  Diagonal  Rolling  of  Rails  from  Billets 


RAIL  MILLS  447 


The  Diagonal  Method  of  rolling  is  represented  on  the  accompanying 
cut  of  a  light  rail  mill  where  this  method  is  employed  altogether.  It 
differs  from  the  slabbing  method  in  that  the  shaping  of  the  rail  is  begun 
with  the  first  pass  in  the  roughers  and,  instead  of  first  compressing  the 
bloom  to  a  smaller  size  and  then  forming  the  section  partly  through  com- 
pression and  partly  by  spreading,  the  process  is  one  of  compression  from 
beginning  to  end,  as  must  be  evident  from  observing  the  position  of  the 
piece  in  passing  through  the  rolls.  From  a  quality  standpoint  the  method 
is  thought  to  possess  some  advantage  over  the  slabbing  method  by  virtue 
of  the  fact  that  a  greater  amount  of  work  is  done  on  the  tops  of  the  head 
and  flange,  where  it  is  needed.  From  the  operator's  standpoint  it  would 
seem  to  have  both  advantages  and  disadvantages.  As  an  instance  of  the 
former,  it  is  pointed  out  that  the  angular  grooves  make  it  easier  to  redress 
the  rolls  and  tend  to  give  them  a  greater  life,  because  the  cuts  to  restore 
the  section  need  not  be  so  deep.  To  restore  a  section  of  the  flat  grooving, 
cuts  as  deep  as  one-half  inch  are  usually  required  on  smaller  sections,  while 
as  much  as  three-fourths  inch  is  needed  on  the  larger  ones.  The  chief 
disadvantage  of  using  the  method  lies  in  the  great  side  thrust  of  the  rolls, 
which  is  very  undesirable  and  difficult  to  provide  for.  It  also  requires  more 
roll  space  than  the  flat  method  for  the  same  number  of  passes. 

The  Mills:  There  are  four  rail  mills  at  the  Edgar  Thomson  plant, 
but  one  of  these,  the  oldest,  is  used  exclusively  for  rolling  sheet  bar,  billets, 
etc.  Of  the  mills  used  for  rolling  rails,  No.  1  mill  is  the  older.  It  consists 
of  three  stands  in  tandem,  each  separately  driven.  The  first  roughing 
stand  is  driven  by  a  40"  x  78"  x  60"  horizontal  vertical  compound  con- 
densing engine,  and  the  rolls  are  twenty-eight  inches  in  diameter.  The 
second  stand,  driven  by  a  50"  x  78"  x  60"  tandem  compound  condensing 
engine,  contains  rolls  twenty-seven  and  one-half  inches  in  diameter.  The 
finishing  stand,  which  is  two-high,  is  made  up  of  rolls  twenty-five  and  one- 
half  inches  in  diameter,  and  is  driven  by  a  32"  x  56"  x  48"  tandem  compound 
condensing  engine.  This  mill,  originally  built  for  a  twenty-four  inch  mill, 
is  evidence  of  the  rapid  increase  in  the  size  of  roll  sections  and  the  extremities 
the  mills  are  put  to  in  order  to  meet  the  demands  made  upon  them  for 
heavier  rails.  The  mill  now  rolls  rails  from  twenty-five  pounds  to  one 
hundred  pounds  per  yard.  The  No.  2  mill  was  completed  in  the  early  part 
of  1916  and  is  designed  to  roll  rails  up  to  one  hundred  fifty  pounds  per  yard, 
which  weight,  it  is  hoped,  will  meet  all  demands  for  some  years  to  come. 
Up  to  1918  the  largest  section  rolled  was  a  hundred  thirty  pound  rail.  In 
this  mill  all  the  rolls  are  thirty-two  inches  in  diameter,  when  new.  The 
pitch  of  the  pinions  is  twenty-nine  inches,  which  adapts  the  mill  to  rolls 
as  small  as  twenty-eight  inches  in  diameter.  Like  the  No.  1  mill,  the 
No.  2  is  made  up  of  three  trains  in  tandem,  but  the  first  roughing  train 
contains  two  stands  in  order  to  provide  ample  roll  space  for  rolling  large 
sections  by  either  the  flat  or  diagonal  methods.  The  bodies  of  the  rolls 
in  the  first  three  stands  are  sixtv-four  inches  in  length,  while  in  the 


448  THE  ROLLING  OF  SECTIONS 

finishing  this  dimension  is  reduced  to  forty  inches.  The  first  and  second 
trains  are  driven  by  50"  x  78"  x  60"  tandem  compound  engines.  The  fly 
wheels  on  these  engines  weigh  100  tons  each,  and  the  speed  of  the  engine 
is  about  60  r.  p.  m.  The  third  train  is  driven  by  a  44"  x  74"  x  54" 
horizontal  vertical  compound  engine,  which  has  a  speed  of  65  r.  p.  m. 
The  first  or  roughing  stands  on  each  of  these  two  mills  are  served  by  lifting 
tables,  and  the  intermediate  stands  by  tilting  tables.  The  No.  3,  an  eighteen 
inch  mill,  employs  19"  x  42",  19"  x  38"  and  19"  x  20"  rolls,  and  rolls  rails 
from  twelve  pounds  to  forty  pounds  per  yard.  It  consists  of  two  trains 
in  tandem,  each  of  two  stands;  number  one  and  number  three  stands,  both 
three-high,  make  up  the  first  train,  while  number  two,  a  three-high  stand, 
and  the  two-high  finishing  stand  are  in  the  second  train.  Each  train  is 
independently  driven  by  a  1500  h.  p.  electric  motor.  Rails  rolled  on  these 
mills  have  distinguishing  marks.  Thus,  heavy  rails  rolled  on  the  No.  2 
mill  have  the  sign,  9  ,  rolled  on  the  web,  and  light  rails  rolled  on  the  No.  I 
mill  are  distinguished  by  the  sign,  — ,  similarly  located. 

Rolling  Heavy  Rails:  After  the  rolls  have  been  properly  turned 
they  are  placed  in  the  housing  in  their  proper  positions  and  carefully  lined 
up.  A  trial  rolling  on  a  short  bloom  will  then  be  made,  and  during  this 
rolling  the  boss  roller  will  watch  the  piece  closely  to  see  that  it  goes  through 
the  mill  all  right.  If  the  section  is  a  new  one,  the  roll  turner  and  designer 
will  also  be  present  to  watch  the  trials.  If  the  trial  piece  goes  through 
the  mill  without  causing  trouble,  a  section  is  sawed,  cooled,  and  examined 
by  the  roller  and  roll  designer.  In  doing  this,  the  piece  thus  rolled  is  gauged 
by  means  of  the  male  and  female  templet  which  the  designer  has  furnished 
the  roller.  If  this  section  is  found  to  be  correct,  the  mill  is  then  ready  to 
begin  the  rolling,  which  is  really  the  simplest  part  of  the  process.  The  roller 
watches  the  mill  closely  to  see  that  everything  is  running  right,  and  at 
frequent  intervals  will  gauge  and  examine  samples  of  the  rails.  In  addition, 
he  walks  down  to  the  cooling  bed  about  every  fifteen  minutes  to  examine 
the  rails  for  any  defects  that  may  be  caused  in  the  rolling,  such  as  collar 
marks,  underfills,  roll  marks,  overfills,  guide  marks,  cracks  or  seams.  If 
he  finds  a  defect  in  rolling,  he  hastens  to  make  the  necessary  adjustments 
to  correct  the  trouble. 

Unavoidable  Variations:  One  of  the  things  that  cannot  be  avoided 
in  the  rolling  is  the  wear  of  the  rolls.  While  it  occurs  over  the  entire  surface 
of  the  groove  the  parts  of  the  groove  subject  to  fastest  wear  are  those 
which  do  the  greatest  work.  Referring  to  the  photograph  of  the  drawing 
for  the  pass  templets,  it  may  be  seen  where  the  greatest  wear  will  take 
place.  This  results  in  a  decrease  in  the  fishing  of  the  rail  as  shown  in  the 
following  sketch.  It  is  also  a  difficult  matter  to  keep  the  base  perfectly 
flat,  because  the  high  collar  in  the  finishing  passes  supporting  this  part  of 
the  rail  tends  to  wear  away  the  edges  faster  than  at  the  bottom  of  the  groove. 


STEPS  IN  SHAPING  RAILS 


449 


The  slight  overfill  that  results  produces  the  defect  known  as  the  rocking 
H™      This  wearing  is  very  rapid,  and  with  the  mill  running  steadily,  one 


base. 


dressing  of  the  rolls  lasts  but  from  twenty-four  to  thirty-six  hours. 


Overfills 


Underfill 


Decrease  in  the 
Fishing  due  to 
Worn  Roll 


Hocking  Base 
FIG.  80.     Showing  Defects  in  Rails  Due  to  Wearing  of  the  Rolls. 


The  Various  Steps  in  Shaping  of  Rails:  To  trace  the  material  from 
the  ingot,  the  work  begins  at  the  forty-eight  inch  mill  previously  mentioned, 
where  the  very  slow  speed  and  relatively  great  reduction  gives  more  of 
the  pressing  and  less  of  the  stretching  effect  of  rolling,  and  is  intended  to  avoid 
much  of  the  danger  of  tearing  or  cracking  the  ingot.  The  large  fillets  used  in 
the  grooves  keep  the  corners  of  the  ingot  well  rounded.  This  mill,  reducing 
the  ingot  from  233^"  x  23^"  to  15^"  x  18^"  leaves  less  work  than  usual 
to  be  done  on  the  three-high  bloomer  which  produces  a  9}^"  x  9^"  bloom. 
From  the  bloomer  the  long  bloom  passes  to  the  shears  where  the  proper 
discard,  which  is  varied  in  different  specifications,  is  made,  and  blooms  of 
different  lengths  are  cut  to  suit  the  conditions.  Large  rails  are  rolled  two 


450  THE  ROLLING  OF  SECTIONS 


lengths  to  the  bloom,  while  lighter  ones  may  run  into  three  lengths  to  the 
bloom.  Leaving  the  shears,  the  blooms  travel  on  roll  tables  to  a  distri- 
buting point,  where  they  are  sent  to  No.  1  and  No.  2  rail  mill  furnaces  or 
to  No.  4  billet  and  sheet  bar  mill.  The  furnaces  serving  the  two  large 
rail  mills,  which  extend  parallel  to  each  other  and  are  housed  in  the  same 
building,  are  arranged  in  one  row  at  right  angles  to  the  mills  and  in  such 
a  manner  that  the  blooms  may  be  charged  on  one  side  and  drawn  on  the 
other  which  is  nearer  the  mills.  From  the  rolls  the  piece  passes  on  to  the 
saws,  and  then  to  the  finishing  and  inspecting  department. 

Cutting:  For  cutting  rails  four  high  speed  (1500  r.  p.  m.)  toothed 
circular  saws  are  provided.  The  saws  are  mounted  over  the  delivery  table 
on  the  free  ends  of  tilting  arms,  whose  axes  are  concentric  with  the  drive 
shafts.  Belts  then  connect  the  saws  with  their  driving  shafts,  which  are 
electrically  propelled.  On  No.  1  mill  all  the  saws  are  mounted  on  one  shaft 
which  is  driven  by  one  motor,  but  in  No.  2  mill  each  saw  is  mounted  on  a 
separate  carriage  and  is  driven  by  an  individual  motor.  The  tilting  arms 
are  electrically  controlled  so  that  all  the  saws  may  be  made  to  cut  simul- 
taneously. These  saws  are  adjustable  to  cut  different  lengths  from  thirty 
to  sixty  feet,  though  thirty  and  thirty-three  feet  are  standard  lengths.  In 
cutting  the  rails,  proper  allowance  must  be  made  for  shrinkage,  which  is 
nearly  three-sixteenths  inch  per  foot,  or  about  seven  inches  for  a  thirty- 
three  foot,  hundred  pound  rail.  The  exact  amount  of  the  shrinkage  depends 
upon  the  temperature  at  which  the  rail  is  sawed,  hence  many  railroads 
specify  the  amount  of  shrinkage  per  rail,  and  in  so  doing  fix  the  finishing 
temperature  of  rolling.  The  allowance  should  be  not  less  than  one-fourth 
inch  over  or  under  length  specified.  Since  the  rails  do  not  always  leave 
the  finishing  rolls  perfectly  straight,  it  is  not  always  possible  to  make  a 
square  cut,  and  one-thirty-second  inch  off-square  should  be  allowed.  Rails 
eighty-five  pounds  or  over  are  rolled  in  double  lengths,  and  on  blooms  on 
which  tests  are  taken,  six  to  eight  feet  is  allowed  for  physical  test  pieces, 
which  are  cut  from  the  ends  of  the  piece.  Smaller  rails  are  rolled  in  triple 
lengths.  Great  care  is  required  in  adjusting  the  height  of  the  saw  blocks 
in  order  to  avoid  kinking  or  scratching  the  rail,  and  to  secure  a  square  cut. 
From  the  saws,  the  rails  pass  under  a  stamping  machine,  which  marks  the 
heat  number  and  the  position  of  the  rail  in  the  ingot,  the  latter  being  desig- 
nated by  letters  beginning  with  A  at  the  top  of  the  ingot.  At  Edgar  Thom- 
son the  A  cut  is  discarded  on  all  heavy  rails.  About  sixty  feet  from  the 
stamper,  is  located  the  cambering  machine  which  consists  of  a  set  of 
horizontal  rolls  with  a  vertical  roll  on  each  side,  all  in  one  housing,  and  set 
to  bend  the  rail  slightly  so  as  to  make  the  top  surface  of  the  rail  convex 
from  end  to  end.  A  scale  located  near  the  end  of  the  delivery  table  is  used 
for  checking  the  weight  of  the  rails  as  often  as  desired,  before  they  are  sent 
to  the  cooling  beds.  The  No.  1  and  No.  2  mills,  being  arranged  parallel 
to  each  other,  deliver  their  product, to  what  may  be  considered  a  single 
large  cooling  bed,  where  the  rails  from  both  mills  are  slowly  moved  in  one 
direction,  which  is  toward  the  finishing  room. 


FINISHING  RAILS  451 


Recording:  A  complete  record  is  kept  of  all  the  steel  rolled  in  the 
mills  from  the  time  it  is  made  in  the  open  hearth  or  Bessemer  converter 
until  it  is  shipped.  This  work  is  done  by  the  recorder,  who  traces  the 
material  through  the  mills,  and  is  so  complete  that  it  is  easy  to  show,  not 
only  the  kind  of  steel  from  which  each  rail  is  rolled,  but  the  heat,  the  number 
of  ingot,  and  its  position  in  the  ingot.  At  these  mills  the  work  of  tracing 
the  material  is  much  facilitated  by  the  use  of  an  electric  signalling  system. 

Finishing  and  Inspection:  The  finishing  room  is  arranged  to  the 
best  advantage  possible  for  handling  the  rails.  In  it  are  located  the 
straightening  and  drilling  machines  (fourteen  in  number)  in  two  rows  parallel 
to  each  other  and  to  the  two  mills,  and  extending  in  the  same  direction 
beginning  at  the  mill  side  of  the  cooling  beds.  Between  the  row  of 
straighteners  and  the  cooling  beds  is  a  system  of  roll  tables,  which  carry 
the  rails  from  the  beds  and  distribute  them  to  the  different  straighteners. 
Here  the  rails  are  marked  with  a  stamp  to  indicate  the  individual  work- 
men responsible  for  this  part  of.  the  work.  The  straightening  machines, 
or  gag  presses,  are  provided  with  a  bottom  bed,  on  which  the  rail  is 
supported  at  two  points  from  below,  and  a  top  block  which  moves  up  and 
down  between  these  two  supporting  lines  with  a  fixed  stroke  of  such  length 
that  the  block  will  not  touch  the  rail  by  about  two  inches  at  its  lowest  point. 
The  block  has  a  double  face,  each  side  of  which  is  inclined  toward  the 
center  line,  where  the  faces  cut  each  other.  This  form,  combined  with  the 
different  dimensions  of  the  gag,  a  rectangular  shaped  block  of  steel  which 
is  inserted  between  the  face  of  the  block  and  the  rail  to  be  straightened, 
makes  it  possible  to  control  the  amount  of  bend  that  the  rail  receives  and 
to  adapt  the  machine  to  the  different  dimensions  of  a  rail.  For  the  different 
sizes  of  rails,  the  faces  of  the  blocks  are  made  adjustable  by  means  of  set- 
screws  and  liners,  while  for  different  sections  different  gags  must  be  used. 
To  straighten  a  rail,  one  workman  is  stationed  in  front  of  the  machine  and 
another  at  the  end.  By  sighting  along  the  rail,  the  man  at  the  end  locates 
the  crooks  in  the  rail  and  brings  them  under  the  blocks,  while  the  man 
before  the  machine,  acting  under  directions  from  the  workman  at  the  end, 
inserts  the  gag  in  such  a  way  that  the  stroke  of  the  machine  will  bend  the 
rail  enough  to  straighten  it,  which  requires  that  the  rail  be  bent  beyond 
its  elastic  limit  in  order  to  give  a  permanent  set.  Next,  the  burrs  made 
by  the  saws  on  the  ends  of  the  rails  are  cut  off  with  chisels,  and  smoothed 
with  a  file.  The  rails  are  then  given  a  preliminary  inspection  by  an  employee 
of  the  Company,  in  order  to  avoid  unnecessary  work  being  done  on  rails  that 
may  be  rejected.  As  the  inspection  is  completed,  the  rails  are  moved  to  the 
drilling  machines,  which  are  arranged  in  pairs  and  so  spaced  that,  when  one 
machine  has  completed  the  drilling  on  one  end  of  the  rail,  it  is  moved  under 
the  other  machine  which  drills  the  holes  in  the  opposite  end.  These  machines 
are  each  provided  with  three  drilling  spindles,  the  middle  of  which  is  fixed, 
and  may  be  made  to  drill  from  one  to  three  holes  at  one  time.  The  rails 
are  then  moved  sidewise  through  openings  in  the  building  to  the  inspection 


452  THE  ROLLING  OF  SECTIONS 

beds  where  they  are  walked,  or  inspected,  both  by  a  company's  inspector 
and  by  the  customer's,  if  so  specified.  The  outside  inspection  covers  mainly 
surface  defects,  such  as  seams,  slivers,  guide  marks,  and  pits  that  may 
have  been  overlooked  by  the  inside  inspector,  and  the  bolt  holes.  The 
rails,  having  been  measured  and  gauged  by  the  inside  inspectors  and  rollers, 
the  dimensions  are  checked  only  at  intervals  by  the  outside  inspector. 
The  location  of  the  defects  are  marked  with  chalk.  If  these  are  located 
near  the  end,  that  portion  of  the  rail  may  be  sawed  off  and  the  rail  still 
applied  on  the  order  as  a  short  of  first  grade.  Rails  that  fall  below  the 
allowance  as  to  length  are  also  disposed  of  in  the  same  way.  If  the  defects 
are  many  or  near  the  center,  the  rail  is  either  classed  as  a  number  two  or 
sent  back  to  the  mills  to  be  rolled  into  a  light  rail.  In  both  the  inside  and 
outside  inspection,  the  rails  are  walked  twice,  once  with  the  base  up,  again 
with  the  heads  up.  As  the  rails  are  accepted  by  the  inspectors,  -they  are 
counted,  the  number  being  checked  up  with  the  original  order.  Then 
they  are  picked  up  by  immense  magnets  attached  to  over  head  electric  cranes 
and  placed  in  the  cars  where,  after  weighing,  they  are  ready  for  shipment. 

Light  Rails :  The  rolling,  finishing  and  inspection  of  light  rails,  as 
well  as  the  material  used,  are  somewhat  different  from  the  same  operations 
for  heavy  rails.  To  begin  with,  the  number  three  mill  in  which  most  of 
these  rails  are  rolled,  is  operated  as  a  separate  unit,  practically  independent 
of  the  rest  of  the  works,  and  with  the  exception  of  re-rollings  from  rejected 
heavy  rails,  all  its  product  is  rolled  from  billets  which  are  obtained  from 
other  works.  For  this  reason  neither  check  analyses  nor  physical  tests  are 
made  on  light  rails,  because,  even  if  such  tests  were  made,  there  would  be 
no  way  of  indentifying  the  rail  as  having  been  made  from  the  same  steel  from 
which  the  tests  were  taken  nor  of  knowing  that  the  tests  represented  the 
material  in  an  order.  The  billets  are  heated  in  one  of  two  continuous  gas 
fired  furnaces  and  are  rolled  by  the  angular  method  on  six  passes  in  the  mill. 
Rerolled  rails  receive  two  additional  passes  in  the  first  roughing  stand, 
which  is  provided  with  tilting  tables  for  the  purpose.  Leaving  the  rolls, 
the  rails  are  sawed  into  lengths  of  thirty  feet  or  under  and  are  passed  to  the 
cooling  beds.  When  sufficiently  cold  they  receive  a  preliminary  inspection, 
in  which  they  are  measured  for  length,  and  then  passed  through  a  roll 
straightener  to  punching  machines  where  both  bolt  holes  and  bond  holes 
are  punched.  Since  the  roll  straighteners  straighten  the  rail  in  one  direction 
only  and  usually  fail  to  produce  a  perfectly  straight  rail,  even  in  one 
direction,  gag  presses  are  employed  to  complete  the  straightening.  As  for 
heavy  rails,  light  rails  are  subject  to  a  second,  though  less  rigid,  inspection 
after  all  work  is  completed.  The  mill  is  also  equipped  with  cold  saws, 
but  cold  sawing  is  undesirable,  for  it  works  a  great  hardship  upon  the  mill, 
increasing  the  cost  greatly,  due  to  extra  labor  and  scrap  loss.  For  handling 
the  rails  a  large  gantry  crane  of  an  improved  form  which  travels  on  tracks 
laid  on  the  ground  is  provided.  Light  rails  are  weighed  in  cars  before 
shipment. 


RAIL  JOINTS 


453 


Continuous  Rail  Joint. 


Weber  Rail  Joint. 


Duquesne  Rail  Joint. 


100  Per  Cent  Rail  Joint. 


Duquesne  and  100  Per  Cent  Joint. 


Hatfield  Rail  Joint. 


Wolhaupter  Rail  Joint. 


Barschall  Rail  Joint. 


Q  &  C  Bonzano  Rail  Joint. 


Abbott  Rail  Joint. 


Williams  Reinforced  Rail  Joint.  Atlas  Rail  Joint 

Fia.  81.     Sketches  Showing  Different  Kinds  and  Types  of  Rail  Joints. 


454 


THE  ROLLING  OF  SECTIONS 


Continuous  Insulated  Rail  Joints 


Keystone  Insulated  Rail  Joint 


Weber  Insulated  Rail  Joint 


Braddock  Insulated  Rail  Joint 


O'Brien  Insulated  Rail  Joint 


FIG.  82.     Types  of  Insulating  Rail  Joints. 
The  heavy  black  lines  represent  insulating  fiber. 


SECTION  II. 

THE   SHAPING  OF  RAIL  JOINTS. 

•  Rolling  Rail  Joints:  Rail  joints  are  made  in  so  many  different  forms, 
it  is  impossible  to  select  any  one  that  would  serve  as  an  example  to  illustrate 
the  problems  involved  in  the  rolling  of  the  others.  The  accompanying 
prints  show  the  shapes  of  the  different  passes  for  each  of  three  types  of 
rail  joints,  namely,  the  common  splice  bar,  the  Duquesne  joint  of  the 
depending  flange  type,  and  the  continuous  joint  of  the  bed  plate  type.  The 
Braddock  insulated  joint  is  made  up  of  two  side  plates  and  a  bed  plate, 
both  being  comparatively  simple  to  roll.  In  a  general  way,  rail  joints  are 
more  or  less  difficult  to  roll,  being  subject  to  all  the  drawbacks  of  the  rail 
section  and  to  many  others  in  addition,  due  to  their  irregular  section  and 
lack  of  symmetry.  In  the  common  splice  bar,  for  example,  the  angles  at 
which  the  section  is  rolled  are  limited  by  danger  of  undercuts,  and  the 
shape  of  the  passes  in  which  the  piece  is  necessarily  reduced  are  favorable 
to  the  formation  of  laps  and  seams.  In  the  Duquesne  joint,  these  dangers 


RAIL  JOINTS 


455 


FIG.  83.     Passes  for  Rolling  Common  Splice  Bar. 


456 


.  THE  ROLLING  OF  SECTIONS 


FIG.  84.     Passes  for  Rolling  Duquesne  Splice  Bar. 


RAIL  JOINTS 


458  THE  ROLLING  OF  SECTIONS 

are  multiplied,  while  the  outstanding  parts  of  the  continuous  section,  by 
striking  the  rolls  first  or  being  a  trifle  colder  than  the  rest,  often  prevent 
the  piece  from  entering  the  pass  rightly.  For  similar  reasons,  it  is  difficult 
to  make  guides  that  will  properly  handle  this  material,  and  it  is  prone  to 
become  cobbled  or  caught  in  the  rolls  of  the  tables.  The  base  plate 
part  of  the  continuous  joint  must  be  rolled  at  the  angle  as  shown  on  the 
drawings.  This  part  is  later  bent  up  hot  at  the  splice  bar  shop  to  fit  neatly 
the  flange  of  the  rail.  After  being  rolled,  usually  in  pieces  about  ninety- 
three  feet  long,  the  bars  are  hot  sawed  into  three  equal  lengths,  and  sent 
to  the  splice  bar  shop,  which  is  located  at  the  Edgar  Thomson  Works. 
Here  they  are  sheared  to  lengths  required,  punched,  slotted  and  straightened 
by  methods  shortly  to  be  described. 

Methods  of  Finishing  Rail  Joints:  While  the  finishing  of  rail  joints 
bears  no  relation  to  the  rolling  of  them  and  is  a  separate  industry,  yet  for 
the  convenience  of  the  reader  it  is  best  to  complete  the  subject  now,  rather 
than  to  postpone  it  for  some  other  part  of  the  book.  There  are  four  ways 
by  which  rail  joints  may  be  worked:  First,  all  the  operations  of  shearing 
to  length,  straightening,  punching  and  notching  may  be  performed  upon 
the  cold  pieces  without  heating  in  any  way,  when  they  are  spoken  of  as 
cold  worked  joints.  Second,  this  cold  working  may  be  followed  by  an 
annealing  process  to  produce  the  cold  worked  and  annealed  bars.  Third, 
the  bars  may  be  heated,  after  shearing  to  length,  and  the  work  of  punching, 
etc.,  be  done  while  they  are  hot,  after  which  they  are  allowed  to  cool  in 
air.  In  this  case  they  are  called  hot  worked  bars.  Fourth,  instead  of 
cooling  the  bars  in  the  air  after  hot  working  they  may  be  cooled  by  immers- 
ing them  in  oil,  when  they  are  designated  as  hot  worked  and  oil  quenched 
bars.  It  will  be  observed  that  all  bars,  no  matter  by  what  method  they 
are  to  be  worked,  are  sheared  cold,  hot  or  cold  sawing  being  too  expensive 
to  be  considered.  Of  course,  these  methods  of  treatment  may  be  varied 
somewhat,  but  it  is  doubtful  if  the  additional  benefits  derived  are  com- 
mensurate with  the  additional  expense  involved. 

The  Edgar  Thomson  Splice  Bar  Shop:  The  practice  at  this  shop 
coincides  with  that  outlined  above.  For  this  reason  the  shop  is  made 
up  of  four  units  designated  as  A,  B,  C,  and  D,  of  which  all  may  be  used  for  cold 
working,  but  only  A,  B,  and  C  are  equipped  with  furnaces  for  hot  working. 
The  furnace  of  unit  B  is  used  for  heating  continuous  joints  prior  to  bending  the 
depending  flange.  Units  A  and  D  each  consist  of  a  shear  and  two  presses 
for  punching.  A  gag  press  for  straightening  such  bars  as  need  it  is  also 
provided.  Unit  B,  which  is  especially  equipped  for  working  continuous 
joints,  consists,  in  addition  to'  the  furnace  noted  above,  of  one  shear,  two 
punches,  and  a  folding  press,  which  not  only  folds  the  joint  but  also 
straightens  down  the  flange  forming  the  bed  plate,  all  in  the  one  operation. 
The  Duquesne  bar  likewise  requires  a  special  tool  for  cutting  out  the  excess 
in  the  depending  flange.  For  this  reason,  unit  C  consists  of  two  punches, 
a  straightening  press,  and  two  shears.  A  continuous  oil  quenching  tank 


FINISHING  RAIL  JOINTS  459 

and  two  large  annealing  furnaces  complete  the  main  equipment  of  the  shop 
proper,  while,  in  addition,  a  section  of  the  shop  is  given  to  assembling 
insulated  joints.  A  machine  shop  for  making  the  dies  for  punching  and 
shearing  is  housed  in  a  building  adjoining  the  working  shop. 

Cold  Worked  Bars :  In  this  method  the  order  of  working  is  this :  First , 
the  bars  are  sheared  to  length,  inspected  for  straightness  and  flaws, 
straightened,  if  necessary,  punched  and  slotted.  The  dies  on  the  shears 
are,  in  all  cases,  made  to  conform  exactly  to  the  shape  of  the  bars,  so  that 
a  nice  clean  cut  is  made  without  in  any  way  deforming  the  bar.  However, 
in  shearing  the  continuous  joint,  a  slight  bending  of  the  outer  edge  at  one 
end  is  unavoidable.  For  a"  similar  reason,  the  bottom  blocks,  or  dies,  of  the 
punching  and  notching  machine  support  the  web  while  the  punches  descend 
from '  above,  pushing  the  material  through  conforming  openings  in  the 
blocks.  All  dies  are  made  of  the  highest  grade  of  special  tool  steels  and 
are  kept  in  the  best  possible  condition.  In  this  way  the  hole  is  made  as 
smooth  as  it  is  possible  to  make  it  by  punching.  It  is  evident  that  it  is  a 
great  advantage  to  the  shop  to  have  the  bolt  holes  on  each  bar  alternately 
round  and  oval  rather  than  all  oval  or  all  round,  for  in  the  latter  case  only 
every  other  bar  could  be  punched  on  one  arrangement  of  the  dies,  and  the 
bars  would  require  careful  matching.  As  to  the  effect  of  cold  working,  it 
is  quite  clear  that  the  bars  of  low  carbon  content,  under  .28%  carbon,  soon 
recover  from  the  effects  of  the  working,  but  in  the  higher  carbon  bars  these 
effects  are  permanent  and  may  do  injury  to  the  bar.  On  the  entering  side 
of  the  punches  the  metal  is  compressed  beyond  its  ultimate  strength,  while 
the  material  on  the  opposite  side  is  put  under  a  tension,  as  may  be  observed 
by  an  examination  of  any  hole  made  by  punching.  One  of  the  direct  results 
of  this  cold  working  is  to  increase  the  hardness  of  the  metal  about  the  hole, 
but  the  worse  effect,  which  applies  only  to  high  carbon  bars,  is  found  in 
the  very  small  cracks  which  extend  into  the  metal  along  lines  perpendicular 
to  the  surface  of  the  hole.  For  these  reasons,  cold  working  is  the  most 
objectionable  of  all  the  methods  cited.  The  difficulties,  as  well  as  the  evil 
effects  of  cold  working,  increase  as  the  carbon  content  of  the  steel  increases. 
Hence,  only  low  carbon  bars  (below  .28%  C.)  should  be  cold  worked.  As 
a  rule  the  method  is  applied  to  the  smaller  angle  bars  and  fish  plates. 

Cold  Worked  and  Annealed  Bars:  The  fine  cracks  due  to  cold  working 
cannot  be  eradicated  by  subsequent  treatment,  but  the  internal  stresses 
and  strains  are  relieved  by  annealing  and  the  bar  as  a  whole  is  made  more 
ductile.  Hence,  some  specifications,  more  particularly  on  angle  bars  and 
insulated  joints,  will  call  for  cold  working  to  be  followed  by  annealing. 
The  annealing  furnaces  provided  at  this  shop  are  divided  into  two  sections, 
a  heating  chamber,  which  is  fired  with  natural  gas,  and  a  cooling  chamber. 
The  bars  to  be  annealed  are  piled,  crib  fashion,  upon  steel  supports  that 
rest  on  brick  bottomed  cars,  which  are  pushed  into  the  furnace.  The 
furnace  is  then  heated  to  a  temperature  slightly  above  the  critical  point  of 


460  'THE  ROLLING  OF  SECTIONS 

the  steel.  The  proper  temperature  once  reached,  it  is  maintained  until  all 
the  steel  is  thoroughly  heated,  which  generally  takes  about  two  and  one- 
half  hours.  The  heat  is  then  turned  off  and  all  doors  in  the  furnace  are 
closed.  The  steel  is  now  pushed  into  the  cooling  chamber,  where  it  is 
allowed  to  cool  slowly.  During  this  time  the  doors  are  closed  tightly  to 
prevent,  as  much  as  possible,  scale  forming  on  the  steel.  The  cooling 
requires  about  two  and  one-half  hours.  After  the  steel  is  cold,  the  cars 
are  pushed  out  of  the  furnace,  and  the  bars  are  loaded  on  cars  for  shipment. 

Hot  Worked  Bars:  In  hot  working  common  angle  bars,  the  order  of 
procedure  is  as  follows:  shearing  to  length,  heating,  punching,  notching, 
straightening,  if  necessary,  and  cooling.  Patented  bars  may  require 
additional  operations.  Thus,  in  working  the  Duquesne  bar,  the  excess 
flange  is  sheared  off  after  the  heating  and  just  before  the  notching.  In 
hot  punching  any  bar,  in  order  to  avoid  spreading  of  the  metal  and  con- 
sequent distortion  of  the  bar,  it  is  necessary  to  employ  a  confining  die, 
that  is,  the  cutting  die  must  be  enclosed  in  a  die  block  or  frame,  the  upper 
surface  of  which,  together  with  the  die  itself,  conforms  in  shape  to  the 
inside  surface  of  the  bar.  Hot  worked  bars  must,  therefore,  be  punched 
from  the  outside,  or  inward.  Most  cold  worked  bars  may  be  punched  from 
the  inside,  or  outward,  as  there  is  no  danger  of  spreading  the  metal  and 
enclosed  dies  are  not  necessary.  The  straightening  machines  are  presses 
provided  with  a  set  of  dies  for  each  size  of  each  section.  One  die  conforms 
to  the  size  and  shape  of  one  side  of  the  section  and  the  second  die  to  the  other 
side,  and  both  are  set  in  the  press  so  that  at  the  end  of  the  stroke  the  space 
between  the  dies  is  of  the  same  shape  as  the  bar  and  just  equal  to  it  in 
thickness.  As  a  rule  the  higher  carbon  angle  bars,  Duquesne  and  con- 
tinuous joints  are  hot  worked.  In  case  the  continuous  joints  are  cold 
worked,  they  must  be  heated  before  the  flange  is  bent  down.  The  furnaces 
employed  for  hot  working  are  of  the  continuous  type.  They  are  rectangular 
in  shape  and  wide  enough  to  admit  two  rows  of  bars  laid  end  to  end.  Natural , 
gas  is  the  fuel  used.  In  order  to  obtain  an  even  distribution  of  the  heat, 
the  furnace  is  provided  with  four  ports,  and  in  addition  four  large  burners 
of  the  Bunsen  type  are  located  at  the  bottom  along  each  side  of  the  furnace 
to  supply  heat  under  the  bars.  Recording  pyrometers  are  employed,  so  the 
exact  temperature  of  the  furnace  may  be  ascertained  at  any  time.  After 
being  sheared  to  length,  the  cold  bars  are  laid  upon  water  cooled  skid  pipes 
and  pushed  into  the  furnace  from  the  rear  by  means  of  electricall}7  operated 
dogs.  The  length  of  the  furnace  and  rate  of  charging  is  such  that  about 
two  hours  are  consumed  in  pushing  each  bar  through  the  furnace,  this 
time  being  sufficient  to  bring  the  bar  to  the  working  temperature  of  about 
800°  to  830°  C.,  which  is  a  little  higher  than  necessary  for  working,  as  the 
temperature  drops  by  the  time  the  bar  reaches  the  machine  to  790°  or  815°. 
The  skids  end  near  the  front  of  the  furnace,  and  the  bars  descend  to  a  hearth, 
whence  they  are  removed  with  tongs  through  doors.  Needless  to  say,  the 
bad  effects  of  cold  working  are  entirely  avoided  by  hot  working. 


STRUCTURAL  SHAPES  461 

Hot  Worked  and  Oil  Quenched:  In  this  method,  not  only  are  the 
evils  of  cold  working  avoided,  but  the  strength  and  ductility,  or  toughness, 
of  the  bar  are  much  improved,  also.  The  method,  which  is  especially 
applicable  to  high  carbon  angle  bars  and  Duquesne  joints,  consists  in  hot 
working  the  bars  in  the  usual  way  and  quenching  them  in  oil  before  they 
have  cooled  to  a  temperature  below  that  of  the  critical  range.  The  neces- 
sity of  completing  the  work  before  the  temperature  drops  below  this  point 
may  require  the  bar  to  be  heated  to  30°  or  40°  C.  higher  than  for  ordinary 
hot  working,  and  permits  no  delay  in  the  operation.  For  quenching  the 
bars,  a  continuous  oil  tank  in  close  proximity  to  the  presses  is  provided. 
The  tank  is  rectangular  in  shape  and  provided  with  a  chain  conveyor,  which 
slowly  carries  the  bars  through  the  oil,  the  speed  of  the  chain  and  its 
direction  of  travel  being  so  regulated  that  the  bars,  upon  entering  at  one 
end  of  the  tank,  are  carried  down  into  the  oil,  across  the  tank,  and  up  to 
the  opposite  end  and  are  cooled  to  70°  C.  or  less.  The  oil  used  is  a  special 
grade  of  petroleum  product  that  will  not  get  viscous  and  has  the  most 
favorable  cooling  properties.  In  order  to  keep  it  cooled  to  the  proper 
temperature,  the  oil  from  the  quenching  tank  is  pumped  through  a  set  of 
water  cooled  pipes  and  into  a  large  storage  tank.  The  fresh  oil  for  the 
quenching  tank  is  pumped  from  the  bottom  of  this  tank.  By  means  of 
this  circulating  system  the  temperature  of  the  oil  is  kept,  usually,  at  about 
60°  C.  The  temperature  of  the  oil  is  taken  at  intervals  of  an  hour  or  so 
to  make  sure  its  temperature  does  not  rise  too  high. 


SECTION   III. 

STRUCTURAL  AND   OTHER   SHAPES. 

• 

Plan  of  Study:  It  is  needless  to  remark  that  a  detailed  description 
of  the  rolling  of  each  of  the  many  sections  included  under  this  heading 
would  result  in  a  very  lengthy  discussion,  and  it  is  doubtful  if  such  a  dis- 
cussion would  prove  to  be  of  much  value  in  accomplishing  the  ends  at  which 
this  book  aims.  Besides,  while  the  rolling  of  each  shape  or  section  presents 
difficulties  peculiar  to  itself  alone,  there  are  certain  problems  common  to 
all  sections,  and  of  these  general  features  an  example  has  already  been 
given  in  the  description  of  the  rolling  of  rails.  Unlike  rail  mills,  structural 
shape  mills  vary  much,  both  in  type  and  equipment,  and  often  the  methods 
for  rolling  a  given  section  must  be  adapted  to  the  mill  conditions.  In 
general,  the  size  of  the  section,  for  economic  reasons,  will  determine  the 
size  of  the  mill,  and  the  different  sizes  of  the  same  section  will  be  rolled 
on  different  mills.  No  one  mill,  therefore,  can  be  selected  as  an  example 
of  the  rolling  of  even  one  of  these  shapes.  For  these  reasons  a  brief  and 
more  or  less  general  discussion  of  the  different  roll  designs  for  some  of  the 
more  common  sections  is  all  that  will  be  attempted  here,  and  it  is  hoped 
the  study  will  be  found  both  interesting  and  profitable. 


462 


THE  ROLLING  OF  SECTIONS 


Angles:  Among  the  first  shapes  to  be  rolled  was  the  angle.  Three 
methods  of  rolling  this  shape  have  been  developed.  In  two  of  these  methods 
the  forming  of  the  angle  is  begun  from  a  rectangular  bloom,  or  if  the  bloom 
is  square,  from  a  rectangular  roughing  pass  in  the  mill.  In  what  may  be 
termed  the  first  method,  the  grooves  are  so  designed  that  each  successive 
pass  from  the  slab  approaches  the  right  angle  of  the  finished  bar,  the  piece 
being  gradually  bent  and  reduced  at  the  same  time.  In  the  second  method, 
called  the  butterfly  method,  the  legs  are  kept  flat  until  the  leader  and 
finishing  passes,  when  they  are  bent  to  form  a  right  angle.  In  the  third 
method,  the  forming  of  the  angle  is  begun  from  a  rectangular  bloom  by 
first  working  off  one  corner  and  then  recessing  it  till  the  desired  thickness 
of  the  legs  is  obtained. 

...Billet. 


FIG.  86.     Methods  of  Rolling  Angles. 

The  Three  Methods  Compared:  The  part  of  the  angle  that  gives 
the  most  trouble  in  rolling  is  the  back  and  the  apex,  which  must  be  square 
and  sharp.  As  shown  in  the  accompanying  sketches,  this  difficulty  is 
overcome  in  the  first  and  second  methods  by  reserving  metal  in  the  first 
passes  on  both  sides  of  the  bar  where  the  apex  is  to  be  formed.  In  the 
last  passes  this  excess  metal  is  available  to  fill  out  what  would  be  lacking 
on  account  of  the  bending,  which  tends  to  draw  the  metal  down  from  the 
apex.  In  the  third  method  the  apex  and  back  are  perfect  from  the  beginning. 
As  to  the  relative  merits  of  the  three  methods,  there  is,  of  course,  much 
difference  of  opinion.  However,  there  are  two  features  about  the  butterfly 
method  that  appears  to  a  decided  advantage  when  compared  with  either 
of  the  other  two.  The  ability  to  employ  an  edging  pass  so  near  the  finishing 


STRUCTURAL  SHAPES 


463 


to  control  the  width  makes  it  possible  to  reduce  the  piece  rapidly  in  the 
roughing  passes  and  so  cut  down  the  total  number  of  passes  required  to 
form  the  section.  Then,  too,  since  nearly  all  the  work  on  the  section  is 
done  in  the  flat  passes,  the  difficulties  encountered  when  deep  grooves  are 
used  in  the  rolls  are  entirely  avoided.  Usually  angles  are  formed  in  from 
nine  to  eleven  passes. 


Butterfly  Method  for  Channels  as  first  designed 


FIG.  87.     Methods  of  Rolling  Channels. 


464  THE  ROLLING  OF  SECTIONS 

The  Channel:  Channels  are  rolled  by  two  distinct  methods  known 
as  the  butterfly  and  beam  roughing  methods.  The  butterfly  method  is 
said  to  have  originated  in  the  year  1873  at  the  Upper  Union  Mills  of  Carnegie, 
Klowman  &  Co.,  and  is  sometimes  called  the  slabbing  method.  In  being 
formed  by  this  method,  the  section  resembles  two  angles  being  rolled  side 
by  side  in  one  set  of  grooves,  and  by  the  same  butterfly  method.  In  the 
second  method  the  bloom,  in  the  rectangular  form,  is  edged  for  the  first 
pass  and  is  then  worked  down  from  each  edge  or  face  alternately  by  grooves 
in  the  roughing  passes  until  it  much  resembles  a  beam,  and  in  reality  it  is 
a  beam  in  the  rough.  Succeeding  passes,  however,  work  off  the  flanges  on 
one  side  of  the  web.  The  function  of  these  temporary  flanges  is  to  supply 
metal  for  holding  the  height  of  the  flanges  on  the  opposite  side,  thus  forming 
a  channel  with  full  sharp  edges  and  square  sides.  This  method  is  said  to 
have  an  advantage  over  the  butterfly  method  in  that  the  roughing  rolls 
may  be  used  either  for  beams  or  channels  and  a  greater  number  of  weights 
may  be  taken  from  the  same  set  of  rolls.  In  rolling  deep  channels  the 
butterfly  method  would  appear  to  overcome  the  difficulty  of  making  the 
flanges  nicely,  but  more  roll  space  is  required  than  in  the  beam  roughing 
method,  and  since  the  great  width  of  the  section  makes  edging  imprac- 
ticable, it  is  more  difficult  to  secure  well  formed  edges  on  large  channels. 
In  the  beam  method,  the  butterfly  idea  is  used  to  some  extent,  and  in  order 
to  obtain  the  proper  height  and  thickness  of  flange  readily,  the  flanges  are 
rolled  at  an  angle  to  the  web  and  finally  bent  to  right  angles  in  the  leader 
and  finishing  pass  in  the  same  way,  though  to  less  degree,  as  in  the  butter- 
fly method.  For  channels,  about  the  same  number  of  passes  are  required 
as  for  angles.  Very  large  channels  are  often  rolled  from  shaped  blooms, 
as  at  the  thirty-five  inch  mill  at  Homestead,  which  works  in  conjunction 
with  the  forty  inch  blooming  mill  to  roll  large  beams  and  channels.  The 
blooms  for  both  these  shapes  have  much  the  same  form,  the  channels  being 
finished  by  the  beam-rougher  method  in  the  thirty-five  inch  mill. 

Beams,  Ties,  and  Piling:  Beams  were,  doubtless,  first  made  by 
riveting  a  plate  and  four  angle  bars  together,  then  later  by  bolting  or 
riveting  two  channels  together  back  to  back.  Up  until  1895  they  were 
considered  very  difficult  sections  to  roll,  but  the  great  demand  for  these 
shapes  during  the  succeeding  years  so  stimulated  thought  in  their  manu- 
facture that  most  of  the  former  difficulties  have  been  overcome,  and  standard 
beams  are  now  rolled  with  as  little  trouble  as  angles,  channels,  or  rails. 
Indeed,  the  rolling  of  these  sections  very  much  resembles  that  of  rails, 
for  if  the  head  of  the  rail  be  replaced  by  a  flange  the  sections  would  be 
practically  the  same.  Like  rails,  there  are  two  methods  of  rolling  beams, 
namely,  the  flat,  or  slab-and-edging,  method  and  the  diagonal.  But  un- 
like rails,  the  diagonal  method  for  beams  is  far  superior  to  the  older  flat 
method,  because  the  oblique  design  of  the  passes  makes  it  possible  to  secure  a 
much  greater  length  of  flange  than  was  ever  produced  by  the  first  method. 
This  advantage  is  forcibly  illustrated  in  the  steel  tie  section,  the  rolling  of 


STRUCTURAL  SHAPES 


465 


which  was  first  successfully  accomplished  at  Homestead.     This  section  with 
its  very  thin  flange,  which  has  almost  no  taper,  would  have  been  looked  upon, 


FIG.  88.     Methods  of  Rolling  Beams. 


FIG.  89.     Methods  of  Rolling  Piling. 


fifteen  years  ago  as  an  impossibility  from  a  rolling  standpoint,  and  is  con- 
sidered one  of  the  greatest  achievements  in  roll  design.     U.  S.  steel  piling 


466  THE  ROLLING  OF  SECTIONS 

is  another  section  which  much  resembles  the  rail  in  rolling.  Here,  the  ball 
and  web  of  the  piling,  as  finished,  is  almost  a  duplicate  of  the  head  and  web 
of  the  rail,  and  the  remainder  is  rolled  as  a  flange  up  to  the  leading  and 
finishing  passes,  when  the  two  halves  or  legs  are  bent  down  to  form  the 
socket  for  the  interlock.  It  is  rolled  either  by  the  flat  or  diagonal  methods. 

Zees  and  Tees :  Zees  may  be  looked  upon  as  double  angles  or  channels 
with  reversed  legs,  or  flanges,  and  the  methods  of  rolling  correspond  to  the 
first  two  methods  for  angles.  As  to  tees,  it  is  doubtful  if  any  other  section 
offers  as  little  opportunity  for  variation.  There  is  only  one  way  by  which 
the  tee  can  be  rolled.  In  this  method  the  shaping  begins  from  a  square  bil- 
let or  bloom.  One  side  of  the  square  is  retained  to  form  the  base,  or  table, 
of  the  tee,  while  the  edges  of  the  opposite  side  are  both  recessed  in  the 
first  forming  pass  by  collars  on  each  side  of  a  groove  into  which  part  of 
the  metal  flows  to  start  the  stem.  The  piece  is  then  edged  for  the  next 
pass,  in  which  the  stem  is  reduced  between  the  flat  surfaces  of  the  rolls, 
while  the  two  parts  of  the  table  pass  through  grooves  in  the  two  rolls. 
In  the  next  pass  the  piece  is  turned  with  the  stem  up,  which  will  pass 
through  an  idle  groove,  while  the  table  on  each  side  of  the  stem  will  be 
reduced  between  the  plain  surfaces  of  the  rolls.  This  process  is  then 
repeated,  the  piece  being  worked  alternately  on  the  stem  and  table,  until 
the  section  reaches  the  size  desired  in  the  finishing  pass.  Usually,  in  this 
last  pass  the  stem  is  in  the  groove  of  the  lower  roll  and  the  table  is 
reduced  between  the  rolls.  In  order  to  prevent  the  bar  from  following  the 
roll  on  the  delivery  side,  this  groove,  as  for  all  the  idle  grooves,  must  taper 
slightly  from  the  top  and  be  large  enough  to  give  easy  passage  for  the  stem, 
thus  making  it  somewhat  wider  than  the  stem  is  thick.  The  reduction  of 
the  table  then  results  in  the  formation  of  a  slight  overfill  at  the  base  of  the 
stem.  This  bit  of  excess  metal  cannot  be  removed,  because  the  stem  was 
necessarily  finished  in  the  preceding,  or  leading,  pass.  If  the  section  were 
finished  by  working  on  the  stem,  the  same  defect  would  be  developed. 

Finishing  Sections:  Most  shape  mills  are  provided  with  hot  saws 
located  after  the  finishing  pass  and  near  the  cooling  beds.  These  saws  are 
intended  mainly  for  cutting  test  pieces,  but  in  some  mills  they  are  used 
for  cutting  off  crop  ends  or  dividing  mill  lengths  where  the  cooling  beds 
are  too  short  to  take  full  mill  lengths.  The  test  pieces  are  of  two  kinds, 
namely,  those  for  the  roller,  whose  duty  it  is  to  see«that  the  section  is  rolled 
to  the  correct  dimensions  and  weight,  and  those  for  the  physical  laboratories. 
With  these  exceptions,  however,  the  full  mill  length  is  sent  directly  to  the 
cooling  bed.  Here,  as  in  the  case  of  rails,  the  cooling  causes  the  shapes 
to  bend  considerably,  and  cold  straightening  is  necessary.  For  this  purpose, 
the  piece  is  next  passed  through  a  cold  roll  straightening  machine,  and  if 
necessary  through  a  gag  press.  The  roll  straightener  is  capable  of 
straightening  in  one  direction  only,  so  that  if,  through  handling  or  other 
cause,  the  piece  has  been  twisted  or  bent  laterally,  it  can  be  made  straight, 


ROUNDS 


467 


in  all  directions,  only  by  using  a  gag  press  after  the  roll  straightener.  From 
the  straighteners  the  material  passes  the  cutting  machines,  which,  in  order 
to  keep  up  with  the  mill,  must  be  either  shears  or  cold  saws.  For  this 
reason,  exact  cutting  to  length  is  out  of  the  question,  and  a  liberal  cutting 
tolerance  is  always  desired  by  the  mill.  As  a  rule,  angles,  zees  and  small 
tees  are  sheared,  while  channels,  beams  and  large  tees  are  cut  with  cold 
saws.  During  the  cutting,  any  material  that  contains  the  more  noticeable 
defects  is  discarded  and  cut  into  scrap  lengths,  and  after  the  cutting  the 
material  is  subjected  to  a  very  rigid  inspection  for  the  most  minute  surface 
defects. 

Rounds:  In  the  steel  business,  rounds  are  often  designated  as  hand 
rounds  or  guide  rounds,  and  these  terms  are  indicative  of  the  two  methods 
for  rolling  these  shapes.  In  the  first  method,  the  bloom  or  billet  is  first 
reduced  in  diamond  shaped  roughing  passes  to  the  form  of  a  round  cornered 
square.  Then,  by  means  of  tongs  in  the  hands  of  the  workmen,  this  square 
is  supported  in  the  correct  positions  and  passed  through  a  single  round- 
forming,  oval-shaped  pass,  or  two  similar  round-forming  passes,  until  it  has 
been  worked  into  the  round  form,  which  can  be  accomplished  by  turning 


Billet 


Bounds 


FIG.  90.     Rolling  a  Half  Inch  Guide  Round. 


the  piece  through  an  angle  of  90°  after  each  pass  through  the  rolls.  From 
three  to  five  passes  in  the  finishing  stand  are  required  to  form  the  round 
by  this  method  of  rolling.  In  the  case  of  guide  rounds  the  size  of  the  billet 
may  be  reduced  in  the  roughing  passes  in  a  manner  similar  to  that  for  hand 
rounds,  or  by  any  other  method  that  will  give  a  round  cornered  square. 
This  square  is  then  reduced  in  one  or  two  passes  to  an  oval,  which  is  then 
edged,  and  while  supported  in  this  position  by  a  guide,  it  is  put  through 
a  round  finishing  pass.  The  compression  in  this  pass  shortens  the  long 
axis,  while  the  spreading  of  the  metal  lengthens  the  short  axis  of  the  oval 
to  equal  the  radii  of  the  round.  In  a  general  way,  large  rounds,  that  is, 
those  over  two  inches  in  diameter,  are  rolled  by  hand,  while  small  rounds, 


THE  ROLLING  OF  SECTIONS 


less  than  two  inches  in  diameter,  are  rolled  with  guides,  but  there  is  a 
narrow  range  from  about  one  and  three-fourths  inches  to  two  and  one-half 
inches  where  either  method  may  be  employed.  Regarding  the  relative 
merits  of  these  two  methods,  hand  rounds  are  by  many  preferred  to  guide 
rounds  where  great  accuracy  and  uniformity  in  diameter  are  required. 
However,  guide  rounds  are  now  rolled  with  a  high  degree  of  accuracy,  and 
since  the  uniformity  and  accuracy  of  the  hand  rounds  depends  on  the  skill 
of  the  workmen,  it  is  doubtful  whether  equal  care  and  attention  applied 
to  both  methods  would  leave,  on  the  average,  much  wherewith  to  choose 
between  them. 

Cutting  and  Straightening  Rounds:  In  order  to  keep  up  with  the 
mills,  rounds  are  either  hot  sawed  or  cold  sheared  to  convenient  lengths, 
and  neither  method  is  at  all  exact.  Hence,  in  these  lengths,  either  single 
or  multiples  of  those  desired,  proper  allowance  must  be  made  for  the  exact 
cutting,  which  is  performed  by  special  cutting  machines  after  the  round  is 
straightened.  The  straightening  may  be  done  either  on  the  gag  press  or 
on  special  straightening  machines,  called  from  the  inventors  the  Brightman 
and  Abramsen  straighteners.  The  Brightman  consists  of  two  rows,  or  sets, 
of  concave  rolls  mounted  upon  opposite  sides  of  a  revolving  frame,  so  that, 
with  their  axis  of  rotation  at  an  angle  to  that  of  the  frame,  the  concave 
surfaces  of  opposite  rolls  bear  on  the  round  and  grip  it  in  such  a  manner  as 
to  force  the  bar  along  longitudinally  and  at  the  same  time  bend  it  at  the 
crooked  places  enough  to  straighten  it.  In  the  other  type  of  machine  the 
rolls  are  mounted  on  a  stationary  frame,  while  the  piece  itself  is  revolved 
and  forced  through  it.  The  straightening  develops  one  serious  defect, 
which  renders  the  bar  unsuitable  for  some  purposes.  The  scale  in  the  spiral 
path  of  the  rolls  is  rolled  into  the  surface,  causing  a  slight  pitting,  which 
can  be  removed  only  by  machining. 

Flats  :  Because  they  are  the  simplest,  the  flats  were  the  first  sections 
to  be  rolled.  The  main  problem  involved  in  designing  the  rolls  for  flats  is 
the  control  of  the  width,  which  is  done  in  two  ways  after  the  piece  has  left 
the  roughing  rolls.  The  first  method,  called  the  flat  and  edging,  consists 
merely  of  rolling  the  piece  on  edge  at  intervals  in  deep  grooves  cut  in  the 
roils.  The  other  method  of  controlling  the  width  lies  in  the  use  of  the 
tongue  and  groove  passes  as  described  under  the  rolling  of  sheet  bars,  and 
is  best  suited  to  the  rolling  of  thin  material.  In  this  method  the  last  two 
passes  will  be  between  plain  rolls,  while  in  the  flat  and  edging  method  the 
planisher  will  be  an  edging  pass.  It  is  in  this  pass  that  the  three  different 
edges  on  flats  are  formed.  Thus,  if  the  bottom  of  the  groove  is  flat,  a 
common  swell  or  oval  edge  will  be  formed  by  the  spreading  of  the  material 
in  the  center,  which  is  hotter  than  the  outside;  but  if  the  base  of  this  groove 
is  made  sufficiently  concave,  the  edge  of  the  bar  will  be  round;  if  convex,  a 
square  edge  will  be  formed.  In  the  eighteen  inch  mill  at  Clairton  and  also 
in  the  fifteen  inch  mill  at  Lower  Union  City  Mills  there  is  used,  next  to  the 
finishing  pass,  a  set  of  vertical  rolls,  which  eliminates  the  difficulty  of 
rolling  a  wide  thin  flat  in  an  ordinary  groove. 


HEXAGONS  AND  DEFORMED  BARS  469 

Hexagons :  There  are  two  methods  used  for  rolling  hexagons.  By  one 
method  all  six  corners  are  formed  in  the  rolls,  three  in  the  top  and  three  in 
the  bottom.  The  clearance  between  the  rolls  in  this  case  comes  on  opposite 
flat  surfaces  of  the  bar.  In  this  manner  of  rolling,  the  corners  of  the  hexagon 
cannot  pinch  out.  Hexagons  rolled  thus  are  best  suited  for  cold  drawing 
purposes  as  they  will  be  free  from  pinches  which  draw  out  into  laps.  In  this 
method,  the  first  pass  in  the  strand,  or  first  former,  is  a  square  which  has 
been  broken  down  from  the  billet  in  the  roughing  and  pony  roughing  stands. 
The  square  is  then  put  into  the  second  strand,  or  former,  and  comes  out 
in  the  form  of  a  six  sided  flat,  the  two  widest  sides  of  which  are  convex. 
The  bar  is  then  edged  into  the  leading  or  planishing  pass  where  a  reduction 
of  about  25%  takes  place,  in  the  case  of  small  hexagons.  The  bar  coming 
out  of  tins  pass  has  six  sides  as  before  but  has  two  of  its  corners  formed 
by  the  clearance  of  the  rolls.  The  top  and  bottom  sides  are  slightly  concave 
to  allow  for  the  spread  as  the  bar  is  edged  into  the  finishing.  Here  the 
bar  is  given  a  light  draft,  in  order  to  square  it  up,  the  reduction  being  only 
8  to  10%. In  the  other  method  two  of  the  corners  of  the  finished  bar  are 
formed  at  the  clearance  of  the  rolls,  and  hence  care  must  be  taken  to  keep 
these  corners  from  pinching  out.  The  bar  coming  out  of  the  planishing  in 
this  method,  is  in  the  same  position  as  the  finished  bar  of  the  first  method. 
The  bar  is  turned  90°  and  entered  into  the  finishing  so  that  its  top  and 
bottom  surface  are  flat  or  horizontal  and  two  of  its  corners  are  in  the 
clearance  between  the  rolls.  In  the  one  method  but  three  passes  are 
required  to  form  the  finished  bar  from  the  square  while  the  other  method 
requires  four. 

i 

Deformed  Bars:  This  term  is  meant  to  include  any  bar  having  an 
irregular  surface  or  a  surface  on  which  there  are  projections  or  depressions, 
such  as  the  various  concrete  reinforcing  bars,  clip  iron,  hame  strap,  etc. 
Some  of  these  bars  are  so  complex  as  to  excite  the  highest  admiration  and 
astonishment  from  those  not  familiar  with  their  manufacture.  While  they 
require  the  greatest  ingenuity  on  the  part  of  the  roll  designer,  they  are, 
however,  produced  with  less  difficulty  than  might  be  supposed.  Briefly, 
the  secret  of  their  formation  consists  in  first  working  the  metal  down  through 
the  ordinary  passes  to  one  of  the  common  forms,  such  as  a  flat,  square, 
round,  or  oval,  whichever  is  best  for  forming  the  bar  desired,  and  then 
putting  it  through  one  or  two  deforming  grooves  containing  the  necessary 
recesses  or  elevations.  It  is  here  the  chief  trouble  occurs.  As  the  deforma- 
tions must  be  made  in  the  finishing  pass,  or  the  leader  and  finishing  com- 
bined, a  heavy  draught  in  these  passes  is  necessary,  and  the  metal  is  usually, 
even  with  the  fastest  working,  at  a  very  low  temperature  for  working, 
These  conditions  put  a  heavy  strain  on  the  mill,  and,  owing  to  the  lack 
of  plasticity  in  the  metal,  the  projections  will  not  fill  out  easily.  In  order 
to  avoid  vibrations  which  cause  the  bar  to  slip  in  passing  through  the  rolls, 
thus  causing  the  deformations  to  be  made  at  irregular  intervals,  mills 
rolling  these  sections  are  provided  with  separately  driven  finishing  stands 


470  THE  ROLLING  OF  STEEL 


CHAPTER  IX. 

THE  ROLLING  OF  STRIP  AND  MERCHANT  MILL  PRODUCTS 

SECTION   I. 

STRIP,   OR   HOOP,   MILLS  AND   THEIR  PRODUCTS. 

Meaning  of  the  Word  Hoop:  As  originally  applied,  the  word  hoop 
meant  that  light  narrow  material  which,  cut  into  short  lengths,  was  used 
to  bind  casks,  barrels,  buckets,  and  the  like,  but  as  now  employed  the 
word  is  a  class  name  that  stands  for  a  large  number  of  products.  The 
Carnegie  Steel  Company,  for  instance,  uses  the  term  to  cover  all  materials 
from  13  gauge  to  the  thinnest  material  rolled  on  their  mills,  and  from  three- 
eighths  inch  to  eight  and  five-eighths  inches  in  width.  This  range  covers 
material  used  for  a  great  variety  of  purposes  in  addition  to  hoop,  such  as 
skelp  for  tubes,  blades  for  knives,  and  blanks  for  stamping  hundreds  of 
hardware  specialties,  a  class  of  material  that  should  represent  a  little  better 
grade  than  ordinary  hoop.  In  a  way,  this  use  of  the  word  hoop  is  unfortu- 
nate, especially  as  a  more  suitable  class  name  is  supplied  by  the  term  strip. 
With  strip  for  a  class  name,  hoop  would  have  retained  its  original  meaning, 
for  which  there  is  no  substitute,  and  all  danger  of  ambiguity  would  have 
been  avoided. 

Hoop  as  a  Rolling  Specialty:  Being,  perhaps,  the  largest  pro- 
ducer of  strip  in  the  country,  the  Carnegie  Steel  Company's,  mills  furnish 
the  best  example  of  the  equipment  and  organization  required  to  roll  this 
class  of  material.  A  specialty  mill  is  not  a  mill  that  rolls  a  specialty 
nor  a  variety  of  specialties,  but  one  that  has  specialized  in  the  rolling  of 
a  single  product.  According  to  this  definition,  and  using  the  term  hoop 
in  its  broad  sense  as  outlined  in  the  preceding  paragraph,  the  hoop  mills 
of  this  company  are  best  described  as  specialized  specialty  mills,  because 
they  are  laid  down,  not  for  the  general  purpose  of  rolling  hoop  or  strip,  but 
in  such  a  manner  that  each  mill  is  designed  and  equipped  to  roll  a  certain 
kind  or  grade  of  hoop.  The  advantage  of  such  a  system  is  at  once  evident, 
making  it  possible  for  the  mills  to  meet  the  many  demands  of  the  trade 
most  readily.  Thus,  they  are  able  to  give  accuracy,  where  accuracy  is 
required;  finish,  where  finish  is  desired;  quantity,  where  quantity  is  the 
main  consideration;  and  all  with  a  better  quality  to  the  customer  and  at 
a  greater  saving  to  the  producer  than  would  be  possible  in  any  other  way. 

The  Carnegie  Hoop  Mills:  From  what  has  just  been  said,  it  will 
readily  be  surmised  that  the  hoop  mills  of  this  company  are  many  in  number 
and  of  various  types,  and  no  detailed  description  of  all  of  them  can  be 


HOT  STRIP  OR  HOOP  471 


expected.  This  excuse  will  be  better  appreciated  when  it  is  known  that 
their  hoop  mills  number  no  less  than  twenty-five,  and  among  these  at  least 
six  types,  or  designs,  of  mill  are  represented.  However,  these  mills  present 
certain  features  of  a  general  nature,  for  the  omission  of  which  no  valid 
excuse  can  be  found.  In  size  their  hoop  mills  range  from  seven  to  twelve 
inches,  the  most  common  size  being  eight  and  ten  inches.  In  some  of  the 
mills  the  different  stands  of  rolls  will  vary  in  size.  Thus  in  the  McCutcheon 
No.  6  Mill,  eleven  inch  rolls  are  employed  in  the  roughing  stands,  nine 
inch  in  the  intermediates,  and  eight  inch  in  the  planisher  and  finisher. 
The  rolls  may  be  of  different  sizes  in  the  same  stand,  also,  as  will  be  explained 
later.  As  to  the  materials  of  which  the  rolls  are  made,  the  roughing  rolls 
may  be  of  steel  and  the  intermediates  of  sand  or  adamite,  but  the  finishing 
rolls  are  always  of  the  hardest  chilled  iron.  The  number  of  stands  in  these 
milts  vary  from  eight  to  twelve  per  mill,  and  their  arrangement  is  such  as 
to  produce  the  kind  of  hoop  desired  to  best  advantage,  as  will  be  more 
clearly  explained  later. 

Methods  of  Rolling  Hoop :  While  hoop  of  the  heavier  and  medium  gauges 
and  narrower  widths  is  successfully  rolled  by  the  flat  and  edging  method, 
it  is  readily  understood  that  this  method  is  not  applicable  to  all  sizes  of 
hoop.  After  the  material  leaves  the  roughing  rolls  there  is  but  one  way 
remaining,  then,  by  which  it  can  be  reduced,  and  that  is  by  the  tongue  and 
groove  method  already  described.  These  tongue  and  groove  passes  will  be 
found  to  be  three  or  four  in  number,  though  only  two  are  used  in  some  of 
th6  mills,  and  to  be  followed  by  two  or  three  stands  of  plain  rolls.  As  to 
the  manner  of  breaking  down  in  the  roughing  stands,  there  are  two  methods 
of  rolling — one  in  which  the  billet  is  reduced  by  flat  and  edging  passes  and 
another  in  which  the  roughing  passes  are  ovals  and  squares.  The  latter 
method  gives  a  more  rapid  reduction,  and  will  be  employed  usually  where 
only  two  roughing  stands  precede  the  tongue  and  groove  rolls. 

Precautions  Required  in  Rolling  Hoop:  The  chief  difficulty 
encountered  in  rolling  this  light  strip  lies  in  getting  the  hoop  through  the 
rolls  before  it  becomes  too  cold  to  roll,  or  in  keeping  the  temperature 
uniform  at  the  finishing  roll,  which  is  necessary  to  produce  a  strip  uniform 
in  gauge.  Considering  the  rapidity  with  which  the  metal  is  cooled  on 
account  of  the  thin  section  and  the  chilling  effect  of  the  cold  rolls,  the 
accuracy  as  to  gauge  and  width  maintained  by  the  hoop  mills  is  little 
short  of  astonishing.  In  this  case  the  ingenuity  of  the  engineer  who  builds 
the  mill  and  that  of  the  roll  turner  who  designs  the  rolls  are  both  required, 
in,  addition  to  the  skill  of  the  rollers,  to  produce  the  desired  result.  By 
reducing  the  number  of  passes  to  a  minimum  in  the  ways  already  described, 
the  roll  designer  has  done  his  bit,  but  even  then  the  last  end  of  a  long  strip 
will  be  cooled  to  a  temperature  so  much  lower  than  the  first  that  it  will 
finish  several  thousandths  of  an  inch  thicker,  unless  the  mill  is  adapted  to 
rolling  it.  These  drawbacks  are  overcome  by  a  combination  of  ingenious 


472  THE  ROLLING  OF  STEEL 


schemes.  First,  the  mill  is  run  at  as  high  a  speed  as  practicable.  Second, 
it  is  arranged  and  operated  so  that  as  little  time  as  possible  intervenes 
between  passes.  Thus,  in  the  more  modern  hoop  mills,  roughing  rolls  on 
the  continuous  plan  are  used,  and  these  are  placed  very  close  to  the  furnace, 
whence  the  billet,  being  at  once  reduced  in  the  two  or  three  roughing  passes, 
passes  over  roll  tables  to  the  tongue  and  groove  rolls,  which  are  arranged 
on  the  continuous  plan  or  in  train.  If  the  latter  plan  is  followed,  mechanical 
repeaters  are  employed  for  short  lengths,  or  the  piece  is  looped  from  pass 
to  pass  by  hand,  by  which  means  it  may  be  rolling  in  two  or  more  stands 
at  one  time.  In  order  to  avoid  having  the  loop,  which  increases  with  the 
length  of  the  piece,  run  far  out  on  the  floor,  and  thus  become  chilled,  each 
pass  following  the  tongue  and  groove  passes  is  made  to  run  as  much  faster 
as  its  predecessor  as  is  necessary  to  take  up  the  slack  due  to  the  elongation. 
Other  schemes  to  equalize  the  finishing  temperature  are  also  employed. 
It  is  said  that  at  some  hoop  mills  the  end  of  the  billet  which  represents 
the  last  end  of  the  hoop  to  pass  through  the  rolls  is  heated  to  a 
higher  temperature  than  the  first  end.  In  the  cotton  tie  mill  at  Youngs- 
town,  where  the  strips  are  about  1800  feet  in  length,  one  end  of  the  billet 
will  be  in  the  furnace,  while  the  other  will  be  coiling  some  200  feet  away 
at  the  other  end  of  the  mill  as  finished  strip.  Other  factors  affecting  the 
uniformity  of  gauge,  or  thickness,  are  the  wear  of  the  rolls  and  the  bearings. 
To  overcome  the  wear  of  the  former,  which  also  affects  the  finish,  the 
path  of  the  piece  through  the  leading  and  finishing  passes  is  moved  over 
to  a  new  surface  about  every  twenty  minutes,  or  whenever  these  surfaces 
become  too  rough.  The  vibration  of  the  mill  pinions  produces  waves 'or 
slip  marks  on  the  surface,  if  the  last  stands  are  in  train  with  the  tongue 
and  groove  rolls,  hence  the  planishing  and  finishing  rolls  are  generally 
separately  driven  in  mills  rolling  the  best  grades  of  hoop,  and  only  one 
of  the  rolls  is  driven,  the  other  revolving  by  friction  due  to  contact 
with  the  driven  roll.  The  planisher  may.  be  in  train  with  the  tongue  and 
groove  rolls,  but  the  finishing  stand  is  almost  always  separately  driven. 
At  some  of  the  mills  where  the  finisher  or  planisher,  or  both,  is  in  train 
with  the  rest  of  the  stands,  the  bottom  roll  is  much  larger  in  diameter 
than  the  top  roll  or  the  rest  of  the  mill,  and  is  driven,  while  the  top  roll 
revolves  by  friction.  The  larger  diameter  of  the  bottom  roll  increases  the 
speed  of  delivery  of  the  stand.  The  finish  on  some  hoop  is  of  great  im- 
portance. To  provide  for  this  requirement  scrapers  are  employed  in  front 
of  the  chill,  or  finishing,  rolls.  These  scrapers  consist  of  two  horizontal 
bars  spaced  about  eight  inches  apart  and  fixed  parallel  to  and  just  in  front 
of  the  rolls,  and  of  two  other  bars  similarly  arranged  but  fastened  to  the 
two  prongs  of  a  fork  that  can  be  moved  up  and  down  by  means  of  a  lever. 
In  this  way  the  movable  bars  can  be  lowered  as  desired  into  the  spaces 
between  the  fixed  bars  and  the  rolls.  As  soon  as  the  rolls  grip  the  piece 
the  scraper  is  brought  into  action,  and  the  piece  is  bent  sharply  up  and 
down  over  its  edges,  thus  cracking  the  scale  and  removing  it  at  once.  As 


HOT  STRIP  OR  HOOP  473 

the  piece,  after  coming  out  of  the  finishing  pass,  is  near  or  below  the  critical 
temperature,  no  more  scale  is  formed,  and  a  smooth  bluish  surface  results. 
About  five  or  six  feet  of  hoop  on  the  front  end  is  not  thus  scraped,  because 
the  great  speed  of  the  piece  carries  it  through  this  distance  before  the 
scraper  can  be  brought  into  play.  In  order  to  eliminate  this  unfinished 
end  with  as  little  waste  as  possible  the  shears  are  located,  preferably,  at 
the  mill  end  of  the  cooling  bed,  so  that  this  end  of  the  strip  is  the  last 
to  be  cut.  The  adjustment  of  the  rolls  is  also  an  important  matter  in 
rolling  hoop.  To  illustrate  this  point,  if  one  of  the  finishing  rolls  is  enough 
out  of  level  to  make  a  difference  of  only  one-ten-thousandth  of  an  inch  in 
the  thickness  of  the  hoop  on  its  edges,  it  will  bend  toward  the  heavy  side 
in  leaving  the  pass  an  amount  equal  to  one  foot  in  thirty  feet  of  length. 
As  the  stiffness  of  an  ordinary  hoop  is  only  sufficient  to  push  it,  even  on  a 
very  smooth  run  out,  a  distance  of  about  thirty  feet,  some  means  of  cheaply 
delivering  the  strip  away  from  the  last  stand  of  rolls  must  be  used.  In 
Carnegie  mills,  this  delivery  is  accomplished  in  three  ways,  namely,  by 
hot  coilers,  by  conveyor  belts  in  the  runouts,  or  by  pneumatic  runouts. 
In  the  last  named  type  of  conveyor,  air  blown  at  high  pressure  through 
holes  in  the  bottom  of  the  runout  and  at  angles  directed  away  from  the 
mill,  lifts  the  strip,  decreases  the  friction  and  helps  to  carry  it  along. 

Finishing  Hoop:  Hoop  may  be  finished  in  many  ways.  As  to  the 
cutting  of  hoop,  it  is  always  cold  sheared,  and  this  may  be  done  so  as  to 
give  either  both  ends  square  or  one  end  square  and  one  end  round.  For 
this  kind  of  cutting,  a  special  die  with  a  double  edge,  one  round,  the  other 
square,  is  used,  and  the  shapes  on  the  ends  of  the  hoop  are  formed  by 
punching  out  a  small  part  of  the  hoop.  Ordinary  hoop,  not  coiled,  is  cut 
on  alligator  or  small  guillotine  shears,  but  the  cotton  tie  mill  is  equipped 
with  two  shears  of  a  special  type,  which  consists  of  two  revolving  wheels 
on  each  of  which  a  shear  knife  is  mounted.  By  regulating  the  relative 
speeds  of  the  wheels,  these  shear-blades  are  brought  together  in  every  so 
many  revolutions,  so  that  as  the  strip  is  fed  into  the  shear  at  a  definite 
speed,  it  is  cut  into  approximately  equal  lengths.  Anything  near  exact 
cutting  is  impossible  on  this  machine,  due  to  slipping  of  the  belts  and  the 
play  in  the  parts  of  the  machine.  Flaring  and  punching  machines  are 
provided  at  some  of  the  mills,  and  in  this  connection  it  is  to  be  remembered 
that  the  flare  on  a  hoop  is  measured  correctly  by  one-half  the  difference 
between  the  largest  and  smallest  diameters.  All  three  methods  of  bundling, 
in  strips,  in  scrolls  and  in  coils,  are  practiced.  As  to  coils,  some  of  the  mills 
can  coil  in  multiple  or  single  strips,  while  others  can  coil  only  in  singles. 
Hot  coiling  can  be  done  only  at  certain  mills,  also.  It  is  a  matter  of  pride 
with  the  men  at  the  mills  to  turn  out  the  finest  product,  and  any  order 
that  calls  for  extra  quality  and  finish  is  sure  to  receive  the  attention  it 
deserves.  On  such  material  special  tests,  such  as  the  acid  test  for  scale 
pits  and  bending-over  tests  for  seams,  are  often  made  in  addition  to  the 
ordinary  inspection  for  surface  defects  and  gauging  for  thickness  and  width. 


474 


THE  ROLLING  OF  STEEL 


SECTION   II. 

MERCHANT  MILLS. 

What  the  Merchant  Mill  Is:  The  first  mills  were  what  we  of  to-day 
would  call  merchant  mills,  though  the  term  was  perhaps  not  then  applied 
to  them.  In  the  beginning  of  the  industry,  all  mills  doubtless  rolled  a 
variety  of  simple  sections  such  as  rounds,  squares,  flats,  etc.,  but  as  the 
business  grew  and  the  demand  for  heavier  material  and  for  certain  shapes 
increased,  mills  designed  to  meet  a  given  demand  or  to  roll  a  certain  kind 
of  product  began  to  appear.  Then  it  was  that  the  smaller  or  older  mills, 
which  continued  to  roll  a  variety  of  sections  and  often  stocked  material 
that  was  retailed  out  later,  were  designated  as  merchant  mills,  in  order  to 
distinguish  them  from  the  specialty  mills  and  those  whose  product  was 
handled  in  large  lots.  Later  on,  especially  in  this  country,  the  mill  manner 
of  handling  materials  and  doing  business  underwent  a  change,  and  the  mills 
were  more  or  less  divorced  from  the  store  house,  so  that  these  mills,  while 
they  continue  to  roll  a  variety  of  sections,  always  roll  to  orders.  Thus, 
though  they  have  lost  all  the  characteristics,  they  still  retain  the  name  of 
merchant  mills.  Therefore,  in  this  country  a  merchant  mill  is  any  small 
mill,  say  twenty-two  inches  and  under,  which  regularly  produces  more  than 
one  shape. 

Kinds  of  Merchant  Mills:  In  touring  the  various  works,  the  visitor 
is  surprised  and  often  not  a  little  confused  by  the  great  number  of  and 
seemingly  meaningless  terms  applied  to  these  mills.  Thus,  there  is  heard 

the  term  "barmill"  applied  to  two 
mills  of  altogether  different  types. 
The  term '  'guide  mill' '  is  apparently 
used  in  the  same  way.  Added  to 
these  are  such  names  as  ''Morgan 
mill,"  loop  mill,  shape  mill,  con- 
tinuous mill,  and  semi-continuous 
mill,  hoop  mill,  Belgian  mill,  com- 
bination mill,  etc.,  and>  such  local 
terms  as  the  "iron  mill,"  and  the 
"steel  mill,"  the  "electric  mill," 
or  just  "merchant  mill,"  as  at  one 
of  our  own  plants  where  there  is 
but  one  merchant  mill.  While  one 

not  familiar  with  the  mills  is  inclined  to  think  most  of  these  names  are 
accidental  localisms,  many  of  them  are  really  descriptive  of  the  mills  and 
also  form  links  in  a  systematic  classification  based  mainly  on  construction 
and  design.  These  terms  and  the  classification  of  the  mills  is  best 
explained  from  a  historical  viewpoint.  For  this  reason  it  is  desirable  to 
trace  very  briefly  the  evolution  of  the  small  mill. 


Plan 


Elevation 
FIG.  91.      First  Merchant  Rolling  Mill. 


MERCHANT  MILLS 


475 


Development  of  Merchant  Mills:  The  first  mill,  which  also  stands 
for  the  simplest  kind  of  mill,  consisted  of  a  single  stand  of  rolls  driven  in 
one  direction  only,  and  for  many  years  all  bars  or  sections  were  rolled  on 
this  simple  mill.  No  guides  were  used  at  first,  and  the  roller  guided  and 

supported  the  bar  between  the  rolls 
by  means  of  tongs.  In  order  to 
avoid  the  labor  of  pulling  the  bar 
around  the  mill,  the  catcher  re- 
turned it  by  laying  one  end  on  the 
top  roll,  which  carried  the  piece 
forward  with  little  effort  on  the 
catcher's  part.  To  avoid  this  idle 
pass,  the  idea  of  placing  a  third 
roll  above  the  second,  so  as  to 
work  the  bar  as  it  passed  in  both 
directions,  was  conceived  and  re- 
sulted in  a  great  economy  in  labor. 
Up  to  this  point  the  bars  were  com- 
paratively short,  sixteen  to  twenty 
feet  being  the  usual  lengths.  It 
was  next  discovered  that  a  great 
saving  in  both  labor  and  material 
could  be  effected  by  making  the 
Pia.  92.  Diagram  of  a  Simple  Type  of  bars  longer,  but  to  accomplish  this 
Three-High  Merchant  Mill.  increase,  a  larger  billet  had  to  be 

used.  The  increase  in  the  size  of  the  billet  was  secured  by  increasing  its 
length,  which  required  wide  heating  furnaces,  and  by  increasing  the  size  of 
its  cross  section,  which  called  for  a  greater  number  of  passes  for  reducing 
than  could  be  placed  in  one  stand.  To  supply  these  extra  passes,  addi- 
tional roll  stands  were  needed.  These  stands  were  coupled  together  to 
form  the  roll  train  of  Figure  92. 


The  Guide  Mill:  The  rolling  of  rounds,  which  have  always  been  an 
important  product,  led  to  the  first  use  of  guides.  The  method  first  used 
was  like  the  method  for  hand  rounds  previously  referred  to,  but  a  greater 
number  of  passes  were  used  to  finish  the  piece.  Since  the  tonnage, 
especially  on  small  rounds,  was  held  down  by  the  time  consumed  in  passing 
the  piece  back  and  forth  through  the  finishing  groove,  it  was  natural  that 
the  mill  man  should  seek  some  way  of  reducing  the  number  of  these  passes. 
This  endeavor  led  to  a  really  great  discovery,  namely,  that  a  round  could  be 
rolled  in  one  pass  from  an  oval,  provided  the  oval  was  of  the  right  dimensions 
and  was  supported  by  metal  guides.  This  success  of  the  guide  led  to  its 
use  for  other  shapes,  also,  and  to  its  adoption  in  modified  forms  to  nearly 
all  mills.  Thus,  another  word,  guide,  came  to  be  rather  loosely  used.  In 
general,  a  guide  is  any  device  used  to  support  the  piece  in  the  correct 
position  during  its  passage  through  the  groove.  In  order  to  perform  this 


476 


THE  ROLLING  OF   STEEL 


function,  the  guide  must  fit  neatly  against  the  roll  or  rolls,  so  one  end  must 
be  shaped  to  conform  to  the  shape  of  the  space  in  front  of  the  rolls. 
Entering  guides  are  usually  of  the  closed  type.  They  are  made  in  two  parts. 


Rougher 


Heating 
Furnace 


Hot  Bed 


<§& 


Engine 


FIG.  93.     General  Layout  for  an  Eight  Inch  Guide  Mill — Belgian  Type. 


In  each  of  these  two  parts  a  groove  is  cut  parallel  to  its  long  axis,  so  that 
when  the  two  parts  are  fitted  together  the  opening  formed  by  the  grooves 


MERCHANT  MILLS 


477 


will  be  of  the  required  shape  of  section  to  support  the  piece  properly.  The 
guide  proved  to  be  of  immense  advantage  in  another  way,  in  as  much  as  it 
permitted  the  rolling  of  very  long  lengths.  Today,  any  mill  designed  to 
roll  sections  that  require  the'use  of  guides  may  be  called  a  guide  mill. 

The  Belgian  and  Looping  Mills:  Though  it  was  now  possible  to 
roll  in  long  lengths,  a  serious  drawback  was  encountered  in  the  old  and 
slow-going  mill,  for,  if  the  piece  were  long  and,  especially,  if  the  section 
were  small,  the  steel  would  get  too  cold  to  roll  before  the  piece  could  be 
finished.  The  remedy,  of  course,  was  found  in  greater  speed,  but  here 
trouble  was  again  encountered  because  of  the  roughing  rolls  which  refuse 
to  bite  the  billet  if  the  speed  is  too  great.  Then  there  originated  in  Belgium 
the  scheme  of  setting  up  an  independent  roughing  stand  that  could  be  driven 

from  the  main  drive  shaft  of  the  en- 
/"*" ^        t  gine  at  a  lower  speed  than  the  finish- 

f      N\  i        1^         ing  train,  which  was  driven  by  power 

transmitted  by  belt  from  a  large 
pulley  on  the  drive  shaft  to  a  much 
smaller  one  mounted  on  a  short 
shaft  connected  with  the  train 
pinion.  Up  to  this  time  the  piece 
was  rolled  throughout  its  length 
in  a  given  pass  before  it  was 
started  into  the  next.  Who  the 
man  was,  or  what  his  degree,  that 
was  responsible  for  the  next  ad- 
vance in  rolling,  history  does  not 
say,  but  doubtless  it  was  some 

FIG.  94.  Early  Type  of  Looping  Mill.  bold  Belgian  catcher  who  first  con- 
ceived the  idea  of  catching  the  first  end  as  it  came  through  the  rolls  and 
returning  it  immediately  through  the  next  pass,  thus  rolling  the  section  in 
two  passes  at  once.  Since  the  speed  of  the  piece  on  the  delivery  side  is 
greater  than  that  of  the  rolls,  due  to  the  elongation,  the  material  overfed 
and  formed  a  loop.  By  this  looping  scheme,  the  capacity  of  the  finishing 
train  was  increased  beyond  that  of  the  roughing  stand. 


The  Semi-continuous  or  Combination  Mill:  Such  was  the  extent 
of  the  development  until  a  few  years  prior  to  1900,  when  two  things  com- 
bined to  force  another  advance  in  the  merchant  mill;  one  was  the  previous 
development  and  success  of  the  continuous  mill  as  a  semi-finishing  mill; 
the  other  was  the  necessity  for  economy  due  to  labor  troubles  and1  a  severe 
depression  in  the  steel  business.  So,  in  order  to  decrease  labor  costs  and 
speed  up  the  mill  to  the  limit  of  the  finishing  train,  the  continuous  rougher 
was  installed  to  replace  the  single  three-high  roughing  stand  of  the  Belgian 
mill.  By  this  inovation  the  mill  force  was  decreased  by  about  nine  men, 
while  the  output  was  increased  50%.  The  mill  proper  was  then  in  a  position 


478 


THE  ROLLING  OF  STEEL 

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MERCHANT  MILLS  479 


to  roll  in  unlimited  lengths  and  thus  effect  another  saving;  but  two  things 
combined  to  limit  the  length  of  the  piece  rolled,  namely,  the  difficulty  of 
handling  long  pieces  on  the  old  style  cooling  bed  and  the  problem  of  keeping 
the  bar  uniformly  hot  for  finishing.  The  first  problem  was  solved  by  the 
invention  of  the  mechanical  cooling  bed.  These  beds  consist  of  a  runout, 
in  which  are  live  rolls,  for  delivering  the  piece;  a  device  for  stopping  and 
transferring  the  material,  which  is  delivered  at  speeds  as  high  as  twenty- 
five  feet  per  second,  and  at  intervals  of  only  one  or  two  seconds  between 
pieces;  a  system  of  notched  or  fingered  racks,  by  means  of  which  the  hot  bars 
are  moved  away  from  the  runout;  and  a  receiving  table,  also  containing  live 
rolls,  by  means  of  which  the  bars  are  delivered  to  the  shears.  Examples 
of  these  tables  will  be  found  at  all  modern  mills.  The  problem  of  uniform 
heat  was  then  solved  by  speeding  up  the  mill;  by  locating  the  roughing 
rolls  near  a  continuous  furnace,  as  was  pointed  out  in  discussing  the  rolling 
of  hoops;  and  by  arranging  the  drive  of  the  mill  so  that  the  peripheral 
speed  of  the  rolls  is  increased  in  the  successive  passes  to  take  up  the  slack 
in  the  loops.  Another  device,  by  which  the  number  of  hands  employed 
about  the  mill  was  reduced,  is  the  mechanical  repeater.  Many  mills 
equipped  with  these  repeaters  are  entirely  automatic  in  operation  of  the 
rolls,  and  can  roll  material  that  is  much  too  stiff  to  be  turned  or  looped  by 
hand. 

The  Cross  Country  Mill :  While  these  improvements  were  being  made 
in  the  looping  mill,  a  mill  of  a  different  type  altogether  has  been  developed. 
It  is  known  as  the  cross-country  mill,  and  is  intended  for  rolling  material 
that  does  not  lend  itself  well,  on  account  of  size  or  shape,  to  loop  mill  rolling. 
These  mills  involve  the  continuous  idea,  but  the  stands  are  placed  so  far 
apart  that  the  piece  must  leave  one  set  of  rolls  before  entering  the  next. 
For  carrying  the  piece  from  stand  to  stand  stationary  roll  tables  are  em- 
ployed. To  save  space  and  avoid  complicating  the  drive  the  stands  may 
be  arranged  on  two  or  more  parallel  lines,  and  the  direction  of  travel  of 
the  piece  will  be  reversed  during  the  rolling.  Three-high  stands  are  placed 
at  the  reversing  points,  so  that,  by  means  of  mechanical  repeaters  and 
diagonally  placed  tables,  the  feeding  of  the  mill  is  made  automatic  through- 
out. In  the  latest  types  of  these  mills,  as  for  example  the  No.  7  mill  at 
Duquesne,  which  made  its  first  trial  rolling  in  July,  1917,  the  three-high 
stands  have  been  eliminated  and  two-high  substituted,  the  piece  being 
moved  over  from  the  first  roll  line  to  the  second  then  to  the  third  by  transfer 
and  skid  tables.  In  general,  the  tendency  is  to  return  to  the  two-high 
stand,  because  it  is  the  simplest  as  well  as  the  strongest  and  most  rigid 
in  construction. 

Future  Development:  From  the  preceding  sketch,  it  would  appear 
that  the  merchant  mill,  so  far  as  the  mill  is  concerned,  has  been  developed 
almost  to  the  highest  stage  of  perfection.  At  present,  the  trend  of  improve- 
ment is  in  two  directions,  one  looking  toward  economy  in  power  and  the 


480 


THE  ROLLING  OF  STEEL 


Heating  Furnace 


Heating  Furnace 


MERCHANT  MILLS 


481 


poq  8uijooo  oj. 


482  THE  ROLLING  OF  STEEL 

other  toward  specialization.  As  to  the  first,  the  adoption  of  electricity  for 
driving  the  mills  promises  to  effect  economies.  Much  advancement  has 
been  made  since  1900  in  the  construction  of  electrical  motors,  which,  through 
supplemental  equipment  such  as  rotating  resistors,  balancing  sets,  etc., 
have  reached  a  very  high  state  of  efficiency,  and  a  great  majority  of  the 
mills  installed  since  1916  are  equipped  with  these  motors.  Specialization 
is  taking  two  courses.  Thus,  more  and  more  specialty  mills  are  being 
erected,  and  other  mills  are  being  supplied  with  special  equipment,  such 
as  supplementary  roll  stands,  which  adapts  them  to  the  rolling  of  certain 
sections  yet  leaves  them  free  to  roll  other  products,  also. 

SECTION   III. 

DESIGNING   ROLLS   AND   MAKING   UP   SCHEDULES   FOR   MERCHANT   MILLS. 

Roll  Designing  for  Merchant  Mills :  It  does  not  require  much  imagin- 
ation to  see  that  the  problems  of  the  roll  designer  for  merchant  mills  are 
many  and  the  most  difficult  to  solve.  That  the  art  of  designing  rolls  for 
these  small  mills  must  have  made  wonderful  progress  is  indicated  by  the 
recent  appearance  of  sections  of  the  most  intricate  design,  yet  rolled  with 
minute  accuracy.  But  the  designing  of  passes  for  the  sections  is  but  one 
of  the  problems  confronting  the  roll  designer,  as  a  visit  to  the  mills  will 
show.  Among  these  should  be  mentioned  the  great  number  of  designs, 
which  require  the  most  systematic  filing  and  recording  of  rolls,  templets, 
and  tools.  The  ingenuity  of  the  roll  designer  is  taxed  to  the  utmost  to 
keep  the  number  of  rolls  at  a  minimum.  So,  the  visitor  in  the  mills  will 
find  that  numerous  sizes,  differing  by  only  a  few  thousandths  of  an  inch, 
are  placed  in  the  same  roll.  The  efforts  of  the  roll  designer  along  this 
line  are  especially  noticeable  in  the  roughing  stands.  Here  the  process  is 
merely  one  of  reduction,  the  piece  leaving  the  roughers  in  the  form  of  a 
square  or  rectangle.  To  bring  about  this  reduction  one  of  five  methods, 
or  combination  of  passes,  may  be  employed.  Thus,  in  continuous  roughing, 
the  student  will  observe  four  methods  in  use,  which  may  be  designated  as: 
1.  Diamond — square;  2.  Oval — square;  3.  Flat-and-edging;  4.  All- 
diamond-to-square.  In  three-high  roughers,  either  the  flat-and-edging  or 
the  diamond-pass  method  is  used.  The  following  sketch  is  intended  to 
illustrate  these  methods.  Nearly  all  the  shaping,  except  in  the  case  of 
deformed  bars  already  alluded  to,  is  done  in  the  stands,  called  the  strands, 
immediately  following  the  rougher.  The  strands  are  sometimes  preceded 
by  an  auxiliary  set  of  roughers  called  the  pony  roughers.  The  planisher 
may  be  employed  as  a  last  forming  pass  only  or,  in  addition,  to  give  a  finish 
to  the  bar.  The  finishing  pass  is  reserved  exclusively  for  removing  the 
little  irregularities  of  the  previous  rolling. 

Economic  Features  of  Roll  Designing:  It  scarcely  needs  to  be 
pointed  out  that  aside  from  the  successful  rolling  of  the  various  sections, 
the  chief  incentive  behind  the  efforts  of  the  merchant  mill  roll  designer 


MERCHANT  MILL  ROLL  DESIGN 


484  THE  ROLLING  OF  STEEL 


is  found  in  the  necessity  for  economy. 
The  rolls,  alone,  as  maybe  surmised  from 
what  has  been  said  concerning  their 
manufacture,  etc.,  are  very  expensive, 
and  a  large  number  of  rolls  on  hand 
means  a  large  investment  in  something 
that  is  idle  most  of  the  time.  Added 
to  this  feature  is  the  expense  of  roll 
changes,  during  the  time  for  which  the 
entire  mill  is  closed  down.  In  the  elimi-  ^_ 
nation  of  roll  changes  much  depends  on  ^y  c2 
the  way  the  orders  are  scheduled.  This 
point  should,  therefore,  always  be  con- 
sidered in  making  up  the  mill  schedules, 
and  is  a  problem  to  be  solved  in  making 
up  promises  of  delivery  for  small  lots. 
As  an  example  of  how  scheduling  is 
done,  the  system  employed  at  the  Upper 
and  Lower  Union  Mills  at  Youngstown 
is  explained. 

Making  Up  Schedules — The  Order 
in  the  Office:  Upon  receipt  of  the  large 
buyers'  schedule,  which  usually  comes 
about  the  middle  of  the  month  for  the 
following  month,  the  respective  schedule 
clerks  pick  out  from  the  files  the  index 
cards  corresponding  to  the  buyers' 
schedule  and  file  them  in  a  desk  file.  At 
the  same  time  all  those  index  cards  with 
promises  on  them  for  the  next  month  are 
taken  out  and  put  along  with  those 
already  in  the  desk  file.  In  addition  to 
these  the  oldest  index  cards  are  also 
worked  in  whenever  it  is  possible .  Before 
these  index  cards  are  put  in  the  desk 
file,  however,  they  are  checked  against 
the  book  orders  for  mistakes,  etc.,  and 
the  date  of  order.  By  this  means  it  is 
known  that  the  item  is  either  in  the 
desk  file  or  out  on  the  mill.  The 
index  cards  in  the  desk  files  thus  represent 
all  the  promised  and  scheduled  material 
for  the  next  month.  From  these  files 
the  schedule  clerks  make  up  rollings 
for  their  respective  mills.  For  this 


MERCHANT  MILL  PRODUCTS 


485 


joii  oj,  — 


486  THE  ROLLING  OF  STEEL 

purpose  index  cards  showing  the  different  sizes  of  sections  and  grades 
of  steel  on  the  schedule  are  also  kept.  To  keep  the  scrap  loss 
on  the  mill  to  a  minimum  the  longest  exact  cuts  are  put  first,  the  exact  short 
lengths  come  next  and  after  these  are  placed  the  common  lengths.  There- 
fore, when  shearing  the  long  exact  cuts,  the  short  ends  may  be  sheared  into 
the  shorter  lengths; and  if  a  long  piece  comes  at  the  end,  it  maybe  sheared 
to  one  of  the  long  common  length  cuts.  The  amount  of  tonnage  to  a  roll- 
ing varies  with  the  mill  and  the  section  being  rolled.  In  making  up  a 
rolling  it  must  be  watched  that  a  car  load  of  material  is  checked  out,  so 
material  will  not  have  to  be  piled.  If  there  is  not  enough  material  at 
either  Upper  or  Lower  Mills  to  make  up  a  car  load  for  the  customer  the 
products  for  both  Upper  and  Lower  for  that  customer  are  combined  to 
make  up  a  car  load,  the  shipping  offices  having  previously  decided  at 
which  plant  to  start  the  car.  Sometimes  an  order  will  be  transferred  from 
one  mill  to  the  other  so  as  to  prevent  this  condition.  In  this  case,  the 
order  is  transferred  by  making  out  two  correction  slips.  One  of  the  slips 
goes  to  the  one  mill  telling  its  foreman  to  cancel  the  order  that  is  to  be 
transferred,  and  the  other  goes  to  the  other  mill  telling  its  foreman  to 
reinstate  the  order  mentioned.  The  correction  slips  are  made  out  in 
triplicate  form,  a  copy  of  each  remaining  at  the  order  department,  and  the 
original  and  a  copy  of  each  going  to  the  proper  shipping  office  where  the 
original  is  returned  and  noted  to  the  order  department,  while  the  copy  is 
kept  on  file  at  the  shipping  office.  The  schedule  clerk  in  the  order  depart- 
ment keeps  a  record  of  the  orders  he  sends  to  the  mill  order  clerk  for  each 
mill  and  from  time  to  time  checks  up  with  him  regarding  the  amount  of  steel 
on  hand.  After  a  rolling  has  been  made  up,  the  index  cards  are  hectograph- 
ed  and  three  copies  are  made.  These  copies  are  known  as  mill  order  sheets. 

The  Order  at  the  Mill— Size  of  Billet  or  Bloom :  The  original  index 
cards,  together  with  the  copies,  are  sent  to  the  mill  order  clerk,  who  gives 
the  index  cards  to  the  shipping  office,  keeps  one  copy  of  the  mill  order, 
and  sends  the  other  two  to  the  mill  foreman.  These  should  be  sent  over 
to  the  mills  at  least  twelve  hours  before  they  are  to  be  put  out  on  the  mill, 
so  that  the  foreman  will  have  time  to  figure  out  the  weight  billet  required 
and  to  order  the  steel  from  the  mill  stocker.  Due  to  various  influences, 
however,  the  orders  are  often  sent  out  only  a  few  minutes  before  they  are 
put  on  the  milL  In  figuring  out  the  billet  or  bloom  required  for  the  order, 
the  foreman  figures  the  length  to  which  he  can  run  the  material  on  the 
cooling  bed  and  obtain  multiple  lengths  of  the  cut  ordered,  taking  into 
consideration  both  the  length  of  the  hot  bed  and  the  mill  practice.  He 
then  multiplies  the  mill  length  that  the  bar  is  to  be  rolled  on  by  the  weight 
per  foot  of  the  section,  which  gives  him  the  weight  billet  or  bloom  needed, 
not  allowing  for  scrap  or  furnace  loss.  About  10%  is  added  to  most  orders 
to  offset  furnace  and  scrap  loss.  However,  this  factor  changes  with  the 
section  and  the  cut.  Common  length  cuts  on  large  material  requires  some- 
times as  little  as  5%,  but  on  the  other  hand  light  material,  such  as  crescents, 


MERCHANT  MILL  PRACTICE  487 


on  which  the  cut  is  exact  and  the  inspection  rigid,  the  amount  added  will 
sometimes  be  as  high  as  25%.  In  figuring  the  weight  billet  required,  the 
width  of  the  furnace  must  also  be  taken  into  account.  Blooms  for  common 
grades  of  steel  are  furnished  by  the  Ohio  Works  in  different  weights, 
increasing  by  fives  from  one  hundred  to  three  hundred  pounds,  while  bil- 
lets, unless  otherwise  requisitioned,  are  furnished  in  lengths  of  thirty  feet. 
After  figuring  the  orders,  the  mill  foreman  makes  out  a  steel  order  with 
two  carbon  copies.  The  original  is  kept  on  file;  one  of  the  copies  is  given 
to  the  stocker,  who  sees  that  the  billets  or  blooms  are  cut  to  weight  and 
delivered  to  the  heating  furnaces;  and  the  other  is  given  to  the  steel  yard 
foreman,  so  he  can  check  the  same  against  his  records.  The  orders  are 
then  given  to  the  shear  foreman  and  the  roller,  the  size  of  the  section 
being  marked  on  the  margin  of  the  iatter's  sheet  in  large  clear  figures  in 
order  to  eliminate  any  possible  error  in  size.  When  the  shipping  office 
receives  the  index  card  from  the  mill  order  clerk,  the  card  is  blue- 
penciled  showing  date  the  order  was  received  from  the  order  department. 
It  is  then  returned  to  the  mill  order  clerk  who  files  it  until  he  places  the 
order  on  the  mill.  The  card  is  again  given  to  the  shipping  office  when  the 
order  is  placed  on  the  mill,  and,  this  time,  the  date  the  order  is  put  on  the 
mill  is  marked  with  black  pencil.  A  shipping  clerk  looks  up  the  book 
order  and  marks  the  index  card  with  the  information  as  to  whether  the 
material  is  to  be  piled  or  loaded  into  a  railroad  car,  which  is  dependent 
upon  how  much  material  for  that  customer  is  being  rolled.  The  marked 
index  card  is  then  filed  according  to  size  and  section. 

SECTION   IV. 

ROLLING   PRACTICE  IN   MERCHANT   MILLS. 

The  Roller :  While  the  roll  designer  is  indispensible,  and  the  roll  shop 
represents  the  heart  of  the  rolling  mill  plant,  much  depends  on  the  roller. 
He  must  be  a  man  with  not  a  little  ability,  capable  of  exercising  good  judg- 
ment at  all  times  and  possessing  considerable  practical  knowledge.  With 
closer  and  closer  rolling  tolerances  being  demanded  by  the  customer  and 
larger  tonnages  required,  due  to  the  rapid  growth  of  the  steel  industry, 
the  roller  has  been  placed  in  the  difficult  position  of  meeting  rigid  speci- 
fications and  breaking  tonnage  records  at  the  same  time.  This  achieve- 
ment appears  the  more  remarkable  when  it  is  recalled  that  all  the  training 
the  roller  gets  is  along  practical  lines.  His  only  school  is  the  school  of 
experience  in  which  a  man  is  never  graduated.  It  is  manifestly  impossible, 
therefore,  to  explain  satisfactorily  the  knowledge  of  the  roller  or  the  method 
of  his  working.  The  best  that  can  be  done  is  to  point  out  some  of  the 
duties  of  the  roller  and  mention  a  few  of  the  precautions  he  must 
observe. 

Precautions  in  Rolling:  In  a  word,  it  is  the  duty  of  the  roller  to  see 
that  the  rolling  is  .properly  done  and  the  material  meets  the  specification 


488  THE  ROLLING  OF  STEEL 


as  to  size,  shape  and  freedom  from  rolling  defects.  In  building  up  rolls 
in  the  housings  care  should  be  taken  by  the  roller  that  they  are  plumb, 
square  and  level.  If  the  rolls  are  not  plumb,  i.  e.,  if  the  line  joining  their 
centers  is  not  straight  and  perpendicular  to  a  horizontal,  the  bar  will  not 
deliver  properly,  and  trouble  with  the  guides  will  undoubtedly  occur.  This 
condition  is  often  caused  by  bearings  wearing  out  or  poor  babbitting 
originally  and  can  only  be  remedied  by  changing  bearings  or,  in  some 
instances,  by  the  use  of  side  liners  or  wedges.  Should  the  rolls  be  out  of 
square,  that  is,  if  the  center  of  the  pass  in  the  top  roll  is  not  directly  above 
the  center  of  the  pass  in  the  lower  roll,  the  bar  will  be  out  of  square  and 
will  twist  as  it  issues  from  the  rolls.  In  order  to  square  up  the  rolls,  set 
screws  which  work  against  the  bearings  are  provided  on  the  sides  of  the 
housings,  and  thus  the  rolls  can  be  thrown  either  one  way  or  the  other  as 
the  case  may  demand.  The  directions  for  correcting  this  fault  are,  in  the 
language  of  the  mill,  "Follow  the  twist,"  and  the  top  roll  is  always  thrown 
over  in  the  direction  that  the  bar  is  twisting.  In  the  event  that  the  rolls 
are  not  level,  that  is,  perfectly  parallel,  more  work  will  be  done  on  one  side 
than  on  the  other,  with  the  result  that  the  bar  will  not  deliver  straight 
but  will  tend  to  curve  around  toward  the  side  on  which  there  is  the  lightest 
draft,  due  to  the  other  side  being  elongated  the  more.  This  condition  may 
be  remedied  either  by  the  use  of  liners  or  by  operating  the  screw  down  at 
the  proper  side.  Guides  and  guards  play  a  most  important  part  in  rolling 
mill  practice,  and  the  proper  setting  of  these  is  one  of  the  roller's  most 
important  duties.  His  assistants  may  set  the  guides  for  the  strand  and 
planishing  rolls,  but  those  for  the  finishing  pass  are  always  set  by  the 
roller.  Entering  guides  on  the  finishing  passes  are  usually  closed,  the 
inner  end  being  so  shaped  that  it  will  provide  sufficient  bearing  to  hold  the 
piece  up  in  correct  position  while  entering  the  pass.  If  the  guides  are  not 
set  properly,  the  bar  will  not  be  formed  rightly.  Especially  when  rolling 
rounds,  the  entering  guides  should  be  tight  in  order  to  hold  the  oval  in  a 
vertical  position,  for  a  leaning  to  either  one  side  or  the  other  will  produce 
a  high  and  a  low  shoulder  on  the  finished  round.  The  position  of  the 
guides  on  the  delivery  side  is  also  most  important,  for  since  the  bar  has  a 
tendency  to  follow  the  smaller  roll  diameter,  the  guide  against  which  the 
bar  is  thrown  must  be  watched  most  carefully.  If  the  bottom  roll  is  the 
smaller,  then  the  bottom  guide  should  not  be  placed  too  low,  for  the  bar 
coming  out  would  have  a  tendency  to  follow  the  roll  down  for  a  short  space 
before  striking  the  guide.  This  would  cause  an  up  and  down  kink,  or  a 
buckle.  A  short  guide  has  the  same  effect. 

Rolling  Defects:  In  addition  to  working  for  the  proper  size  and  finish 
on  the  bar,  the  roller  must  watch  for  such  surface  defects  as  overfills  or 
pinches,  underfills,  buckles,  slivers,  seams,  laps,  firecracks,  roll  marks,  etc. 
Overfills  or  pinches  must  be  watched  especially  in  changing  from  Bessemer  to 
open  hearth  steel,  as  the  latter  has  more  of  a  tendency  to  spread  than  does 
the  former.  When  overfills  occur,  the  amount  of  stock  entering  the  pass 


MERCHANT  MILL  PRACTICE  489 


that  is  producing  the  overfill  must  be  reduced  by  adjusting  the  rolls  in 
preceding  passes.  Underfills  are  corrected  by  reversing  these  operations. 
Buckles  are  sometimes  caused  by  worn  out  pinions.  Slivers  can  be 
produced  from  many  causes  at  the  blooming  mill  or  by  the  bar  shearing 
against  a  guide  or  collar  of  a  roll  at  the  finishing  mills.  The  former 
condition  cannot  be  corrected  by  the  merchant  mill  roller,  but  the  latter 
can  be  eliminated  by  a  proper  adjustment  of  the  proper  guide  or  by  reducing 
the  stock  in  the  bar  which  is  shearing  against  the  collar.  Seams  are  defects 
in  the  steel  that  cannot  always  be  corrected  by  the  finishing  mill,  as  they 
are  usually  formed  in  the  bloom  or  the  billet.  A  lap  is  caused  by  an  overfill 
or  fin  being  formed  and  then  being  doubled  over  and  rolled  down  in  the 
subsequent  passes.  This  defect  can  be  controlled  by  the  roller  by  going 
back  to  the  stand  at  which  the  overfill  was  formed  and  reducing  the  stock. 
Firecracks  are  caused  by  the  rolls  becoming  overheated  and  cracking  on 
the  surface.  These  cracks  cause  corresponding  small  elevations  on  the 
surface  of  the  bar,  which  in  some  instances  condemn  the  material.  When 
this  defect  appears,  the  roller  "moves  over"  and  uses  a  "clean"  pass.  The 
same  procedure  is  followed  when  any  other  roll  mark  appears  on  the  finished 
bar.  Roll  marks  occur  at  equal  intervals  along  the  bar  and  signify  that 
there  is  a  piece  out  of  the  roll  or  that  the  roll  is  marking  the  bar  with  each 
revolution  in  some  other  manner. 

Two  Different  Finishes  on  bars  are  furnished  at  the  Youngstown 
plant,  namely,  common  and  special.  The  special  finish  has  a  smooth,  highly 
polished  appearance  and  is  produced  by  cleaning  all  scale  from  the  bar  at 
the  planishing  stand  and  finishing  at  such  a  low  temperature  that  no  more 
scale  will  form  on  the  surface. 

The  Special  Finish  is  produced  on  rounds  by  holding  the  square  back 
before  entering  the  planishing,  until  a  dark  scale  has  formed  and  then  bend- 
ing the  bar  with  a  pair  of  special  tongs  as  it  enters  the  rolls.  A  stream  of 
water  plays  directly  upon  the  bar  as  it  enters  both  the  planishing  and  finish- 
ing passes,  and  scouring  blocks  covered  with  emery  powder  are  used  on  the 
finishing  stand  in  order  to  keep  the  pass  clean.  Material  requiring  the 
special  finish  is  always  rolled  ahead  of  the  common  orders  of  like  sizes, 
so  that  a  clean  pass  will  be  available.  Flats  are  not  scraped  in  order  to 
furnish  the  special  finish,  but  are  simply  held  back  until  their  temperature 
reaches  the  critical  range  before  entering  the  planishing  pass.  On  large 
fiats,  water  is  used  on  the  bar  as  it  issues  from  the  planishing,  so  that  the 
scale  thus  broken  up  will  be  removed  and  not  be  rolled  into  the  steel. 
Another  reason  for  using  water  on  large  sections  is  that  they  will  be  delivered 
to  the  hot  beds  below  the  scale  forming  temperatures.  Cooling  is  un- 
necessary, however,  on  small  sections,  such  as  crescents,  half  ovals  and 
ovals,  as  these  lose  their  heat  so  rapidly  that  even  water  is  not  used  directly 
on  the  bar.  A  scraper,  located  at  the  entering  side  of  the  finishing  stand, 


490  THE  ROLLING  OF  STEEL 

is  the  only  means  used  for  producing  the  special  finish  upon  these  sections. 
Due  to  the  fact  that  scale  adheres  more  tenaciously  to  open  hearth  than 
it  does  to  Bessemer  steel,  the  latter  takes  a  much  better  finish  than  the 
former.  Open  hearth  steel  will  become  smooth  but  does  not  have  the 
highly  polished  appearance  of  Bessemer  steel.  It  is  the  roller's  experience 
that  Bessemer  screw  steel  takes  the  best  finish  of  any  grade  turned  out  at 
the  converting  mills.  This  grade  not  only  takes  a  smooth  finish  but  some 
times  gives  a  mirror-like  surface.  It  should  be  observed  that  the  holding 
back  of  the  bar  to  produce  this  finish  may  so  retard  the  rolling  as  to 
decrease  seriously  the  total  output  of  the  mill. 


SECTION   V. 

SHEARING   AND    BUNDLING   MERCHANT   MILL   PRODUCTS. 

The  Methods  of  Shearing  and  Bundling  vary  at  the  different  plants 
according  to  equipment,  product,  location,  etc.,  and  no  description  of  value 
yet  general  enough  to  be  descriptive  of  all  plants  can  be  given.  As  the 
greatest  variety  of  sections  are  produced  at  the  Youngstown  Upper  and 
Lower  Union  Works,  a  brief  outline  of  the  methods  and  practices  at  this 
plant  may  be  found  of  value. 

Duties  of  the  Shear  Foreman:  The  man  who  is  responsible  for 
completing  orders,  i.  e.,  for  the  shearing  and  the  bundling  on  each  mill, 
is  the  shear  foreman.  His  force  is  usually  composed  of  a  shearman,  a 
gauger,  a  push-up,  a  pull-up,  and  two  or  more  bundlers.  The  first  duty 
of  the  shear  foreman  is  to  keep  the  different  orders,  heats  and  turns  separate 
on  the  cooling  beds  and  to  tag  each  item  on  the  truck  properly.  The 
different  lots  are  kept  separate  on  the  trucks  by  means  of  bands.  A  load 
sheet  is  made  out  for  each  truck,  showing  the  material  loaded  on  it.  When 
the  truck  is  full,  it  is  the  duty  of  the  shear  foreman  to  notify  the  yard  master 
or  dinkey  engineer  to  pull  the  load  to  the  warehouse,  or  shipping  room. 
It  is  also  the  duty  of  the  shear  foreman  to  set  the  gauge  for  shearing  the 
material,  allowing  a  certain  amount  for  contraction  during  the  cooling 
process.  The  amount  allowed  on  the  smaller  mills  is  one-fourth  inch  over 
or  under  for  every  five  feet,  but  this  amount  varies  with  the  size  of  the  bar. 
When  material  is  to  be  bundled,  the  weight  of  the  bundles  is  nearly  always 
specified,  but  when  instructions  are  not  given,  it  is  the  mill  practice  to 
bundle  material  to  weigh  100  to  150  pounds  per  bundle.  By  multiplying 
the  weight  per  foot  of  the  section  by  the  cut  and  dividing  the  product  into 
the  weight  of  a  bundle,  the  shear  foreman  determines  how  many  bars  to 
put  in  a  bundle;  but  in  order  to  check  himself  up  he  weighs  the  first  bundle 


MERCHANT  MILL  PRACTICE  491 

of  each  new  cut.  It  is  the  object  of  the  shear  foreman  to  put  the  same 
number  of  bars  in  each  bundle,  as  this  not  only  makes  all  the  bundles  of 
uniform  weight  but  facilitates  the  recounting  of  a  bar  order  by  the  men  in 
the  warehouse.  On  some  mills  the  head  bundler  counts  the  bars,  while  on 
other  mills  tally  boys  are  employed.  In  bundling  material  up  to  twelve 
feet  on  domestic  orders  only  two  "Carnegie"  bands  are  used.  Up  to  twenty 
feet  three  "Carnegie"  bands  are  used,  while  four  are  used  on  all  cuts  twenty 
feet  and  over. 

Bundling  Export  Material :  On  export  orders,  the  weight  of  a  bundle  is 
always  specified,  the  weight  usually  being  112  pounds,  so  that  twenty  bundles 
make  one  gross  ton.  On  lengths  up  to  fourteen  feet  three  bands,  marked 
"Carnegie,  Made  in  U.  S.  A.,"  are  used.  From  fourteen  feet  to  twenty-two 
feet  four  bands  are  used,  and  one  additional  is  put  on  for  every  six  feet  above 
twenty-two  feet.  On  all  export  orders,  special  "export"  tongs  are  used, 
as  with  these  tongs  the  material  can  be  tied  very  securely.  The  following 
rules  apply  to  the  handling  of  export  orders:  All  orders  must  be  complete. 
All  bundles,  excepting  the  last,  must  contain  the  same  number  of  bars. 
All  bundles  are  to  be  tightly  tied  with  "export"  tongs  whenever  possible, 
and  bands  used  are  to  be  in  accordance  with  instructions  on  orders.  These 
instructions  may  call  for  export  bands,  plain  bands,  or  wire.  All  export 
material  must  be  loaded  on  separate  trucks,  except  in  very  small  orders, 
or  when  the  material  is  needed  by  the  warehouse  to  complete  an  order 
hurriedly.  All  trucks  containing  any  export  material  must  bear  a  red  export 
tag,  and  all  excesses  are  to  be  loaded  on  trucks  but  kept  distinctly  separate, 
tagged  plainly  as  "Excess,"  and  showing  order  number,  customer,  size, 
etc.  The  name  of  the  man  who  is  responsible  for  tallying  and  bundling 
is  placed  on  the  tag,  and  all  orders  are  very  plainly  tagged,  the  tags  being 
so  placed  that  there  is  little  liability  of  their  being  torn,  pulled  off  or  made 
illegible.  On  all  trucks  are  placed  load  sheets  which  are  put  in  oiled 
envelopes  so  that  weather  conditions  can  not  destroy,  or  blur,  the  writing. 

Special  Bundling:  Some  material,  such  as  ovals,  tees,  etc.,  often 
specify  "Tie  with  wire,"  while  other  orders,  especially  for  large  material, 
specify  the  material  to  be  shipped  loose.  A  good  many  orders,  such  as 
hoops,  flats,  rounds,  squares,  and  small  nut  steel,  are  often  ordered  coiled. 
This  is  accomplished  by  means  of  coilers  with  adjustable  pins  so  that  coils 
of  different  diameters  can  be  furnished.  The  usual  diameter,  however,  is 
twenty-four  inches.  These  coilers  are  located  at  one  end  of  the  hot  bed 
or  at  some  other  convenient  point  according  to  available  space.  All  coilers 
are  electrically  driven. 

Handling  the  Material  in  the  Warehouse:  When  the  truck  load  of 
material  arrives  at  the  warehouse,  the  pile-boy  takes  the  load  sheet  into 
the  office  and  gets  the  corresponding  index  cards,  because  the  load  sheet 
shows  only  the  order  number,  size,  cut,  grade  of  steel  and  remarks.  The 
index  cards  show  customers  name  and  loading  and  shipping  instructions. 


492  THE  ROLLING  OF  STEEL 

As  each  item  is  weighed  off  from  the  truck,  it  is  entered  on  a  weight  sheet 
by  a  weigh-man  and  checked  off  on  both  the  index  card  and  load  sheet. 
If  the  index  card  is  marked  "Car"  a  car  is  started  for  that  customer,  if 
this  has  not  already  been  done,  and  material  is  so  loaded.  If  index  card 
is  marked  'Tile"  the  item  is  piled  and  so  noted  on  the  weight  sheet.  One 
weight  sheet  is  made  out  for  each  truck  load,  and  when  this  car  has  been 
weighed  off,  the  sheet  is  checked  off  on  the  car  card,  of  which  there  is  one 
for  each  car,  and  returned  to  the  office.  Here  the  weight  sheets  are  checked 
against  the  order  books.  Memorandums  are  made  out  for  the  items  that 
have  been  piled  so  that  these  can  be  given  out  to  the  weighmen  when  a 
car  load  has  been  started  for  the  customer.  When  an  item  of  an  order  is 
under  weight  or  short  in  number  of  pieces,  the  shortage  is  discovered  by 
a  weekly  survey  of  the  order  books  by  a  clerk  in  the  shipping  office,  who 
makes  out  a  reindex  card  for  the  shortage  and  notes  the  date  made  out 
with  blue  pencil  on  both  the  reindex  card  and  the  book  order.  If,  however, 
there  is  a  chance  to  get  the  item  on  the  mill  immediately,  the  book  order 
and  the  index  card  are  black  penciled.  A  rolling  order  is  made  out  from 
the  reindex  card  and  hectographed,  after  which  the  index  card  and  three 
mill  order  sheets  are  given  to  the  mill  order  clerk.  He  returns  the  reindex 
card  to  the  shipping  offices,  and  if  he  does  not  have  the  grade  of  steel  in 
stock,  he  has  to  make  out  a  requisition  for  it,  the  procedure  then  being 
the  same  as  for  ordinary  orders. 

Straightening:  At  the  lower  mill,  straightening  is  done  by  the  Labor 
Department,  machines  for  this  purpose  being  located  at  three  different 
places.  These  machines  are  of  the  seven  roll  type,  the  rolls  being  built 
up  in  a  casting  similar  to  roll  housings.  Four  rolls  are  below  and  three 
above,  the  bar  passing  between  in  grooves  which  are  designed  to  fit  each 
separate  section.  On  account  of  the  vast  amount  of  tire  and  window  sash 
sections  rolled  at  the  Upper  Mills,  the  straightening  is  under  the  juris- 
diction of  a  special  department  for  that  purpose.  Angles  and  sash  sections, 
molding  tees,  and  mud  guard  sections  are  straightened  at  the  mill,  there 
being  a  straightening  machine  located  at  each  mill  where  such  material 
is  rolled.  Round  edge  tire,  however,  is  straightened  in  the  tire  house, 
where  two  straightening  machines  of  a  new  type  are  located.  These  are 
more  flexible  than  the  old  type  and  are  more  easily  adjusted  to  the  various 
sizes. 

Invoicing:  After  the  cars  have  been  loaded,  the  car  cards  are  taken 
into  the  shipping  office,  and  from  these,  invoices  are  made  out.  The  original 
office  copy  of  the  invoice,  which  is  made  out  in  the  shipping  office,  is  sent 
to  the  order  department  where  it  is  carefully  checked  against  the  book 
order,  the  number  of  bars  or  bundles  and  tonnage  being  entered  on  same. 
The  invoices  are  next  given  to  a  clerk  who  enters  all  detailed  information 
on  a  "recap"  sheet.  The  credits  for  the  various  sections  and  sizes  are  also 
entered  under  the  proper  headings  on  a  "credit  recap  sheet." 


MERCHANT  MILL  PRACTICE  493 

SECTION   VI. 

INSPECTION   DEPARTMENT  OF  A   MERCHANT  MILL  PLANT. 

The  Inspection  Department  makes  all  physical  tests  and  keeps 
records  and  samples  of  the  various  sections.  One  of  the  duties  of  this 
department  is  to  inspect  and  accept  or  reject  all  special  steel  before  being 
rolled  into  finished  product.  Check  analysis  is  made  of  all  steel  requiring 
the  same,  and  a  close  inspection  of  all  material  when  being  rolled  is  provided 
for.  All  special  steel  ordered  from  the  semi-finishing  mills  must  pass 
inspection  by  this  department.  Approval  or  disapproval  of  material  is 
based  upon  chemical  analysis  and  surface  conditions.  Only  very  low 
limits  for  the  various  impurities  are  allowed  on  special  steels,  and  the 
inspection  is  very  rigid.  Consequently,  any  heats  not  falling  within  the 
requirements  must  receive  special  attention.  Much  in  the  way  of  good 
judgment  is  required  to  dispose  of  such  heats  satisfactorily.  Usually,  the 
department  will  endeavor  to  consult  the  customer  before  permitting  an  off 
grade  heat  to  be  rolled  as  originally  planned.  Certain  orders  require  the 
ladle  analysis  to  be  checked  before  being  rolled  into  the  finished  bar.  Orders 
requesting  check  analysis  are  held  in  the  yard  until  drillings  from 
the  billets  are  analyzed.  If  this  analysis  shows  that  the  composition  of 
the  steel  is  as  ordered,  the  steel  is  rolled  on  the  order  for  which  it  was 
originally  intended.  If  the  check  analysis  does  not  practically  agree  with 
the  ladle  analysis,  the  steel  is  applied  on  a  less  particular  order.  Check 
analysis  may  also  be  made  on  finished  material.  Some  orders  require  that 
the  steel  be  inspected  for  surface  defects  before  rolling.  In  such  cases 
each  billet  is  carefully  examined  to  detect  any  slivers,  seams,  checks,  or 
faulty  shearing  that  may  occur.  Billets  found  to  be  defective  are  chipped 
and  put  into  condition  for  rolling  if  at  all  possible.  When  orders  specify 
physical  requirements,  it  is  then  the  duty  of  this  department  to  supply  such 
chemical  specifications  as  will'  fulfill  the  physical  requirements. 

Another  Function  of  this  Department  is  that  of  mill  inspection, 
which  is  one  of  most  importance.  In  this  capacity  the  department  acts 
as  a  check  upon  the  rolling.  Mill  inspection  requires  one  man  on  each  mill, 
devoting  his  entire  time  to  gauging  and  watching  for  faulty  steel.  Sections 
not  fulfilling  the  prescribed  measurements  are  either  held  for  further 
inspection  or  thrown  out  as  scrap.  The  rollers  as  well  as  the  inspectors, 
have  the  given  dimensions  and  tolerances.  The  inspectors  check  the  rollers 
and  inform  them  of  any  faults  that  the  rollers  themselves  have  not  already 
detected.  In  case  an  inspector  does  not  accept  steel  as  rolled,  and  the 
roller  continues  to  make  the  section,  the  inspector  signals  for  the  depart- 
ment superintendent  and  lays  the  case  before  him.  If  the  fault  cannot  be 
remedied,  and  it  is  known  the  customer  will  not  accept  the  steel  as  rolled, 
the  mill  must  go  off  the  order.  The  defects  watched  for  most  closely 
depend  upon  the  section  being  rolled.  Accurate  size  applies  to  all  sections. 


494  MERCHANT  MILL  PRODUCTS 

For  the  more  complicated  sections  templets  are  furnished.  Usually  one 
exact  and  one  full  templet  is  made.  For  gauging  rounds,  squares,  flats, 
etc.,  only  a  gauge  and  micrometer  is  used.  Readings  on  the  micrometer 
are  accurate  to  .001  inch,  while  on  the  gauge  one-sixty-fourth  inch  is  about 
the  most  exact  reading  that  can  be  determined.  Other  tools  used  for  special 
purposes  are  squares  and  steel  tapes.  The  square  is  used  to  detect  diamond- 
ing in  certain  instances  where  each  surface  must  be  at  right  angles  to  the 
adjacent  one.  The  tape  is  used  when  inspecting  clip  sections,  to  determine 
the  regularity  of  the  impressions  that  are  rolled  on  the  bar. 

Surface  Defects:  The  inspector  is  responsible  for  the  detection  of 
surface  defects.  These  may  appear  as  buckles,  kinks,  overfills,  underfills, 
slivers,  laps,  seams,  or  burned  steel.  While  the  nature  and  causes  of  these 
defects  have  already  been  more  or  less  fully  explained,  the  following  resume" 
of  defects  most  likely  to  occur  in  merchant  mill  rolling  is  appended  for 
ready  reference: 

Buckles  and  Kinks:  A  bar,  when  delivered  from  the  finishing  rolls, 
may  be  wavy,  either  up  and  down  or  sideways.  The  former  is  known  as 
a  buckle,  while  the  latter  is  a  kink.  These  defects  are  more  injurious  to 
some  sections  than  others.  However,  all  sections  should  be  rolled  as  free 
from  buckles  and  kinks  as  possible.  Crescents  have  a  tendency  to  buckle, 
consequently  they  must  be  watched  closely. 

Fins:  If  a  bar  has  a  fin  or  extra  amount  of  metal  at  the  sides  where 
the  finishing  rolls  come  together,  the  bar  is  said  to  be  over-filled.  Bars 
rolled  for  cold  drawing  must  be  free  from  over-fills,  for  these  draw  into 
laps.  On  the  other  hand,  in  order  to  get  perfect  corners  on  half  ovals,  a 
well  known  file  manufacturer  requests  a  small  overfill  at  the  edges. 

Underfills:  When  a  bar  is  scant  in  certain  dimensions  or  when  it  is 
not  completely  filled  oiit,  the  bar  is  said  to  be  underfilled.  This  defect 
sometimes  appears  on  rounds  and  channels. 

Slivers  are  loose  pieces  of  steel  rolled  flat  on  a  bar.  They  may  be 
present  on  the  billet  or  be  caused  by  faulty  shearing,  or  incorrect  entering 
of  the  bar  in  a  closed  pass.  Slivered  steel  is  thrown  out  as  scrap  and  seldom 
held  for  further  inspection. 

Laps:  If  a  bar  is  given  a  pass  in  the  rolls  after  an  overfill  has  been 
produced,  a  lap  usually  results.  This  defect  is  especially  liable  to  occur 
with  skelp,  hoop  and  cotton-tie.  Faulty  ingots  and  poor  rolling  at  the 
semi-finishing  mills  also  cause  laps. 

Seams:  Steel  must  be  inspected  carefully  for  seams,  a  surface  defect 
always  difficult  to  detect.  A  seam  is  a  crevice  in  steel  that  is  closed 
up  but  not  welded.  Seams  are  caused  by  blow  holes  and  cracks  in  the 
ingot,  as  well  as  faulty  methods  of  rolling.  They  render  steel  unfit  for 
hardening. 


INSPECTION  495 


Burned  Steel  shows  up  in  the  finished  bar  in  the  form  of  rough,  checked 
edges.  Burned  steel  is  ruined,  and  the  only  alternative  is  to  scrap  it. 

Roll  Marks:  Sometimes  a  roll  is  nicked,  or  a  piece  breaks  off  the 
roll,  resulting  in  periodic  impressions  along  the  bar.  The  defect  is 
corrected  only  by  a  new  pass.  Fire  cracked  rolls  make  similar  impressions. 

Finish:  The  finishing  pass,  if  worn,  does  not  give  a  smooth  surface, 
consequently  when  the  surface  of  a  bar  is  not  up  to  the  standard  in  finish 
the  pass  must  be  changed.  This  defect  is  especially  objectionable  when 
rolling  cotton  tie,  hoop,  skelp  and  sections  requiring  the  special  finish. 

Pipe:  The  inspector  must  watch  the  sheared  ends  of  bars  for  piping. 
This  defect,  however,  is  usually  detected  at  the  billet  shears  before  the 
steel  is  charged. 

Testing  for  Defects:  Tests  for  detecting  some  of  these  defects  are 
employed  by  the  inspectors.  The  tests  most  commonly  employed  for  this 
purpose  are  the  upset,  forging  and  pickle  tests.  The  upset  test  consists  of 
heating  a  short  sample  piece  in  a  forge  or  furnace  and  upsetting  under  a 
hammer.  This  is  a  severe  test  and  readily  shows  up  seams  and  laps.  For 
forging  tests,  a  bar  about  ten  inches  long  is  heated  and  forged  along  the 
longitudinal  axis  of  the  bar,  which  is  then  nicked  and  broken.  Piped  steel 
is  readily  detected  by  this  treatment,  as  the  forging  opens  up  the  pipe. 
The  upset  test  is  more  often  used  than  the  forging  test,  especially  when 
rolling  forging  steel.  The  pickle  test  consists  of  immersing  for  a  few 
moments  short  pieces  of  the  material  in  dilute  sulphuric  acid.  The  acid 
removes  the  scale  from  the  bar,  exposing  to  view  and  exaggating  any  surface 
defects  that  may  be  covered  by  the  scale.  Tests  pieces  of  hoop  and  file 
steel  are  pickled.  At  the  Youngstown  Upper  and  Lower  Union  Mills  all 
forging  tests  must  be  turned  in  for  the  personal  inspection  of  the  depart- 
ment superintendent,  while  the  pickle  tests  are  saved  at  the  test  house 
for  six  months  before  being  discarded.  With  hoop,  the  pickled  samples  are 
held  in  a  vise  and  the  edges  turned  over  with  a  hammer.  This  distortion 
of  the  metal  opens  up  any  laps  that  may  be  present.  On  special  section 
the  inspectors  are  required  to  save  samples  every  half  hour.  These  are 
bundled  together,  properly  tagged,  and  sent  to  the  test  house,  where  they 
are  saved  for  three  months. 

Other  Duties  of  Inspectors:  Besides  inspecting  material  for  surface 
defects,  the  mill  inspector  must  check  the  bundling  requirements  as  well 
as  the  length  of  cut.  This  practice  reduces  bundling  and  shearing  errors 
to  a  minimum.  An  hourly  report  with  carbon  copy  is  made  by  each  mill 
inspector.  This  report  shows  the  variations  in  size  of  the  bar  for  each 
hour  of  the  day.  Notations  are  made  of  any  steel  held  up  and  the  cause 
of  the  same.  These  reports  must  be  delivered  to  the  inspection  office  at  the 
end  of  each  turn.  Since  the  different  sections  are  gauged  differently,  the 
make-up  of  the  reports  will  differ  accordingly. 


496  MERCHANT  MILL  PRODUCTS 

Manner  of  Gauging  Different  Sections:  Rounds  are  gauged  on  four 
diameters,  distinguished  at  the  mill  as  top-and-bottom,  sides,  and  high  and 
low  shoulder.  By  top-and-bottom  of  a  round  is  meant  those  two  surfaces 
subject  to  compression  in  the  finishing  pass,  and  by  sides  is  meant  the 
points  opposite  the  clearance  between  the  rolls  in  this  pass.  The  shoulders 
lie  between  these  two  diameters.  The  longer  of  the  shoulder  diameters 
is  called  the  high  shoulder,  the  shorter  the  low  shoulder.  Three  samples 
are  taken  from  each  bar  gauged,  namely,  front  end,  middle  and  last  end. 
These  samples  are  taken  at  the  shears  as  the  original  bar  is  being  cut  into 
the  lengths  ordered.  The  top  and  bottom  of  a  round  may  be  distinguished 
from  the  sides  by  the  way  the  scale  is  broken  along  the  sides.  If  an  overfill 
occurs,  it  shows  also  on  the  sides  of  the  round.  Usually,  the  ends  of  a  mill 
length  of  "a  round  are  slightly  overfilled.  Flats,  squares  and  nut  steel  are 
gauged  for  width,  thickness  and  diamonding,  but  only  the  variations  in 
width  and  thickness  are  reported.  Cotton-tie,  hoop,  and  skelp  are  reported 
for  width  and  gauge  thickness.  Special  sections  are  usually  gauged  by 
means  of  templets,  but  certain  overall  dimensions  are  generally  given  on  the 
report.  A  sketch  is  sometimes  made  and  the  important  dimensions  lettered. 
The  hourly  variations  for  these  dimensions  are  then  inserted  under  the 
proper  heading.  Clip-iron,  box-strap  and  bit-mouth  are  peculiar  sections 
requiring  special  attention  for  gauging,  and  the  various  dimensions  must 
be  watched  to  get  the  section  uniform.  Inspectors  at  the  cotton-tie  mil! 
have  special  duties  to  perform.  They  must  get  from  each  buckle  machine 
every  half  hour  a  sample,  which  must  be  properly  tagged  and  taken  to 
the  department  superintendent  for  personal  inspection.  They  are  required 
to  weigh  ten  bundles  of  cotton-tie  every  half  hour  and  to  post  the  weight 
on  a  blackboard  in  plain  view  of  the  roller.  Concrete  bar  is  rolled  to 
weight,  and  inspectors  must  check  the  weights  of  the  shear  foreman.  If 
for  any  reason  an  inspector  is  not  willing  to  take  the  responsibility  of  passing 
slightly  defective  bars,  the  trucks-loaded  with  such  steel  are  marked  with 
green  tags,  signifying,  "hold  for  further  inspection."  This  steel  is  examined 
by  the  assistant  chief  inspector,  who  either  scraps  the  entire  lot  or  details 
a  specially  instructed  inspector  to  sort  the  good  from  the  bad.  Uses  for 
which  steel  is  rolled,  as  well  as  customers'  claims,  offer  guides  as  to  what 
defects  a  customer  can  accept . 


CIRCULAR  SHAPES  497 


CHAPTER  X. 

CIRCULAR  SHAPES. 

SECTION   I. 

SOME   GENERAL  FEATURES  PERTAINING  TO  THE   ROLLING  OF  CIRCULAR  SHAPES. 

The  Rolling  of  Circular  Shapes  presents  one  of  the  most  interesting 
studies  of  the  rolling  mill  industry,  because  it  is  the  latest  development 
in  rolling,  and,  though  the  idea  of  rolling  wheels  originated  in  Europe,  it 
is  in  America  that  the  art  has  been  most  highly  developed.  The  beginning 
of  this  branch  of  the  industry  dates  from  the  year  1903,  when  solid  rolled 
steel  car  wheels  were  first  used  under  freight  cars.  The  use  of  such  wheels 
resulted  from  the  introduction  in  1896  of  all  steel  freight  cars,  which  on 
account  of  their  increased  weight  and  great  carrying  capacity  required 
a  stronger  and  tougher  wheel  than  any  that  had  been  made  up  to  that  time. 
It  was  to  meet  this  requirement  that  Mr.  Charles  T.  Schoen,  who  was  the 
pioneer  in  the  manufacture  of  all  steel  cars,  perfected  the  mill,  which  now 
bears  his  name,  for  rolling  these  wheels.  Later  on,  Mr.  Schoen's  method 
of  preparing  the  steel,  which  will  be  explained  later,  was  much  improved 
by  the  Carnegie  Steel  Company,  who  purchased  this  mill  in  1908.  Con- 
sidered from  the  standpoint  of  circular  shapes  in  general,  the  Schoen  mill 
has  the  one  drawback  of  a  very  limited  product.  Being  designed  for  one 
particular  purpose,  it  can  roll  only  car  wheels,  or  wheels  of  that  class,  and 
of  these  it  is  limited  to  wheels  between  thirty  and  forty-two  inches  in 
diameter.  While  wheels  as  small  as  twenty-eight  inches  in  diameter  have 
been  made  on  this  mill,  these  smaller  sizes  are  rolled  with  much  difficulty, 
due  both  to  the  form  of  the  rolls  and  the  manner  of  rolling.  For  forming 
wheels  less  than  thirty  inches  in  diameter  the  Carnegie  Steel  Company  has 
found  that  the  forging  press  gives  the  most  satisfactory  results. 

Preparing  the  Blanks:  The  circular  shapes  all  require  a  round  blank 
to  start  with.  Mr.  Schoen  originally  sheared  his  blanks  from  slabs  with 
a  specially  constructed  punch-like  shear,  the  further  work  being  then  com- 
pleted in  much  the  same  manner  as  it  is  done  today.  But  this  method 
had  the  serious  fault  of  producing  a  wheel  in  which  the  line  of  segregation, 
or  pipe,  if  any  were  present  in  the  slab,  was  located  diametrically  across 
the  wheel  and  terminated  at  both  ends  in  the  tread.  From  what  has  already 
been  said  about  pipes  and  segregated  steel,  it  is  easy  to  see  how  this  location 
of  the  segregated  area  might  develop  defects  at  these  two  opposite  points. 
As  has  already  been  intimated,  the  Carnegie  Steel  Company  was  responsible 
for  bringing  about  the  correction  of  this  fault,  which  is  removed  by  locating 


498  THE  ROLLING  OF  STEEL 

the  segregated  line  at  the  center  and  at  right  angles  to  the  radii  of  the 
wheel,  where  the  faulty  material  may  be  punched  out  for  the  bore.  It  is 
evident  that  the  line  of  segregation  may  be  so  located  in  any  one  of  three 
ways,  namely,  by  casting  the  blanks  individually,  by  cutting  the  blanks 
from  round  or  hexagonal  ingots,  and  by  rolling  the  ingots  into  a  round 
bloom  from  which  the  blanks  may  be  sheared  or  sawed.  All  these  methods 
are  in  use  by  the  various  manufacturers  of  wheels,  but  it  would  appear 
that  the  second  and  the  third  method  should  produce  the  best  wheel,  because 
more  work  is  put  on  the  steel.  The  third  method  is  the  one  used  by  the 
Carnegie  Steel  Company.  The  round  blooms  for  the  Schoen  mills  are 
rolled  at  present  on  a  twenty-eight  inch  bloomer  at  Homestead.  Here  a 
22"  x  22"  ingot  is  slowly  and  carefully  reduced  in  from  twenty-one  to  thirty- 
one  passes  to  a  round  bloom,  eleven  or  fifteen  inches  in  diameter  for  forged 
products,  or  fifteen  inches  in  diameter  for  all  wheels  that  are  to  be  rolled 
at  Schoen.  From  the  blooming  mill,  the  bloom,  is  delivered  to  a  patented 
shear,  known  as  the  Slick  shear,  which  is  so  located,  in  conjunction  with  the 
delivery  table  and  the  manner  of  rolling,  that  first  cuts  are  made  from  that 
part  of  the  bloom  corresponding  to  the  bottom  or  butt  of  the  ingot.  This 
first  cut,  usually  about  5%  of  the  ingot,  is  just  sufficient  to  square  up  the 
butt  end  of  the  bloom  and  is  always  discarded.  The  remainder  of  the 
bloom,  excepting  the  discard  for  pipe,  is  then  cut  into  lengths  to  give  the 
proper  weight  of  metal  required  in  the  wheel,  with  an  allowance  of  ten 
pounds  over  or  under  weight,  and,  if  requested,  each  cut  is  hand  stamped 
with  a  letter  to  indicate  its  position  in  the  ingot,  starting  with  A 
for  the  first  cut  next  to  the  discard  at  the  top  of  the  ingot.  Cut  A, 
and  often  cut  B,  also,  is  used  in  making  wheels  for  the  use  of  the  Steel  Cor- 
poration only.  In  any  case  the  total  discard,  which  may  include  both  A 
and  B  cuts,  on  wheels  to  the  customer  is  never  less  than  25%,  which  amount 
is  sufficient  to  insure  sound  steel  in  the  wheels.  For  marking  the  heat 
number  and  weight  of  cut,  the  shear  is  provided  with  a  stamp  mounted 
on  the  revolving  clamp  for  the  shear  knife,  so  that  each  disc,  or  blank,  is 
plainly  stamped  with  its  heat  number  and  weight.  From  the  shears  the 
blanks  are  taken  to  a  shipping  yard,  where  they  are  carefully  inspected  for 
surface  defects,  which  are  cut  out  by  means  of  pneumatic  chipping  tools. 
Such  of  the  blanks  as  pass  this  inspection  are  then  sent  to  the  mills  to  be 
worked  into  wheels. 

SECTION  II. 

THE  CARNEGIE   SCHOEN   METHOD  FOR  MANUFACTURING   STEEL  WHEELS. 

The  Carnegie  Schoen  Method :  At  the  Schoen  plant,  which  consists 
of  three  separate  units,  the  finished  wheel  is  produced  in  several  stages, 
the  number  of  which  depend  upon  the  kind  of  wheel,  the  unit  in  which  it 
is  made,  and  the  working  conditions  of  the  heating  furnaces.  Upon  receipt 
of  the  blanks  at  the  plant,  they  are  check  weighed,  and  the  heat  number 
of  each  blank  as  well  as  the  letter  indicating  its  position  in  the  ingot  are 


CIRCULAR  SHAPES  499 


all  recorded  in  the  form  of  a  serial  number.  The  blanks  are  then  charged 
in  order  into  a  reheating  furnace,  where  they  remain  for  about  two  and 
one-half  hours.  In  the  older  units,  mills  number  one  and  two,  the  reheating 
furnaces  are  all  of  the  regenerative  type  and  use  producer  gas;  but  in  the 
most  recent  mill,  or  number  three,  the  first  furnace  is  of  the  continuous 
type,  the  bottom  of  which  is  inclined  sufficiently  to  cause  the  blanks  to 
roll  down  from  the  feeding  end  as  rapidly  as  they  are  removed  at  the  drawing 
end.  This  type  of  furnace  heats  the  discs  very  slowly  and  gradually, 
because  it  is  intended  merely  to  give  the  discs  a  preliminary  heating,  and 
its  temperature  is  therefore  low.  At  the  drawing  end,  the  temperature  is 
maintained  at  about  800°  C.  After  being  subjected  to  this  preliminary 
heating,  the  discs  are  transferred  to  a  regenerative  furnace  for  the  final 
heating  previous  to  forging.  When  the  discs  have  reached  the  proper 
temperature,  they  are  withdrawn  from  the  furnace  and  taken  to  the  forging 
presses  where  each  is  forged  to  a  shape  resembling  that  of  the  finished 
wheel  before  dishing  or  coning.  As  to  dimensions,  this  forged  blank  is 
from  four  to  five  inches  under  size  in  diameter,  some  three-fourths  inch 
over  size  in  that  part  of  the  web  near  the  rim,  somewhat  oversize,  also, 
in  depth  of  rim,  a  little  oversize  in  width  of  rim,  but  of  correct  or  slightly 
full  size  in  the  hub  and  a  small  part  of  the  web  next  to  the  hub. 

Forging  the  Blanks— First  Method:  The  forging  may  be  done  in 
one  heat  or  two  heats  and  on  one  press  or  on  two  different  presses.  When 
two  heats  are  used,  two  presses  are  usually  employed  for  the  forging.  In 
this  method,  the  disc  is  cleaned  of  scale  on  its  two  ends  and  then  placed 
vertically  in  the  first  press,  where  it  is  first  perfectly  centered  by  two 
arms  which  engage  it  from  opposite  sides  of  the  press  and  so  support  it  till 
the  top  die  has  descended  upon  it.  In  this  press  the  bottom  die  corresponds 
to  the  outside  face  of  the  wheel  while  the  top  die  is  plain,  but  may  be  slightly 
convex  to  cause  a  radial  flow  of  the  metal  in  taking  the  shape.  The  pressure, 
applied  in  successive  steps  by  means  of  accumulators  and  intensifier,  starts 
with  about  700  pounds  per  square  inch,  then  increases  to  2500  pounds  and, 
finally,  to  as  much  as  4500  pounds  per  square  inch,  if  needed.  At  the  begin- 
ning, the  scale  is  cracked  from  the  disc  and  falls  into  the  bottom  die,  from 
which  it  is  blown  by  means  of  a  steam  jet,  in  order  to  avoid  pitting  the 
surface  of  the  blank.  This  pressing  is,  in  itself,  a  severe  test  upon  the 
metal,  and  any  flaws,  such  as  seams  or  cracks,  are  sure  to  be  exposed, 
although  they  seldom  occur.  When  such  flaws  do  develop,  the  blank  is 
scrapped  at  this  press.  The  perfect  blanks  are  now  placed  in  a  second 
reheating  furnace,  where  their  temperature  is  equalized  and  brought  again 
to  the  forging  point.  When  these  conditions  have  been  attained,  the  blank 
is  cleaned  of  scale  and  placed  in  a  second  press,  in  which  the  top  die  con- 
forms to  the  shape  of  the  inside  face  of  the  wheel.  Before  applying  the 
pressure,  a  little  fine  coal  is  thrown  on  the  bottom  die  and  upon  the  blank 
to  prevent  the  dies  sticking  and  to  keep  their  surfaces  smooth.  After  this 
forging,  the  blank  is  placed  in  a  third  press,  where  the  bore  is  punched. 


500  THE  ROLLING  OF  STEEL 


During  the  punching,  the  hub  of  the  wheel  is  supported  in  neatly  fitting 
dies  in  order  to  avoid  forcing  this  part  of  the  wheel  out  of  shape. 

In  the  Second  Method  of  Forging,  the  press  is  provided  with  the  two 
top  dies  mentioned  in  connection  with  the  two  presses  used  in  the  first 
method.  These  dies  are  mounted  upon  a  sliding  frame  in  such  a  manner 
that  either  may  be  brought  at  will  beneath  the  piston  of  the  press,  thereby 
dispensing  with  the  first  forging  press  and  permitting  the  forging  to  be 
accomplished  in  one  operation  when  the  conditions  are  favorable.  Thus,. 
if  the  blank  is  at  a  temperature  sufficiently  high  and  is  evenly  heated  through- 
out, the  second  top  die,  conforming  to  the  inside  of  the  wheel,  is  brought  over 
the  blank,  and  the  forging  is  completed  in  a  single  stage.  If  the  conditions 
are  such  as  are  likely  to  cause  an  uneven  flow  of  the  metal,  which  results 
if  the  blanks  are  unevenly  heated,  the  plain  die  is  used  first,  then  the  inside 
die  is  moved  into  position  and  the  pressure  applied,  thus  forming  the  blank 
in  two  stages,  but  on  a  single  heating.  The  bore  is  then  immediately 
punched  as  in  the  first  method.  After  the  forging,  by  whichever  method 
that  may  have  been  used,  and  the  punching  of  the  bore,  the  blank  is  placed 
in  a  reheating  furnace  where  it  remains  until  it  has  reached  the  proper 
temperature  for  rolling. 

The  Rolling  Mill :  The  two  older  mills  are  very  similar  in  every  detail 
of  their  construction,  but  in  the  number  three  mill,  which  made  its  first 
trial  rolling  June  5th,  1917,  a  few  changes  looking  toward  an  improvement 
in  construction  over  the  older  mills  have  been  made.  For  this  reason  this 
mill,  rather  than  either  of  the  older  ones,  will  be  described.  This  descrip- 
tion is,  however,  made  rather  brief,  for  the  mill,  itself,  is  a  somewhat 
complicated  piece  of  machinery,  as  the  reader  will  surmise  when  he  is  told 
that  seven  rolls  play  upon  the  wheel  at  one  time  during  the  rolling.  These 
rolls  consist  of  one  tread  roll,  two  web  rolls,  and  four  (2  sets)  rim  rolls, 
and  are  supported,  together  with  all  their  bearings,  pinions,  or  gears, 
adjusting  screws,  levers,  etc.,  in  one  pair  of  horizontal  housings,  which  are 
large  steel  castings  and  placed  one  above  the  other.  The  bottom  housing 
lies  directly  upon  the  mill  foundation  and  forms  the  support  for  the  rolls 
and  for  the  top  housing  some  four  feet  above  it.  The  housings  are  held 
apart  by  suitable  pillars  or  posts  and  are  bound  firmly  together  by  means 
of  immense  bolts.  Between  these  housings  the  rolls  are  located;  they  may 
be  described  as  follows:  The  largest  roll  is  the  tread  and  flange  roll.  In 
form  it  resembles  a  wheel,  some  thirty-three  inches  in  diameter,  and  is  so 
located  back  near  the  central  point  of  the  housings  that,  during  the  rolling, 
it  revolves  in  the  same  vertical  plane  as  the  wheel  and  bears  upon  its  tread 
from  the  rear.  Its  face  is  somewhat  wider  than  the  rim  of  the  wheel  and 
is  grooved  to  correspond  to  the  'tread  and  flange.  It  is  friction  driven 
and  is  carried  on  a  slide  bearing,  so  that,  by  means  of  a  screw,  connecting 
the  sliding  box  to  a  fixture  at  the  rear  of  the  housings  and  operated  through 
a  worm  shaft  and  gear  by  means  of  a  15  h.  p.  electric  motor  located  on 


CIRCULAR  SHAPES 


501 


FIG.  100.     Drawing  of  Schoen  Mill  Showing  Wheel  with  Web,  Tread,  and  One  Set 
Rim  Rolls  in  Position  at  End  of  the  Rolling  Operation. 


502  THE  ROLLING  OF  STEEL 


top  of  the  upper  housing,  this  roll  may  be  moved  backward  or  forward  at 
the  will  of  the  operator.  Few  operators,  however,  move  this  roll  after  the  mill 
is  once  adjusted  to  roll  the  wheels  of  a  given  size  and  type.  On  the  opposite 
sides  of  the  tread  roll  are  located  the  two  web  rolls.  They  are  about  three 
feet  in  length,  lie  in  a  horizontal  position  and  extend  inward,  so  that  their 
center  lines  form  angles  of  nearly  30°  with  the  center  line  of  the  mill  and 
intersect  at  a  point  near  the  center  of  the  wheel  that  is  being  rolled.  On 
their  front  ends  they  carry  the  rolling  heads,  or  surfaces,  which  conform 
to  the  shape  of  the  wheel  beneath  the  rim,  while  their  rear  ends  are  anchored 
in  rotating  coupling  boxes.  Light  steel  spindles,  some  five  feet  in  length 
and  provided  with  proper  wobblers,  connect  these  couplings  to  the  two 
bevel  gears,  one  of  which  stands  on  each  side  of  the  mill  at  the  rear.  These 
gears  mesh  into  similar  gears  mounted  on  the  driving  shaft  of  a  750  h.  p. 
D.  C.  motor  (500  volts,  1100  amperes,  130  r.  p.  m.),  which,  located  at  the 
rear  and  on  the  center  line  of  the  mill,  is  used  to  drive  these  rolls.  Just 
back  of  the  rolling  heads,  these  rolls  are  supported  in  sliding  bearings 
which  permit  of  their  being  spread  as  desired.  The  pressure  for  rolling 
is  transmitted  to  these  bearings  through  radial  levers,  the  long  arms  of 
which  are  each  attached  above  the  housings  to  the  same  screw,  so  that  the 
same  motion,  but  opposite  in  direction,  and  equal  pressures  are  imparted  to 
the  two  rolls  at  the  same  time.  This  screw,  which  corresponds  to  the 
adjusting  screws  on  ordinary  mills,  is  actuated  by  means  of  a  15  h.  p.  direct 
current  motor  (220  volts,  64  amperes,  550  r.  p.  m.).  By  this  means,  the 
power  of  the  motor  is  multiplied  many  times  and  is  capable,  at  its  maximum, 
of  exerting  such  pressure  on  the  web  rolls  as  to  stall  the  mill.  As  to  the 
relative  altitude  of  these  three  rolls,  they  are  so  placed  that  their  lines  of 
contact  with  the  wheel  in  rolling  and  the  axis  of  the  wheel,  itself,  all  lie  in 
the  same  horizontal  plane.  The  four  rim  rolls,  which  are  friction  driven, 
are  located,  one  pair  above  and  one  pair  below,  the  web  rolls,  so  that  all  the 
rolls  lie  within  an  arc  of  180°  of  the  circumference  of  the  wheel  being  rolled. 
These  rolls  are  approximately  twelve  inches  in  length  and  nine  inches  in 
diameter,  and  are  so  placed  that  the  projected  axes  of  rotation  of  the  two 
on  either  side  of  the  wheel  intersect  at  the  axis  of  rotation  of  the  wheel. 
They  are  mounted  upon  sliding  frames  attached  to  the  front  of  the  mill 
housings.  These  four  frames  are  moved  by  horizontal  screws  connected 
by  vertical  worm  shafts  and  gears  to  a  common  shaft,  which  extends  in 
front  of  and  beneath  the  housings  and  is  operated  by  an  electric  motor  set 
some  eight  or  ten  feet  to  the  right  of  the  mill,  measuring  from  the  side  of 
the  housings.  In  this  way  the  spread  of  these  rolls  is  made  uniform.  How- 
ever, the  bottom  set  of  rim  rolls,  due  to  the  manner  of  rolling,  do  nearly 
all  the  work.  An  indicator,  mounted  on  the  upper  horizontal  screw  attached 
to  the  sliding  frame  on  the  right  side  of  the  mill,  is  in  plain  view  of  the 
operator,  who  is  able,  by  this  means,  to  read  the  spread  of  the  rolls  and  thus 
control  the  width  of  the  rim.  These  rolls  may  be  so  formed  that  they  will 
roll  the  sides  of  the  rim  at  a  slight  angle  to  the  vertical,  so  that  these  surfaces 


CIRCULAR  SHAPES  503 


will  lie  in  parallel  planes  after  the  dishing,  or  coning,  process.  Two  shelves 
attached  to  the  housings  in  front  of  the  tread  and  web  rolls  and  separated 
by  a  space  a  little  greater  than  the  thickness  of  the  wheel  at  the  hub,  gives 
a  support  for  the  wheel,  which  is  mounted  on  a  loosely  fitting  mandrel 
during  the  rolling.  This  mandrel  is  provided  with  removable  bearings, 
which  rest,  unattached,  upon  the  shelves,  thus  leaving  the  wheel  free  to 
move  forward  after  the  rolls  have  gripped  it. 

The  Rolling  Process:  After  the  forged  blank  has  attained  the  proper 
temperature  for  rolling,  it  is  removed  from  the  furnace  and  carried  to  the 
mill  with  a  charging  and  drawing  machine,  where  it  is  gripped  beneath 
the  rim  by  tongs  suspended  by  a  small  jib  crane  standing  on  the  housing 
above  the  rolls.  The  wheel,  held  vertically  by  the  crane,  is  guided  between 
the  two  supporting  shelves,  and  the  mandrel  is  inserted  through  the  punched 
bore.  The  crane  tongs  are  then  released,  and  the  wheel,  resting  on  the 
mandrel,  is  pushed  back  by  hand  against  the  tread  roll  and  into  the  position 
for  rolling.  The  web  and  rim  rolls  are  then  brought  to  bear  on  the  wheel, 
the  latter  rather  lightly  at  first.  The  large  driving  motor  is  started,  and 
the  wheel  is  made  to  revolve  by  the  action  of  the  web  rolls  upon  it.  These 
rolls,  working  upon  both  sides  of  the  web  and  the  under  side  of  the  rim, 
force  the  metal  back  into  the  groove  of  the  tread  roll  with  considerable 
pressure,  until  this  part  of  the  wheel  has  reached  the  dimensions  for  which 
the  mill  is  set,  or  the  diameter  desired,  while  the  spread  of  the  metal  and 
the  width  of  the  rim  is  controlled  by  pressure  applied  to  the  four  rim  rolls. 
The  diameter  of  the  wheel  is  ascertained  by  means  of  a  gauge,  or  caliper, 
one  end  of  which  is  attached  to  the  tread  roll  housing.so  that  it  is  moved  simul- 
taneously with  this  roll,  in  the  same  direction  and  through  the  same  space. 
The  other  end  of  the  caliper  projects  in  front  of  the  mill,  and  is  provided 
with  a  hinged  arm  or  pointer,  so  that  it  may  be  raised  out  of  the  way  for 
inserting  the  blank  or  removing  the  wheel.  The  end  of  this  pointer  is 
curved  toward  the  mill  at  right  angles  to  its  length.  At  the  beginning  of 
the  rolling,  the  roller  lowers  this  pointer  to  rest  on  the  left  hand  shelf,  in 
which  position  its  curved  end  extends  toward  the  tread  roll  and  is  opposite 
its  line  of  contact  with  the  wheel,  the  pointer  having  been  adjusted  so  that 
the  distance  between  its  point  and  the  tread  roll  is  equal  to  the  diameter 
of  the  wheel  desired.  With  the  rolling,  the  wheel  increases  in  diameter 
and  moves  forward  on  the  loose  sliding  mandrel  until  a  circle  on  the  center 
of  its  tread  comes  in  contact  with  this  pointer,  when  the  roller  stops  the 
mill  and  spreads  the  rolls  for  the  release  of  the  wheel.  During  the  rolling, 
jets  of  water  are  directed  against  the  surfaces  being  rolled  to  remove  the 
scale  and  give  a  smooth  finish  to  the  wheel.  In  addition  to  the  water, 
a  salt  jet  i.3  also  directed  against  the  tread.  The  actual  rolling  process 
requires  about  one  minute,  so  that  the  maximum  capacity  of  the  mill  is 
more  than  500  wheels  per  day  of  twenty-four  hours.  However,  on  account 
of  the  care  exercised  to  assure  a  high  quality  of  product,  these  mills  are 
operated  at  only  50  to  60%  of  their  capacity. 


504  THE  ROLLING  OF  STEEL 

Effect  of  the  Rolling :  It  will  be  observed  that  all  the  work  of  the  rolling 
is  concentrated  upon  the  outer  part  of  the  web  and  the  rim,  where  the 
additional  refinement  due  to  rolling  is  most  needed.  This  refinement  is 
very  marked,  as  is  shown  by  Brinell  tests  on  sections  of  the  wheel  and  by 
the  visible  difference  in  the  structure  of  the  metal  between  the  hub  and 
rim.  This  effect  is  most  marked  on  the  tread,  where  the  hardness  of  the 
metal  and  closeness  of  grain  can,  no  doubt,  be  considerably  increased  by 
rolling  at  low  temperature  or  by  chilling  the  metal  by  using  an  increased 
amount  of  water  during  the  rolling.  However,  as  such  practice  is  likely 
to  cause  spalling,  it  is  not  employed  by  the  operators.  As  machining  the 
tread  removes  much  of  this  super-refined  metal,  it  would  appear  that  the 
wheel  rolled  to  a  finish  should  be  far  superior  in  wearing  properties  to  the 
machined  wheel,  on  first  run,  at  least.  Evidence  of  this  fact  is  Seen  in  the 
increasing  demand  for  rolled  to  finish  wheels  for  passenger  cars,  even  where 
formerly  only  machined  treads  were  used.  The  mill  practice  on  rolled  to 
finish  wheels  is  high,  but  a  greater  or  less  number  of  the  wheels  require 
machining  in  order  to  eliminate  slight  surface  defects  or  true  up  the  dimen- 
sions. 

Punching  Web  Holes  and  Coning:  After  the  rolling,  the  wheel  is 
taken  on  a  buggy  to  a  small  press,  where  the  web  holes  are  punched,  when 
these  are  required.  This  press  is  fitted  to  punch  either  two  or  four  holes, 
one  and  three-fourths  inches  in  diameter,  and  equally  spaced  on  radii  of 
8;Mj,  9*4,  10,  11,  or  12  inches,  which  are  standard  radii  for  all  the  different 
sizes  of  wheels.  From  the  punching  press,  or  from  the  rolling  mill,  if  web 
holes  are  not  required,  the  wheel  is  taken  to  the  coning  press,  being  hot 
stamped  in  transit  with  the  word  Carnegie  on  the  inner  surface  of  the  web. 
This  press  is  provided  with  dies  which  conform  to  the  exact  contour  of  the 
finished  wheel,  the  top  die  corresponding  to  the  inside  of  the  wheel.  For 
preserving  the  rotundity  of  the  wheel,  the  bottom  die  is  surrounded  with 
a  series  of  tread  blocks  in  the  form  of  segments  of  a  circle,  while  the  top 
die  is  similarly  provided  with  a  tapered  ring  to  fit  over  these  segments. 
Thus,  when  the  dies  are  brought  together  for  coning,  this  ring  slips  over 
the  outside  of  the  segments  and  forces  them  firmly  against  the  tread  while 
the  coning  or  dishing  is  being  effected.  As  these  blocks  leave  slight  im- 
pressions on  the  tread  where  adjoining  blocks  meet,  the  wheel  is  turned 
through  an  arc  of  a  few  degrees  and  again  subjected  to  the  pressure,  which 
removes  all  but  traces  of  these  marks,  except  in  occasional  cases  where 
they  are  unusually  deep.  Upon  removal  from  this  press,  the  wheel  is  hot 
stamped  with  a  mill  serial  number,  the  heat  number  and  the  date,  then 
it  is  passed  to  the  cooling  bed. 

Inspection  of  Carnegie  Schoen  Wheels  is  very  rigid.  When  cold,  the 
wheel  is  rolled  to  the  inspection  platform  for  its  initial  inspection.  This 
inspection  covers  surface  defects,  location  of  the  hub,  rotundity  of  tread, 
and  the  size,  which  is  measured  in  Carnegie  Standard  tape  sizes.  These 


CIRCULAR  SHAPES 


505 


A.    The  Blank. 


B.     Blank  after  First  Forging. 


C.     Blank  after  Second  Forging. 


D.      Wheel,  after  Punching,  Rolling  and  Coning. 
FIG.  101.     Sketches  Illustrating  the  Manufacture  of  Car  Wheels  by  the  Carnegie-Schoen  Method. 


506  THE  ROLLING  OF  STEEL 


tapes  are  graduated  in  eighth's  of  an  inch,  beginning  with  seven  feet  for  a 
zero  mark.  The  surface  defects  consist  principally  of  over-fills,  under-fills, 
slivers,  scale  pits,  and  block  marks,  and  as  they  are  seldom  deep,  they  may 
be  removed  by  machining.  The  tape  size  and  all  defects  are  plainly  marked 
on  each  wheel,  the  former  with  a  stencil,  the  latter  in  chalk.  After  this 
preliminary  inspection,  the  wheels  are  machined  as  required  to  meet  the 
specifications  or  remove  the  defects.  On  rolled  to  finish  wheels,  the  machin- 
ing consists  of  rough  boring  and  facing  of  the  hub  and  cutting  in  the  limit 
of  wear  circle  on  the  outside  of  the  rim.  The  wheels  are  then  rolled  back 
to  the  platforms  for  final  inspection,  which  is  even  more  rigid  than  the  first. 
In  this  inspection  the  wheels  are  tested  for  size,  eccentricity  and  size  of 
bore,  position  and  size  of  hub,  thickness  and  height  of  flange,  radius  of 
throat,  thickness  of  rim,  coning,  rotundity,  and  soundness.  After  being 
re-stenciled  with  tape  size  and  marks  requested  by  the  customer,  such  wheels 
as  come  within  the  allowable  tolerances  are  mated  and  sent  to  the  shipping 
platform. 

Heat  Treating  Car  Wheels:  Heat  treating  is  a  recent  innovation  in 
the  manufacture  of  car  wheels,  and  may  be  said  to  be  still  in  the  experi- 
mental stage.  Owing  to  the  irregular  section  of  the  wheel,  quenching  is  a 
difficult  process,  because,  if  the  entire  wheel  is  quenched,  the  uneven  cooling 
of  the  heavy  and  light  parts  set  up  stresses  in  the  shape  that  result  in  the 
destruction  of  the  wheel.  In  order  to  overcome  this  tendency,  the  Carnegie 
Steel  Company's  research  department  has  developed  a  method  whereby  the 
rim  only  is  quenched,  after  which  the  wheel,  before  the  hub  and  web  have 
cooled,  is  given  a  drawback  at  a  suitable  temperature  under  the  lower 
critical  range.  If  the  hub  and  web  are  cooled  in  air  after  the  quenching  of 
the  rim,  the  wheels  show  a  dangerous  tendency  to  crack  by  this  method,  also, 
hence  the  quick  draw  back.  From  an  economical  point  of  view,  it  would 
appear  that  the  cheapest  plan  would  be  to  quench  the  wheel  on  the  rolling 
heat,  but  on  account  of  unavoidable  variations  in  the  finishing  temperature 
this  treatment  was  found  to  be  unsatisfactory.  The  wheels,  therefore,  are 
allowed  to  become  cold  after  rolling  and  coning,  when  they  are  reheated 
above  their  critical  range  before  quenching.  This  process  is  accomplished 
in  a  rectangular  tank  provided  with  rollers  grooved  to  conform  to  the 
tread  and  flange  and  so  placed  in  the  tank  that  they  support  the  wheel 
in  a  vertical  position  transverse  to  the  tank,  which  contains  enough  of  the 
quenching  fluid  to  cover  the  rim  only.  With  the  rollers,  which  are  mounted 
on  a  shaft  connected  to  a  motor,  revolving,  the  wheel,  at  the  proper  tem- 
perature, is  placed  in  position  on  the  rollers,  which  immediately  start  the 
wheel  revolving,  or  spinning,  also.  The  spinning  is  continued  until  the  rim 
becomes  sufficiently  cooled  when  it  is  withdrawn  and  immediately  given  a 
draw  back,  as  stated  above.  The  process  adds  considerable  to  the  cost  of 
the  wheel,  and  though  there  are  many  wheels  in  service  thus  treated,  and 
apparently  with  promising  results,  sufficient  time  has  not  yet  elapsed  to 
determine  just  to  what  extent  the  wheels  are  improved  by  the  treatment. 


CIRCULAR  SHAPES  507 

The  Forging  of  Circular  Shapes :  As  previously  indicated,  only  those 
circular  shapes  which  are  more  than  thirty  inches  in  diameter  can  be 
finished  by  rolling  on  the  Schoen  mill.  However,  this  plant,  which 
represents  the  circular  shape  department  of  the  Homestead  works,  produces 
a  great  number  of  smaller  circular  shapes  by  forging  only.  These  smaller 
shapes  include  such  articles  as  wheels  for  low  type  street  cars;  double 
flanged  crane  track  wheels;  automobile  fly  wheels;  turbine  discs;  shaft 
couplings;  pipe  flanges;  pistons  for  locomotives;  gear  rings;  and  gear  blanks 
for  automobiles,  farm  tractors,  turbo  generators,  street  cars,  etc.  In  addi- 
tion to  these,  a  miscellaneous  lot  of  circular  shapes  ranging  in  form  from 
the  most  intricate  sections  to  plain  discs,  and  in  sizes  from  twenty-five 
pounds  to  five  hundred  and  even  a  thousand  pounds  are  produced.  For 
forming  all  these  shapes  the  same  powerful  presses  are  employed  as  are 
used  in  preparing  the  rolled  wheel  blanks,  and  in  general  the  methods  of 
forging  are  similar,  with  the  exception  that  additional  precautions  in  the 
removal  of  scale  before  forging  are  observed.  In  this  connection  it  should 
be  noted  that  forging  will  not  produce  the  smooth  finish  obtained  by  rolling 
on  the  Schoen  mill,  and  all  forged  articles  requiring  a  perfectly  smooth 
surface  must  be  machined  to  finish. 


508  FORGING  OF  AXLES,  SHAFTS,  ETC. 


CHAPTER  XI. 

FORGING  OF  AXLES,  SHAFTS  AND  OTHER  ROUND  SHAPES. 

SECTION   I. 

HOWARD   AXLE  WORKS   AS  AN  EXAMPLE  OF  A  FORGING   SHOP. 

The  Plant  and  Its  Equipment:  Aside  from  the  forging  of  armor 
plate  and  other  articles  required  by  our  government,  small  wheels  and  a 
miscellaneous  lot  of  shapes  for  its  own  use,  the  Carnegie  Steel  Company  has 
restricted  its  market  activity  in  the  forging  line  to  the  manufacture  of 
axles,  shafts  and  similar  heavy  products.  For  these  products  the  company 
operates  a  plant  especially  designed  for  the  work,  known  as  the  Howard 
Axle  Works,  which  may  be  taken  here  as  an  example  of  a  modern  forging 
plant.  The  essential  equipment  of  the  plant  includes  three  continuous  coal 
fired  furnaces  for  heating  the  blooms,  a  twenty-four  inch  roughing  mill  of 
two  stands  of  rolls  in  tandem,  ten  7000  pound  and  two  7500  pound  double 
acting  steam  forging  hammers,  three  gag  press  straighteners,  thirty  double 
cutting-off  and  centering  machines,  twenty-seven  rough  turning  lathes,  two 
finishing  lathes,  one  boring  lathe,  two  hollow  drill  machines,  and  a  complete 
heat  treating  plant  that  will  be  described  more  in  detail  later.  The  forging 
limits  of  the  plant  as  to  size  is  as  follows:  Maximum  weight,  2500  pounds; 
maximum  length,  ten  feet;  maximum  diameter,  twelve  inches;  minimum 
diameter,  three  inches.  As  to  arrangement,  the  layout  of  the  plant  provides 
for  the  most  economical  handling  of  the  materials.  The  blooms  start  in 
at  one  end  of  the  plant  and  continue  in  one  direction,  progressing  step  by 
step  through  the  various  operations,  until,  upon  arrival  at  the  other  end  of 
the  plant,  they  are  in  a  form  ready  for  shipment. 

Precautions  to  be  Observed  in  the  Manufacture  of  Axles:     As  the 

failure  of  an  axle  in  service  usually  results  with  serious  consequences,  great 
responsibility  rests  upon  the  manufacturer  at  all  times  to  see  that  each 
and  every  axle  is  as  nearly  perfect  as  it  is  possible  to  make  it.  Before 
describing  the  processes  of  manufacture,  it  may  be  well  to  point  out 
some  of  the  things  that  may  cause  axles  to  fail,  because  the  thing  aimed 
at  in  developing  a  method  of  manufacture  is  the  elimination  of  as  many 
of  the  causes  of  failure  as  possible.  There  are  many  of  these  causes  of 
failure,  according  to  some  writers  upon  the  subject,  but  the  majority  may 
be  traced  to  the  following,  which  are  to  be  looked  upon  as  the  chief  sources 
of  danger:  1.  Pipe;  2.  Segregation;  3.  Unequal  or  improper  heating; 
4.  Slag  inclusions;  5.  Forging  strains;  6.  Incipient  cracks.  From  this 
list  it  is  seen  at  a  glance  that  some  of  these  sources  of  danger  are  very 


INSPECTING  AND  HEATING  BLOOMS  509 


difficult  to  eliminate  and  that  the  making  of  a  good  axle  must  begin  with 
the  making  of  the  steel,  itself.  The  other  defects  may  be  overcome  by 
proper  attention  to  details  during  the  processes  of  rolling  and  forging  the 
steel.  Starting  with  the  steel  after  it  has  been  rolled  into  blooms,  which 
must  correspond  in  dimensions  and  weight  to  the  size  of  the  axles  it  is 
intended  for,  the  various  steps  in  the  process  of  manufacture  at  these  works 
are  as  follows: 

Inspection  of  the  Blooms:  Located  at  Homestead,  Pa.,  the  Howard 
Works  receives  its  steel  from  the  Homestead  Steel  Works  at  Munhall. 
Here,  before  the  steel  is  shipped  to  the  axle  works,  the  blooms  are  subjected 
to  a  rigid  inspection.  Those  blooms  that  show  any  signs  of  pipe  or 
insufficient  discard  at  the  blooming  mill  shears  are  rejected.  Surface 
defects,  such  as  seams,  slivers  and  surface  cracks,  are  carefully  chipped 
out,  and  those  blooms  in  which  the  defects  extend  beyond  certain  deptns, 
or  occur  on  the  part  that  corresponds  to  the  wheel  seat  are  also  discarded. 
Such  blooms  as  pass  the  inspection  are  shipped  to  the  axle  works,  where 
they  are  stored  under  cover  until  needed. 

Heating  the  Blooms:  The  proper  heating  of  the  blooms  for  forging 
requires  that  they  be  uniformly  heated  throughout  and  be  brought  grad- 
ually to  the  forging  temperature,  which  should  be  kept  as  low  as  possible 
and  yet  permit  the  work  to  be  done.  The  advantages  of  a  low  finishing 
temperature  in  securing  maximum  grain  refinement  is  readily  understood. 
The  importance  of  heating  slowly  is  also  realized,  when  it  is  pointed  out 
that  rapid  heating  may  cause  the  outside  of  the  bloom,  which  is  first  to 
rise  in  temperature,  to  expand  away  from  the  more  slowly  heating  core  and 
thus  cause  ruptures  that  may  not  be  welded  up  by  the  action  of  the  hammers. 
Slow  heating  gives  the  heat  a  chance  to  "soak"  into  the  bloom,  thus  giving 
that  uniformity  in  temperature  from  center  to  surface  so  necessary  to  secure 
a  finished  forging  of  the  best  quality.  As  to  the  proper  temperature,  the 
manufacturer  has  always  had  to  depend  upon  the  eye  and  judgment  of  the 
trained  heater  in  the  past,  and  must  continue  to  do  so  to  a  great  extent  in 
the  future.  The  use  of  pyrometers  does  not  replace  this  human  element, 
because  the  pyrometer  records  the  temperature  of  the  furnace  and  not  of 
the  steel,  particularly  in  the  case  of  the  continuous  furnace.  The  rate  of 
heating  is  fixed  by  the  type  of  furnace.  At  these  works,  therefore,  the 
continuous  furnace  is  used  because  this  type  heats  up  the  steel  very  grad- 
ually. The  bloom  is  placed  in  the  furnace  at  the  cold  end  and  is  slowly 
pushed  toward  the  hot  end,  so  that  it  reaches  a  full  forging  temperature 
only  a  short  time  before  it  is  drawn  from  the  furnace. 

The  Rolling  and  Forging  Operation:  Having  been  brought  to  the 
proper  temperature  for  forging,  the  blooms,  within  a  certain  range  of  sizes, 
are  pushed  out  of  the  hot  end  of  the  heating  furnaces  upon  a  conveyor, 
which  serves  all  three  furnaces,  and  are  carried  by  it  to  the  rolling  mill. 


510  FORGING  OF  AXLES,  SHAFTS,  ETC. 

This  mill  consists  of  two  stands  of  rolls  in  tandem,  as  previously  stated. 
Each  stand  is  provided  with  four  passes  cut  to  take  four  different  sizes  of 
square  blooms.  These  sizes  are  6*/£,  7}/£,  8  and  8^  inches.  The  passes 
are  shaped  to  round  off  the  corners  of  the  bloom,  to  secure  which  result 
is  the  main  object  in  the  use  of  the  mill.  The  reduction  in  cross  sectional 
area  due  to  the  rolling  varies  from  33/£%  to  5%.  From  the  mill,  a  roll 
table  distributes  the  blooms  to  the  hammers,  which  are  arranged  in  two 
rows,  one  on  each  side  of  the  table.  Adjustable  deflecting  rails  built  in 
the  side  guards  of  the  table  serve  to  divert  the  blooms  to  small  receiving 
tables,  of  which  there  is  one  for  each  hammer,  and  leave  them  in  positions 
to  be  most  conveniently  grasped  by  the  hammer  tongs,  which  are  suspended 
from  cranes.  The  tongs  having  been  quickly  clamped  on,  the  bloom  is 
swung  around  between  the  forming  dies  of  the  hammer.  These  dies  are 
provided,  when  desired,  with  two  or  more  grooves;  one,  the  plain  groove 
used  to  do  the  greater  part  of  the  forging,  is  located  directly  under  the 
piston  rod,  while  the  other  grooves,  used  to  form  special  sections,  such  as 
the  journals,  are  placed  beside  the  plain  groove.  The  forging  is  begun  at 
the  middle  of  the  bloom,  which  is  rapidly  reduced  by  heavy  blows  of  the 
hammer,  the  forging  progressing  toward  the  free  end  of  the  bloom.  Here, 
by  the  special  grooves  in  the  die,  the  journal  or  other  special  section  is 
formed  by  a  few  strokes,  when  the  piece  is  again  placed  in  the  plain  groove, 
and  the  forging  is  smoothed  up  and  brought,  by  light  strokes  of  the  hammer, 
to  correct  diameter,  which  is  determined  by  caliper.  The  tup  is  then 
brought  to  rest  upon  the  axle,  which  is  held  between  the  dies  while  tho 
tongs  are  released,  and  those  on  the  opposite  side  of  the  hammer  are  made 
fast  to  the  finished  end.  The  other  end  of  the  axle  is  then  forged  down 
like  the  first,  except  that,  in  addition  to  diameter,  the  length  is  also  fixed. 
The  crane  is  then  swung  around,  and  the  axle  is  placed  on  the  cooling  bed, 
where  it  is  supported  about  three  feet  above  the  floor  by  two  rails,  which 
arrangement  allows  it  to  be  cooled  uniformly  by  the  air.  The  average 
reduction  in  cross  sectional  area  under  the  hammer  is  about  50%.  Forgings 
requiring  blooms  larger  than  eight  and  one-half  inches  are  reduced  entirely 
by  hammer.  Two  crews,  each  made  up  of  a  hammerman,  who  has  charge 
of  the  forging,  and  three  helpers,  and  one  hammer  driver,  are  assigned  to 
each  hammer.  The  crews  work  alternately,  each  crew  completing  one  axle 
at  a  time. 

Advantages  of  the  Method:  Aside  from  the  increased  tonnage  made 
possible  by  the  rapidity  of  the  work,  the  method  of  forging  employed  at 
Howard  presents  many  advantages  which  bear  directly  upon  the  quality 
of  the  product.  The  rolling  mill,  which  accomplishes  only  a  small  fraction 
of  the  total  work  done  upon  the  axle,  is  a  great  help  to  the  hammers.  By 
rounding  off  the  corners  of  the  bloom,  it  practically  eliminates  all  danger 
of  forming  hammer  laps,  and  permits  the  forging  to  be  accomplished  in  the 
shortest  time  possible.  Hence  a  low  initial  temperature  can  be  used  for 
forging,  and  the  work  can  be  completed  at  a  more  uniform  temperature. 


FINISHING  PROCESSES  511 


This  uniformity  of  the  finishing  temperature  is  a  very  noticeable  feature 
at  Howard.  Thus,  in  observing  closely  various  axles  at  different  stages 
of  the  forging  operation  the  eye  can  detect  little  difference  in  temperature 
between  those  axles  on  which  the  forging  has  just  begun  and  those  that 
are  being  finished.  That  this  rapid  method  of  forging  on  one  heat  is  far 
superior  to  the  old  method  of  forging  on  two  heats  is  apparent,  because 
it  not  only  promotes  greater  uniformity  in  individual  axles  but  eliminates, 
to  a  far  greater  degree,  the  variation  in  different  axles. 

SECTION  II. 

FINISHING   PROCESSES   FOR  FORGINGS. 

Straightening:  Except  in  the  case  of  heat  treated  axles,  and  driving 
and  trailing  axles,  the  next  step  after  the  forging  is  the  straightening,  which 
is  accomplished  by  means  of  gag  presses.  From  the  cooling  beds  the 
forgings  are  carried  forward  by  over-head  cranes  to  similar  beds  in  front 
of  the  presses.  Here  each  axle  is  inspected  for  straightness,  and  those 
that  require  it  are  straightened.  Heat  treated  axles  are  straightened  after 
being  treated,  but  driving  and  trailing  axles  are  too  large  to  be  straightened 
by  the  gag  press. 

Cutting=off  and  Centering :  After  passing  the  inspection  for  straight- 
ness,  the  forgings  are  moved  forward  by  overhead  cranes  and  distributed 
to  the  cutting-off  lathes.  These  lathes  are  double  combination  cutting-off 
and  centering  machines,  and  are  designed  to  work  on  both  ends  of  the  forging 
at  the  same  time.  Upon  being  inserted  in  this  machine,  the  forging  is 
grasped  at  the  wheel  seats  by  adjustable  revolving  centering  clamps,  which 

hold  it  firmly  to  the  central  axis  of  ro- 
tation, while  two  cutting  tools,  placed 
one  at  each  end  and  adjusted  to  the 
correct  length,  are  brought  to  bear 
and  cut  off  the  excess  metal  at  the 
ends.  In  this  cutting,  a  tolerance  of 
one-eighth  inch  over  length  and  noth- 
ing under  is  permitted.  When  these 
tools  have  cut  to  within  about  one- 
half  inch  of  the  center,  they  are  run 
back  out  of  the  way,  the  pieces  of  ex- 
cess metal  are  detached  with  a  sledge, 
and  with  the  forging  still  held  by 
the  centering  clamps,  the  revolving 
centering  tools  are  brought  to  bear 
at  each  end.  These  tools  are  shaped 
FIG.  102.  Carnegie  Standard  Centering  to  cut  a  60  degree  cone-shaped  cen- 
tering hole,  five-eighths  inch  in  depth, 
one  and  one-eighth  inch  in  diameter  at  the  top,  and  with  a  clearance  hole 


512  FORGING  OF  AXLES,  SHAFTS,  ETC. 

for  points  at  the  bottom  one-half  inch  in  depth  and  three-eighths  inch  in 
diameter.  When  axles  are  ordered  to  be  smooth  forged  only,  the  operation 
of  cutting  off  and  centering  completes  the  work  done  by  the  mill.  On  such 
axles  some  excess  stock  is  necessarily  left  on  those  parts  that  are  to  be 
finished  later.  This  allowance  on  car  axles  is  generally  one-half  to  three- 
fourths  inch  over  the  finished  diameters  of  the  end  collars,  journals,  and 
dust  guards,  and  one-fourth  to  three-eighths  inch  on  wheelseats. 

Rough  Turning:  On  account  of  the  saving  that  can  be  effected  in 
handling  and  transportation  of  excess  weight,  it  is  a  decided  advantage  to 
both  the  customer  and  the  shop,  especially  to  the  latter,  that  all  rough 
turning  be  done  before  shipment  is  made,  as  it  is  only  by  rough  turning 
that  certain  flaws  can  be  detected.  Rough  turned  material  falls  into  two 
classes,  known  as  "rough  turned  on  journals  and  wheelseats,'*  and  "rough 
turned  all  over."  Axles  of  the  first  class  are  put  into  service  with  the 
center  portions  between  the  wheelseats  smooth  forged  to  size.  In  the 
case  of  axles  rough  turned  all  over,  the  center  portions  are  forged  slightly 
over  size  to  provide  for  the  metal  removed  in  turning  to  size.  In  the  case 
of  car  axles  or  other  axles  with  a  tapered  body,  this  metal  is  removed  at 
the  same  time  (or  after)  the  journals  and  wheelseats  are  rough  turned, 
in  a  special  lathe  provided  with  two  tools  controlled  by  a  former-bar  whose 
contour  is  the  same  as  the  middle  portion  of  the  axle.  In  finishing  rough 
turned  axles,  the  wheelseats  are  finish-turned  only,  while  the  dust  guards, 
journals  and  collars  are  finish-turned  and  burnished,  and  in  order  to  provide 
the  excess  metal  required  for  this  work,  these  parts  are  rough  turned  one- 
eighth  inch  over  size  on  their  diameters. 

Hollow  Boring:  Owing  to  the  many  apparent  advantages  arising 
therefrom,  the  practice  of  boring  large  axles  and  forgings  longitudinally 
through  the  center  is  being  advocated  more  and  more  strongly.  These 
advantages  are  briefly  discussed  under  the  following  headings: 

1.  Piping,  it  will  be  recalled,  was  given  as  one  of  the  causes  of  failure. 
While  the  Carnegie  Steel  Company,   by  a  generous  discard  and  close 
inspection,  aims  to  eliminate  this  defect,  yet  it  is  possible  that  some  forms 
of  piping,  notably  compound  pipes,  may  escape  both  the  discard  and  the 
inspection,  and  remain  in  the  axle  as  a  menace  to  safety.     Hollow  boring 
gives  the  inspectors  a  chance  to  detect  this  hidden  pipe. 

2.  Segregation  was  given  as  another  source  of  failure.     This  defect 
cannot  be  entirely  overcome  in  the  manufacture  of  steel,  and  inspection  is 
no  safeguard  against  it.     But  as  the  area  of  greatest  segregation  lies  about 
the  central  axis,  boring  a  hole  of  proper  size  longitudinally  through  the 
center  should,  and  does,   remove  the  greater  part  of  all   the  segregated 
material  from  the  axle. 

3.  Strength  and  Weight:     The  central  portion  of  an  axle  removed 
by  boring  is  really  a  non-essential  part  so  far  as  strength  is  concerned. 


HEAT  TREATING  FORCINGS  513 

The  transverse  strength  of  rounds  is  proportional  to  the  cubes  of  their 
diameters.  So,  for  example,  if  a  three  inch  bore  be  made  in  a  six  inch  axle, 
the  maximum  loss  in  strength  is  but  12.5%;  in  an  eight  inch  axle,  but  5.25%. 
These  figures  represent  the  loss  in  strength  provided  the  center  is  as  strong 
as  the  outer  portion,  which  condition  is  never  true  in  axles  or  similar  for  gings, 
so  that  the  actual  loss  in  strength  in  nearly  every  case  would  be  much  less 
than  these  figures  indicate.  Again,  the  axle  with  the  bored  center  may 
actually  be  stronger  than  it  would  have  been  solid,  provided  it  contained 
much  segregated  material  or  the  remnant  of  a  pipe — conditions  that  favor 
the  formation  of  internal  cracks.  Another  factor  concerns  the  relation 
between  the  loss  in  strength  and  the  loss  in  weight.  In  this  connection 
it  will  be  observed  that,  whereas  the  strength  varies  as  the  cube  of  the 
diameters,  the  weight  varies  as  the  squares.  Referring  to  the  example  just 
cited,  ,and  applying  this  law,  the  reader  will  find  that  while  in  the  case 
of  the  six  and  eight  inch  axles,  the  three  inch  boring  gives  a  loss  in  strength 
of  12.5%  and  5.25%,  respectively,  the  loss  in  weight  is  25%  for  the  first 
and  14.3%  for  the  second. 

4.  Hollow  Boring  and  Heat  Treating:  As  an  aid  in  heat  treating, 
especially  in  quenching  and  tempering,  or  toughening,  hollow  boring  is  of 
great  importance.  In  heating,  it  permits  the  heat  to  be  absorbed  much 
more  rapidly,  and  in  quenching,  the  heat  is  more  rapidly  removed  than 
in  solid  pieces,  with  the  result  that  the  structure  is  more  uniform.  Further- 
more, contraction  and  expansion  strains  are  largely  overcome,  and  shrinkage 
cavities  in  the  center  are  avoided.  The  American  Society  for  Testing 
Materials  specify  that  all  forgings  over  seven  inches  in  diameter  that  are 
to  be  quenched  shall  be  bored.  The  diameter  of  the  hole  bored  should 
equal  or  exceed  20%  of  the  largest  diameter  of  the  forging  exclusive  of 
collars  or  flanges.  Howard  Axle  Works  are  equipped  to  bore  holes  either 
two  or  three  inches  in  diameter. 

The  Heat  Treating  Plant  is  housed  in  the  same  building  with  the 
hammers  and  lathes  and  consists  of  two  furnaces  for  heating  with  the 
forgings  in  a  horizontal  position,  one  furnace  for  heating  the  material  in 
a  vertical  position,  one  water  quenching  tank,  one  oil  quenching  tank,  and 
all  the  necessary  supplemental  equipment  for  handling  and  testing  the 
material. 

The  Furnaces:  The  inside  working  space  of  the  two  furnaces  of  the 
first  type  are  each  twenty-four  feet  in  length  and  nine  feet  in  width,  and  are 
designed  to  heat  uniformly  to  a  height  of  about  four  feet  above  the  bottom. 
They  are  provided  with  removable  bottoms  of  the  car  type,  which  much 
facilitates  the  charging  and  drawing  operations.  This  bottom  is  moved 
into  and  out  of  the  furnace  by  means  of  a  toothed  rack  attached  to  the 
bottom  of  the  car  and  a  stationary  pinion  actuated  by  an  electric  motor,  the 
car  itself  resting  on  rollers  that  move  over  a  double  track.  The  doors  of  the 
furnace  are  of  the  vertically  lifting  type,  and  are  hydraulically  operated. 


514  FORGING  OF  AXLES,  SHAFTS,  ETC. 

These  features,  together  with  the  close  proximity  of  the  quenching  tanks, 
permit  the  drawing  and  quenching  of  a  charge  in  the  quickest  possible  time, 
less  than  a  minute  being  required  to  transfer  a  charge  from  the  closed  furnace 
to  either  of  the  quenching  tanks.  The  measures  taken  to  secure  uniform 
heating  are  particularly  noticeable  in  this  furnace.  The  furnace  is  of  the 
reversing  flame  type,  in  which  natural  gas  is  employed  as  fuel,  and  is  heated 
by  means  of  burners  placed  at  space  intervals  of  less  than  two  feet  along 
each  side,  thus  permitting  the  temperature  at  any  point  in  the  furnace  to 
be  controlled  to  a  nicety.  At  the  top,  the  furnace  is  closed  with  a  roof, 
arched  from  side  to  side,  while,  inside,  high  bridge  walls  extend  along  in 
front  of  the  gas  burners  to  prevent  the  flames  from  impinging  upon  the 
charge.  In  order  that  the  entire  surface  of  the  material  may  be  exposed 
to  heat  of  the  same  intensity,  the  charge  is  supported  at  a  height  of  about 
eighteen  inches  above  the  floor  of  the  car  bottom  by  two  steel  rails  that 
extend  the  entire  length  of  the  car.  These  rails  are  spaced  about  four  feet 
apart  and  are  supported  by  castings  in  the  form  of  four-legged  stools.  The 
floor  of  the  car  bottom  is  constructed  of  brick  laid  upon  a  bottom  of  steel 
plates,  and  is  of  such  thickness  as  to  give  ample  insulation  from  the  heat  of 
the  furnace.  The  bottom  is  made  to  fit  the  furnace  neatly,  and  the  escape 
of  hot  gases  from  the  heating  chamber  is  prevented  by  means  of  sand  seals. 
The  construction  of  the  furnace  for  heating  the  charge  in  a  vertical  position 
is  somewhat  like  that  of  a  soaking  pit.  It  has  a  capacity  of  about  six  axles 
and  sufficient  head  room  for  maximum  lengths  of  ten  feet.  In  operating 
this  type  of  furnace,  the  axles  are  loaded  on  a  cast  steel  rack,  which  is 
specially  designed  to  support  them  in  a  vertical  position,  and  are  lowered 
through  the  top  into  the  furnace  where  they  are  maintained  in  a  vertical 
position  throughout  the  heating  operation.  This  furnace  is  seldom  used, 
as  more  satisfactory  operating  conditions  are  obtained  by  using  the  other 
type.  For  taking  temperatures  the  Siemens  Water  pyrometer  is  used 
exclusively. 

The  Quenching  Tanks:  For  use  in  connection  with  these  heating 
furnaces,  the  plant  is  equipped  with  one  water  quenching  and  one  oil  quench- 
ing tank.  These  tanks  are  both  placed  as  near  as  possible  to  the  furnaces, 
the  water  tank  being  directly  in  front  of  one  of  the  furnaces  of  the  horizontal- 
heating  type.  This  tank,  approximately  twenty-five  feet  long,  twelve  feet 
wide  and  fourteen  feet  deep,  is  of  the  sub  level  type  and  is  constructed  of 
concrete.  When  in  use,  the  water  level  lies  about  two  feet  above  the  floor 
of  the  shop.  So,  an  ample  volume  of  water  is  supplied  for  any  charge  it  is 
practicable  to  handle,  and,  in  addition,  provision  is  made  whereby  fresh 
water  may  be  introduced  during  the  quenching  operation  at  one  corner  of 
the  tank  and  the  excess  conducted  away  at  the  diagonally  opposite  corner, 
both  inlet  and  outlet  being  located  near  the  top  of  the  tank.  Two  beams 
extending  the  full  length  of  the  tank  and  supported  about  two  feet  above 
the  bottom,  prevent  the  charge  from  resting  on  the  bottom  when  lowered 
by  the  crane,  thus  securing  more  uniform  cooling.  The  oil  quenching  tank 


HEAT  TREATING  FORGINGS  515 

is  some  sixteen  feet  in  length,  nine  feet  in  width,  and  ten  feet  in  depth, 
inside.  It  is  made  in  two  parts — an  oil  container  and  a  cooling  jacket. 
The  container  is  made  of  steel  plates  and  is  set  within  the  cooler,  which  is 
constructed  of  concrete  and  is  about  twenty  inches  longer  and  wider  than 
the  container,  so  that  a  space  of  about  ten  inches  separates  the  walls  of 
the  two  vessels.  This  space  is  kept  filled  with  cold  water,  which  serves 
to  prevent  the  temperature  of  the  oil  rising  too  high  during  quenching,  and 
to  cool  it  down  rapidly  after  each  charge. 

The  Testing  Equipment  includes  all  the  latest  devices  for  testing 
materials.  In  the  shop,  two  hollow  drill  machines  for  cutting  out  tests  are 
provided,  and  as  all  heat  treated  axles  are  given  individual  shock  tests, 
a  drop  testing  machine  for  giving  these  proof  tests  is  also  located  here. 
Two  drop  testing  machines,  adapted  for  testing  axles  in  accordance  with 
standard  specifications  are  provided.  Other  physical  tests  are  made  in  the 
physical  laboratory,  which  is  equipped  with  one  planing,  one  turning,  one 
pulling,  one  torsional,  one  bending  and  one  Brinell  machine,  and  all  the 
supplemental  appliances  for  accurate  testing. 

Advantages  of  Heat  Treating  Axles:  While  the  proper  heat  treating 
of  axles  is  accomplished  with  some  difficulty  on  account  of  their  size,  and 
is  attended  with  great  danger  if  improperly  done,  yet  with  proper  equip- 
ment, great  care  and  good  judgment,  born  of  knowledge  and  experience  on 
the  part  of  the  operator,  the  dangers  may  be  eliminated,  and  decided 
advantages  result  therefrom.  It  is  the  only  way  in  which  the  grain  struc- 
ture can  be  refined  and  made  uniform,  and  in  doing  this  all  the  evils  due 
to  variations  in  the  grain,  which  result  from  the  heating  and  working  of 
the  bloom,  are  overcome,  as  well  as  forging  strains.  But  greatest  of  all 
these  advantages  is  the  improvement  in  mechanical  properties  effected 
through  correct  heat  treatment.  It  offers  the  only  positive  means  of 
markedly  increasing  the  strength  and  wearing  properties  of  axles  without 
in  any  way  increasing  their  weight — a  thing  that  is  much  desired  under 
modern  conditions  of  traffic. 


516  CONSTITUTION  OF  STEEL 


PART  III. 

THE  CONSTITUTION    HEAT  TREATMENT  AND  COMPOSITION 

OF  STEEL. 

Introductory:  It  is  the  desire  in  this  part  of  this  little  book  to  center 
the  interest  of  the  reader  chiefly  about  the  heat  treatment  of  steel.  So 
much  progress  in  the  study  of  this  subject  has  been  made  in  recent  years 
that  many  are  inclined  to  look  upon  it  as  something  new.  That  remarkable 
changes  in  the  physical  properties  of  a  given  steel  can  be  brought  about 
through  the  agency  of  heat  alone  has  been  known  for  many  years,  but 
until  1390  the  subject  had  received  very  little  attention  from  scientists. 
Up  to  that  time  both  the  scientific  knowledge  about  the  subject  and  the 
technical  application  of  the  art  of  heat  treatment  were  very  limited,  being 
confined  for  the  most  part  to  the  making  of  tools  and  a  few  specialties. 
The  invention  of  the  automobile,  the  aeroplane,  and  other  machines,  the 
different  parts  of  which  are  required  to  be  light  and  at  the  same  time  suit- 
able for  the  usages  to  which  the  parts  are  subjected,  gave  rise  to  demands 
for  steel  of  great  strength  combined  with  various  other  specific  properties . 
These  demands  directed  the  attention  of  investigators  to  heat  treatment 
because  it  was  found  that  this  was  the  only  means  of  meeting  these  require- 
ments. Practically  all  alloy  steels  must  be  heat  treated  in  some  way,  and 
few  steels  in  their  natural  state  will  give  their  full  value  in  service,  so  that 
the  various  combinations  of  static  and  dynamic  strength  and  wearing 
qualities  required  can  be  obtained  in  their  highest  degree  only  by  adjusting 
and  correlating  both  the  chemical  composition  and  the  heat  treatment. 
Just  as  certain  chemical  components  intensify  one  set  of  properties,  and 
others  another  set,  so  the  heat  treatment  may  be  changed  to  develop 
different  qualities  in  a  similar  way.  Thus,  by  combining  the  proper  chemical 
composition  with  the  proper  heat  treatment,  there  results  a  product  posses- 
sing in  the  highest  degree  the  properties  most  desired  for  the  work  the 
steel  is  to  do.  So  it  is  evident  that  the  intelligent  application  of  heat 
treatment  to  secure  the  best  results  requires  a  thorough  knowledge,  on  the 
part  of  those  supervising  the  work,  of  the  composition  of  the  steel  and  the 
effect  of  the  various  elements  that  are  to  be  found  in  all  steels  or  that  may 
be  added  as  alloys  to  produce  the  special  steels.  Again:  Heat  treatment 
consists  in  heating  and  cooling  steel  under  conditions  that  will  produce 
the  desired  change  or  changes  in  physical  properties,  and  embraces  the 
three  processes  of  annealing,  hardening,  and  tempering,  to  which  may  be 


CONSTITUTION  OF  STEEL  517 

added  the  special  processes  known  as  ' 'process  annealing,"  "patenting," 
"case  hardening,"  etc.  The  remarkable  changes  in  properties  that  may 
be  obtained,  together  with  the  phenomena  observed  during  heating  and 
cooling,  all  connote  vital  changes  that  are  brought  about  by  the  heat 
treatment.  As  no  change  in  composition  of  the  metal  takes  place,  the 
cause  for  the  phenomena  must  be  sought  in  changes  of  arrangement  or 
condition  of  the  constituents  of  the  steel  itself.  Another  pre-requisite, 
then,  to  the  study  of  heat  treatment  is  the  study  of  the  structure  and  con- 
stituents of  steel,  a  thorough  knowledge  of  which  is  essential  to  any 
understanding  of  the  subject,  whatever.  For  this  reason,  the  study  of  heat 
treatment  should  be  prefaced  by  a  brief  summary  of  the  knowledge  con- 
cerning the  structure  and  constitution  of  steel. 

Before  beginning  this  study,  however,  the  student  should  understand 
that  part  III  of  this  book  is  intended  merely  as  an  introduction  to  the  study 
of  metallography,  heat  treatment  and  composition  of  steel.  Those  who 
desire  a  further  knowledge  of  these  valuable  and  fascinating  subjects  are 
referred  to  such  authorities  as  Albert  Sauveur1,  whose  plan  of  developing 
the  subject  is  closely  followed  in  this  study;  H.  M.  Howe2,  whose  iron 
carbon  diagrams  are  used  herein;  and  D.  K.  Bullens3,  whose  practices  in 
heat  treatment  are  frequently  referred  to. 

iSee  the  Metallography  and  Heat  Treatment  of  Iron  and  Steel,  Published  by 
Sauveur  and  Boylston,  Metallurgical  Engineers,  Cambridge,  Mass. 

2See  Iron,  Steel  and  Other  Alloys,  and  The  Metallography  of  Iron  and  Steel. 
Both  published  by  McGraw-Hill  Book  Company,  Inc.,  239  West  39th  Street,  New 
York. 

»See  Steel  and  Its  Heat  Treatment,  Published  by  John  Wiley  &  Sons,  Inc.. 
New  York  City.  _, 


518  CONSTITUENTS  OF  STEEL 


CHAPTER  I. 

THE  CONSTITUTION  AND  STRUCTURE  OF  PLAIN  STEEL. 

SECTION  I. 

STEEL  AS  AN  ALLOY  OF  IRON  AND  CARBON. 

The  Constituents  of  Steel :  Steel  is  not  a  single  element  or  compound, 
but  a  complex  artificial  product,  composed  of  many  elements  held  in  the 
solid  mass  as  a  mechanical  mixture  of  alloys  and  chemical  compounds  with 
the  element  iron.  In  ordinary  steel,  these  elements  are  iron,  carbon, 
manganese,  phosphorus,  sulphur,  silicon  and  oxygen,  with  traces  of  nitrogen, 
hydrogen  and  other  elements,  such  as  aluminum,  copper  and  arsenic.  Of 
these,  all  are  to  be  considered  as  impurities  except  carbon,  which  is  an 
essential  ingredient,  and  manganese,  or  other  elements  added  for  a  definite 
purpose.  For  the  sake  of  simplicity  and  brevity  only  pure  steel,  consisting 
of  the  two  essential  elements,  iron  and  carbon,  will  be  considered  in  this 
chapter.  Even  in  this  case  steel  is  found  to  be  an  aggregate  made  up  of 
mineral-like  components,  some  of  which  are  visible  only  with  the  aid  of 
the  microscope  after  the  surface  of  the  specimen  has  been  highly  polished 
and  etched  with  dilute  acids  or  other  corrosive  mixtures  which  affect  the 
various  constituents  in  different  ways.  To  the  structure  thus  revealed  by 
the  microscope  the  term  micro-structure  is  given,  to  distinguish  it  from  the 
macroscopic  structures,  or  those  visible  to  the  naked  eye;  and  to  the 
different  constituents  mineralogical  names  have  been  applied.  Thus,  in 
pure  steels  which  have  cooled  slowly  from  a  high  temperature,  three  dis- 
tinct constituents  are  recognized.  They  are  called  ferrite,  pearlite,  and 
cementite,  and  in  the  different  steels  will  vary  in  amount  according  to  the 
carbon  content. 

Ferrite  is  the  term  applied  to  pure  iron,  i.  e.,  carbonless  iron,  when 
it  is  considered  as  a  microscopical  constituent  of  steel.  It  is  soft,  ductile 
and  relatively  weak,  having  a  tensile  strength  of  about  40,000  pounds 
and  an  elongation  of  40  per  cent,  in  two  inches.  It  has  practically  no 
hardening  power,  a  high  electric  conductivity,  and  can  be  magnetized. 
It  appears  white  in  color  after  being  etched  with  dilute  alcoholic  nitric  or 
picric  acids.  It  is  best  seen  in  steels  containing  .10%  to  .30%  carbon, 
'  when  it  appears  as  a  network  surrounding  bodies  of  pearlite,  another  con- 
stituent of  steel  to  be  described  shortly. 

Cementite:  As  already  stated,  iron  and  carbon  are  the  essential 
elements  in  steel,  and  of  these  carbon  may  be  termed  the  controlling  element. 
When  steels  are  cooled  slowly  from  high  temperatures,  from  the  fusion 


THE  CONSTITUTION  OF  STEEL 


519 


1.  Photomicrograph 
showing  a  grain  of  pear- 
lite  surrounded  wi  th  free 
ferrite  as  a  net  work. 
Specimen  taken  from  an- 
nsaled  steel  containing 
carbon  .48  per  cent,  and 
manganese  .54  per  cent. 
Magnified  750  diameters 

Etched  first  in  5% 
alcoholic  picric  acid  for 
eight  seconds,  then  in 
5%  alcoholic  nitric  acid 
for  five  seconds.  White 
area  represents  ferrite. 
On  account  of  a  too  rapid 
rate  of  cooling,  the  pearl- 
lite  is  not  fully  devel- 
oped. Compare  with 
Figs.  48  and  113. 


2.  Photomicrograph 
of  a  specimen  of  steel 
containing  carbon  to  the 
extent  of  1.50  percent. 
The  excess  cementite  is 
here  seen  in  the  form  of 
spines,  or  needles. 

Magnified  100  diam- 
eters. Etched  for  eight 
seconds  in  five  percent, 
alcoholic  picric  acid  and 
for  two  seconds  in  five 
per  cent,  nitric  acid, 
making  the  free  cement- 
ite, which  stands  in 
relief,  brilliant  white 
in  color. 


Co, 


520  CONSTITUTION  OF  STEEL 

point,  for  example,  all  the  carbon  is  found  combined  with  a  definite  amount 
of  iron  in  the  form  of  a  carbide  of  iron  corresponding  to  the  chemical  formula 
FesC.  This  compound  consists  of  carbon,  6.67  per  cent,  and  iron,  93.33 
per  cent.,  and  it  is  known  micrographically  as  cementite.  Any  excess  iron 
is  practically  free  of  carbon  at  atmospheric  temperatures  and  remains  as 
ferrite  in  steels  that  have  cooled  slowly.  Little  is  known  about  the 
properties  of  cementite  except  that  it  is  very  hard  and  brittle.  Indeed, 
it  is  the  hardest  component  of  steel,  and  will  scratch  glass  and  feldspar 
but  not  quartz.  It  is  about  two-thirds  as  magnetic  as  pure  iron  under  an 
exciting  current.  After  polishing  the  surface  of  steel,  it  stands  in  relief, 
and  is  brilliant  white  after  etching  with  dilute  hydrochloric  or  picric  acids. 
It  occurs  free  in  ordinary  steels  of  more  than  .90%  carbon,  in  which  it 
appears  as  a  network  or  as  spines  and  needles.  It  takes  its  name  from 
cement  steel,  made  by  the  cementation  process,  which  contains  a  great 
deal  of  this  carbide,  FesC. 

Pearlite:  One  of  the  most  remarkable  characteristics  of  cementite 
and  ferrite  is  their  power  of  forming  the  conglomerate  known  as  pearlite. 
During  the  process  of  slowly  cooling  steel  from  higher  temperatures,  say 
above  1000°  C.,  it  has  been  found  that  the  cementite  and  ferrite  always 
form,  at  about  700°  C.,  a  mechanical  mixture  made  up  of  definite  amounts 
of  each  and  in  the  proportion  of  about  seven  parts  ferrite  to  one  part 
cementite,  so  that  the  resultant  conglomerate  will  contain  approximately 
.90%  carbon.  This  constituent  then  consists  of  interstratified  layers  or  bands 
of  ferrite  and  cementite,  and  is  called  pearlite  on  account  of  its  resemblance 
to  mother  of  pearl.  While  pearlite  commonly  occurs  in  slowly  cooled  steels 
in  the  lamellar  formation,  composed  of  alternate  layers  of  ferrite  and 
cementite,  it  may  under  different  rates  of  cooling  and  dependent  on  the 
relative  amounts  of  ferrite  and  cementite  present,  exist  in  other  formations, 
or  phases,  of  which  some  authorities  have  recognized  at  least  four,  making 
in  all  five  modifications.  Normal  pearlite  has  a  maximum  tensile  strength 
of  about  105,000  pounds,  and  an  elongation  of  about  10%  in  two  inches.  It  is 
regarded  as  a  separate  and  distinct  constituent  of  steel  because  it  forms 
distinct  masses  or  "grains,"  always  contains  this  definite  percentage  of 
carbon  and  is  always  formed  at  a  definite  temperature,  or  a  range  of 
temperatures,  to  be  more  exact. 

Manner  of  Freezing  of  Solutions  and  Alloys:  In  order  to  clarify 
the  explanation  of  the  formation  of  pearlite,  it  is  necessary  to  digress  to 
the  extent  of  explaining  some  of  the  freezing  laws  of  solutions.  A  study 
of  the  freezing  of  solutions  has  shown  that  they  fall  into  two  classes,  namely, 
those  in  which  the  ingredients  in  solution  in  the  liquid  state  remain  in 
solution  in  the  solid  state  and  those  in  which  the  state  of  solution  is  not 
maintained  in  the  solid  state,  that  is,  those  in  which  the  ingredients  separate 
on  freezing. 

An  Example  of  the  First  Class  of  Solutions :  One  of  the  best  examples 
of  the  first  kind  of  solution  is  a  mixture  of  gold  and  silver.  If  quantities  of 


FREEZING  OF  ALLOYS 


521 


these  two  metals  be  placed  in  a  vessel  and  heated  until  they  melt,  a  homo- 
geneous mixture,  or  a  liquid  solution,  results;  and  if  this  mixture  be  allowed 
to  cool  to  the  solid  state,  it  is  still  homogeneous,  that  is,  it  is  a  solid  solution. 
A  study  of  many  mixtures  in  which  the  proportions  of  gold  to  silver  are  varied 
shows  that  freezing  begins  at  a  different  temperature  for  each  mixture. 
Pure  gold  freezes  at  1062°  C.  and  pure  silver  at  961°  C.,  and  the  freezing 
points  of  the  mixtures  occur  between  these  two  points.  Unlike  the  pure  metals, 
however,  these  mixtures  do  not  solidify  completely  at  a  constant  temperature, 
but  their  freezing  is  prolonged  through  ranges  of  temperature.  These  facts, 
definitely  determined  by  experiment,  may  be  represented  by  a  diagram,  or 
curve,  such  as  the  following,  in  which  the  ordinates  represent  temperatures 
and  the  abscissae  the  percentage  of  gold  or  silver  or  both. 


Temperatures—  Degrees  Centigrade 

Liquid 

Solution 

Freezing  Point 
of  Pure  Gold. 

Freezing  Point 
ot  Pure  Silver. 

; 

Cl 

"^ 

~**1 

^^ 

^ 

s' 

"f^^ 

^!^___ 

^^^ 

Solid 

Solution 

%Gold    100                80                  60                  4o                 20                    0 
%bilver     o                  20                  40                  60                 80                100 
FIG.  104.     Diagram  of  the  Freezing  of  Liquid  Gold-Silver  Alloys. 

To  illustrate  further,  suppose  sixty  ounces  of  gold  be  mixed  with  forty 
of  silver,  and  the  whole  heated  to  a  temperature  of  1090°  C.  The  locus  of 
this  point  would  be  at  "1"  in  the  region  of  the  liquid  state.  It  now  this 
molten  mass  be  allowed  to  cool,  crystals,  each  of  which  contains  60%  gold 
and  40%  silver,  begin  to  separate  out  at  "f,"  about  1041°  C.,  and  continue 
to  do  so  until  the  point  "s,"  about  990°  C.,  where  the  last  of  the  liquid 
freezes,  is  reached.  No  further  change  takes  place  as  the  cooling  proceeds, 
and  the  solid  mass  is  found  to  be  homogeneous  and  of  the  same  composition 
as  the  liquid  solution.  Any  other  mixture  of  these  two  metals  would  give  a 
like  result,  except  with  respect  to  the  freezing  points,  and  the  solid  crystals 
would  be  found  to  be  made  up  of  gold  and  silver  in  the  same  proportion 
as  they  were  in  the  liquid  state. 

Example  of  the  Second  Class  of  Solutions— Salt  and  Water:    It  is 

a  well  known  fact  that  a  solution  of  common  table  salt  freezes  at  a  lower 
temperature  than  pure  water.  This  lowering  of  the  freezing  point,  or  rather 
the  temperature  at  which  freezing  begins,  varies  with  the  proportion  of 


522 


THE  CONSTITUTION  OF  STEEL 


salt  to  water  until  this  proportion  has  reached  the  definite  limit  of  23.5%, 
when  any  further  addition  of  salt  causes  the  point  at  which  freezing  begins  to 
rise.  This  lowest  temperature,  at  which  the  solution  containing  23. 5%  of  salt 
freezes,  is  — 22°  C.  These  facts  are  represented  by  the  diagram  of  Fig.  105. 

Two  or  three  examples 
will  suffice  to  explain  the 
freezing  of  solutions  contain- 
ing varying  amounts  of  salt, 
and  any  other  points  about 
the  diagram  that  may  not  be 
clear.  Thus,  suppose  a  solu- 
tion containing  10%  of  salt  is 
at  a  temperature  indicated  by 
"1".  Although  water  freezes 
at  0°  C.,  the  temperature  of 
this  solution  must  fall  to  the 
40point  "f,"  about  —10°  C., 

FIG.  105.     Diagram  Representing  the  Freezing   before  freezing  begins.  Here, 
of  Solutions  of  Salt;  in  Water.  unlike  the  solution  of  gold 

and  silver,  crystals  of  pure  water  begin  to  separate  from  the  solution.  The 
separation  of  these  crystals  has  the  effect  of  increasing  the  percentage  of  salt 
in  the  mother  liquor,  so  that  the  separation  of  the  water  crystals  continues 
only  so  long  as  the  temperature  is  being  lowered.  Furthermore,  if  the  rate 
of  cooling  has  been  uniform  down  to  the  point  "f,"  a  marked  retardation 
takes  place  here,  because  the  heat  of  fusion  of  the  water  must  be  removed 
before  ice  can  be  formed.  With  the  removal  of  this  heat,  however,  and  that 
necess  ary  to  lower  the  temperature  of  the  remaining  solution,  the  separa- 
tion of  ice  crystals  continues,  causing  a  concentration  of  salt  in  the  mother 
liquor  that  bears  a  definite  relation  to  the  temperature  aa  indicated  by  the 
line  M  O.  Finally,  when  a  temperature  of  — 22°  C.  is  reached,  the  mother 
liquor,  which  now  contains  23.5%  of  salt,  freezes  as  rapidly  as  the  heat  of 
fusion  is  abstracted.  When  all  this  liquor  has  solidified,  the  temperature 
of  the  solid  mass  will  continue  to  fall  uniformly  in  a  manner  similar  to  that 
before  freezing  began. 

If  instead  of  the  weak  solution,  a  strong  brine  containing  more  than 
23.5%  of  salt  is  substituted  in  the  experiment  just  described,  it  is  found 
that,  just  as  ice  separated  along  the  line  M  O.,  salt  crystals  separate  out 
along  the  line  N  O  until  the  temperature  — 22°  C.  is  reached  and  the  mother 
liquor  contains  23.5%  of  salt.  This  liquor  then  freezes  as  described  before. 
When  these  facts  were  first  observed,  it  was  thought  that  the  mother  liquor 
that  is  the  last  to  freeze  was  a  hydrate  of  sodium  chloride  of  the  formula 
NaCl.lOH^O.  and  was  called,  therefore,  the  cryohydrate,  cold  hydrate, 
meaning  a  hydrate  that  could  exist  in  the  solid  state  only  at  low  temper- 
atures. It  has  since  been  shown  that  these  cryohydrates  are  not  chemical 
compounds,  though  they  have  a  definite  composition,  but  are  mechanical 
mixtures  made  up  of  crystallized  salt  and  ice  in  intimate  contact. 


FREEZING  OF  ALLOYS 


523 


Lead  and  Tin  Solutions  as  Another  Example  of  the  Second  Kind 
of  Freezing:  Many  of  the  fused  alloys  exhibit  the  same  phenomena  in 
freezing  that  saline  solutions  do,  showing  that  their  constituent  metals 
form  a  solution  when  in  the  liquid  state  but  that  they  are  insoluble  in  one 
another  in  the  solid  state.  As  an  example  of  such  an  alloy,  that  of  lead 
and  tin  is  most  convenient  for  study.  To  cite  a  specific  example,  let  a 
mixture  composed  of  30%  tin  and  70%  lead  be  heated  to  a  temperature 
of  350°  C.  As  this  temperature  is  above  the  fusion  points  of  both  lead  and 
tin,  which  melt  at  327°  C.  and  232°  C.,  respectively,  it  is  sufficiently  high 
to  insure  that  the  mixture  will  be  completely  fused.  Now,  as  this  solution 
cools  down,  no  crystallization  takes  place  until  a  temperature  of  about 
270°  C.  is  reached,  when  crystals  of  lead  begin  to  separate  out,  making 
the  remaining  solution  poorer  in  lead  but  richer  in  tin  in  the  same  way  as 
the  ratio  of  salt  to  water  became  greater  during  the  freezing  of  the  weak 
saline  solution.  Likewise,  as  in  the  case  of  the  salt  solution,  the  separation 
of  the  lead  causes  a  retardation  of  the  rate  of  cooling,  showing  that  heat  is 
evolved  thereby;  and  the  freezing  point  of  the  mother  liquor  becomes  lower, 
so  that  no  further  separation  of  lead  takes  place  until  more  heat  is 
abstracted.  If  the  cooling  be  continued,  however,  the  separation  of  the 
lead  will  also  continue,  and  if  proper  measures  be  taken,  a  number  of  loci 
may  be  obtained  of  the  cooling  curves  for  alloys  of  different  composition, 
which,  when  plotted,  give  the  curve  M  O  as  represented  in  the  diagram 
of  Fig.  106. 


Freezing  point 
of  pure  lead. 


Freezing  point 
of  pure  tin. 


Fia.  106.     Diagram  Illustrating  the  Freezing  of  Lead-Tin  Alloys. 


When  the  cooling  and  the  accompanying  separation  of  lead  has  reached 
the  point  O.,  corresponding  to  a  temperature  of  180°  C.  and  31%  of  lead, 
or  69%  tin,  in  the  mother  liquor,  the  whole  mass  becomes  solid,  forming 
a  banded  structure  composed  of  minute  crystals  of  lead  and  tin  and  cor- 
responding to  the  cryohydrate  of  salt  and  water,  but  called,  in  the  case 
of  alloys,  eutectic  alloy,  which  signifies  easily  melted  alloy.  To  the  right 
of  the  point  O,  tin  separates  along  N  O  like  lead  along  M  O.  This  manner 


524 


CONSTITUTION  OF  STEEL 


of  freezing,  where  one  metal  separates  alone,  is  known  as  selective  freezing 
to  distinguish  it  from  the  kind  of  freezing  illustrated  by  the  gold-silver 
alloys,  which,  since  both  metals  separate  together,  is  known  as  non=selec- 
tive  freezing. 

The  Iron=Carbon  Eutectic:  Coming  now  to  a  consideration  of  the 
iron  carbon  alloys,  the  student  finds  that  the  freezing  of  alloys  of  these 
two  elements  presents  phenomena  that  are  like  those  of  both  the  gold- 
silver  and  the  lead-tin  alloys.  The  freezing  of  these  alloys  is  represented 
by  the  following  diagram,  from  which  it  is  seen  that  the  carbon  content 

IRON-CARBON  SYSTEM 


%  CARBON 


FIG.  107.    Diagram  Demonstrating  the  Freezing  and  Cooling  of  Iron  Carbon  Alloys. 
After  H.  M.  Howe. 

of  the  eutectic  alloy  is  about  4.30%.  Therefore,  when  alloys  that  contain 
more  than  this  amount  of  carbon  are  cooled  from  temperatures  above  the 
line  M  O  N,  carbon  in  the  form  of  graphite  separates  along  N  O  until 
the  point  O  is  reached,  when  the  eutectic  solidifies.  Naturally,  the  reader 
would  expect  a  similar  separation  of  iron  along  the  line  M  O;  but  it  is 
here  that  the  freezing  of  the  solution  produces  phenomena  similar  to  the 
freezing  of  gold-silver  alloys,  for  it  is  found  that,  instead  of  pure  iron  separat- 


FREEZING  OF  IRON-CARBON  ALLOYS  525 


ing,  a  definite  mixture,  or  alloy,  containing  approximately  2.0%  carbon  and 
called  primary  austenite,  separates  from  all  mixtures  in  which  the  carbon 
content  is  two  per  cent,  or  more.  By  drawing  in  the  vertical  line  A  D, 
corresponding  to  about  2.0%  carbon,  this  diagram  is  divided  into  two 
parts.  The  part  to  the  right  of  A  D  shows  the  freezing  of  the  iron  carbon 
alloys  to  be  like  that  of  the  lead-tin  alloys,  that  is,  selective,  while  that 
part  to  the  left  of  A  D  shows  that  the  freezing  of  all  iron-carbon  alloys 
whose  carbon  content  is  less  than  2.0%  is  non-selective  and  analogous  to 
the  freezing  of  the  gold-silver  alloy.  For  example,  suppose  an  iron-carbon 
alloy  containing  1.0%  carbon  to  be  at  a  temperature  of  1500°  C.  It  is  in  the 
liquid  state  and  represents  a  homogeneous  mixture  of  iron  and  carbon,  or 
a  solution  of  carbon  in  iron.  If  now  this  solution  is  allowed  to  cool,  crys- 
tallization will  begin  when  the  temperature  indicated  by  the  corresponding 
point  "f"  on  the  line  M  O  is  reached,  and  will  continue  up  to  the  point 
"s"  on  the  line  M  P,  when  the  solidification  will  have  been  completed. 
Each  crystal  that  separates  contains  1.0%  C.,  and  when  the  point  "s"  is 
passed,  the  mass  represents  a  solid  solution  with  a  carbon  content  of  1.0%. 
This  solid  solution  is  also  known  as  primary  austenite.  Because  of  this 
difference  in  the  freezing  of  the  iron  carbon  alloys  between  those  contain- 
ing more  than  2.0%  carbon  and  those  containing  less  than  2.0%  carbon, 
the  carbon  content  of  2.0%  may  be  considered  as  the  dividing  line  between 
steel  and  pig  iron;  consequently,  this  study  is  concerned  mainly  in  the 
changes  that  occur  in  alloys  whose  composition  is  represented  by  the  region 
in  the  diagram  that  lies  to  the  left  of  the  line  A  D. 

Formation  of  Pearlite  and  the  Eutectoid :  By  studying  the  cooling 
of  the  primary  austenite  through  the  region  below  M  P,  it  is  found  that  this 
solid  solution  of  carbon  in  iron  undergoes  changes  similar  in  character  to  those 
presented  by  the  freezing  of  the  liquid  solution.  These  changes  are  repre- 
sented by  a  secondary  set  of  curves  as  shown  in  the  part  of  the  diagram  to  the 
left  of  AD.  This  diagram  indicates  that  a  substance  corresponding  to  the 
eutectic  of  liquid  alloys  is  formed  and  that  it  contains  about  .90%  carbon, 
but  since  it  is  formed  from  a  solid  solution,  it  is  called  the  eutectoid,  a 
term  that  means  "something  of  the  nature  of  an  eutectic."  It  will  be 
observed  that  as  the  primary  austenite  is  cooled  from  M  P,  the  line  of 
complete  solidification,  that  any  alloy  with  a  carbon  content  greater  than 
.90%  precipitates  iron  carbide,  Fe3C,  along  the  line  P  O',  whereas  those, 
in  which  the  carbon  content  is  less  than  .90%,  throw  out  of  solution  pure 
iron  or  ferrite  along  M'  O'  until  the  eutectoid  composition  is  reached. 
The  unchanged  alloy,  to  which  the  term  mother  metal  may  be  applied, 
then  undergoes  a  change  wherein  the  precipitation  of  both  the  iron  and 
the  iron  carbide,  FesC,  is  completed  simultaneously,  with  the  result  that  the 
eutectoid  thus  formed  consists  of  interstratified  layers  of  ferrite  and  cement- 
ite,  commonly  called  pearlite,  as  previously  explained.  Hence,  the  term 
eutectoid  is  often  applied  to  pearlite,  when  it  is  desired  to  indicate  the 
manner  of  its  formation  and  its  structural  characteristics.  Since  the  metal 


526  CONSTITUTION  OF  STEEL 

is  in  the  solid  form  during  these  changes,  it  having  reached  its  freezing 
point  500°  to  800°  C.  above  the  temperature  of  formation  for  pearlite,  the 
cause  for  these  changes  cannot  be  ascribed  to  a  change  in  state.  While 
many  theories  have  been  advanced  to  explain  this  and  other  facts  the 
most  satisfactory  explanation  is  that  iron  exists  in  at  least  two,  possibly 
three,  allotropic  forms.  Thus,  below  a  temperature  of  690°  C.  it  exists  in 
a  form  designated  as  the  alpha  form,  in  which  it  has  no  power  of  dissolving 
carbon  or  the  carbide,  cementite,  whereas  above  this  temperature  it  can 
hold  this  constituent  in  solid  solution.  At  these  higher  temperatures  it  is 
designated  as  the  gamma  form,  and  the  solid  solution  of  carbon,  or  carbide, 
in  iron,  is,  micrographically,  called  austenite.  Furthermore,  the  change 
from  austenite  to  pearlite  is  not  instantaneous,  and,  as  will  be  explained 
later,  several  transition  products  may  intervene,  the  complete  series  being 
austenite,  martensite,  troostite,  sorbite  and  pearlite.  From  what  has  been 
said,  it  is  evident  that  a  steel  that  contains  .90%  carbon  will,  if  cooled 
slowly  from  any  point  above  the  critical  temperature  for  its  formation, 
consist  entirely  of  pearlite.  Such  steels  are  designated  as  eutectoid  steels, 
while  those  that  contain  less  than  .90%  carbon  are  termed  hypo=eutectoid 
steels,  and  those  in  which  the  carbon  content  exceeds  .90%  are  called 
hyper=eutectoid  steels.  Other  phenomena  which  accompany  the  cooling 
of  the  primary  austenite  will  be  described  in  the  next  section. 

Structural  Composition  of  Slowly  Cooled  Steel:  All  steels  that 
have  been  cooled  slowly  from  a  temperature  above  that  for  the  formation 
of  pearlite  will  contain  it  as  a  constituent.  Thus,  in  the  case  of  hypo- 
eutectoid  steels,  all  the  carbon  present  will  be  found  as  pearlitic  cementite, 
the  amount  of  pearlite  being  controlled  by  the  amount  of  carbon  present. 
Any  ferrite  above  that  required  by  the  cementite  in  the  formation  of  pearlite 
will  be  rejected  as  free,  or  excess,  ferrite.  In  such  steels,  this  excess  ferrite 
is  in  the  form  of  a  network  surrounding  small  masses  of  the  pearlite.  In 
the  case  of  hyper-eutectoid  steels,  the  amount  of  pearlite  is  again  controlled 
by  the  carbon,  but  in  an  indirect  way.  As  all  the  carbon  combines  with 
iron  to  forAi  cementite,  only  a  limited  portion  of  ferrite  remains  for  the 
formation  of  pearlite.  As  this  ferrite  is  not  sufficient  to  interstratify  with 
all  of  the  cementite,  an  excess  of  the  latter  remains.  Like  the  rejected 
ferrite,  this  excess  cementite  will  also  appear  as  a  network  about  the  masses 
of  pearlite.  Thus,  from  the  carbon  content  of  a  slowly  cooled  steel  it  is 
possible  to  determine  accurately  the  structural  composition,  or  from  the 
relative  proportions  of  pearlite  and  ferrite  or  cementite  as  revealed  by 
the  microscope,  the  practiced  metallographer  can  determine  the  approxi- 
mate carbon  content. 

Effect  of  These  Constituents  Upon  the  Physical  Properties:    The 

data  on  the  physical  properties  of  these  constituents  enables  the  student 
to  understand  the  remarkable  effect  of  carbon  upon  the  physical  properties 
of  ordinary  steel.  In  brief,  the  facts  in  their  relation  to  the  static  strength 
of  slowly  cooled  steel  are  as  follows:  1.  Each  constituent  has  the  power 


THERMAL  CRITICAL  POINTS 


527 


to  impart  to  the  steel  its  own  properties  in  proportion  to  the  extent  of  its 
presence.  2.  Ferrite  has  the  minimum  tensile  strength  but  maximum 
ductility.  3.  Pearlite  has  maximum  tensile  strength  with  low  ductility. 
4.  Cementite  has  great  hardness  and  brittleness  with  very  little  strength. 
The  effect  of  these  constituents  upon  the  properties  of  steel  are  plainly 
shown  in  the  accompanying  diagram. 


100 


120,000 
100,000 


-     40     S       80,000 

P. 


GO 


I    30   I 


60,000 


40   I    20   I       40,000 


20          10  P       20,000 


1.00         1.20          1.40 


%CarbonO  .20  40  .60  .« 

FIG.  108.     Diagram   Showing   the   Approximate    Influence   of    Carbon   Upon  the 
Strength  and  Ductility  of  Steel  and  its  Relation  to  the  Pearlite  Content. 


SECTION   II. 

THERMAL  CRITICAL  POINTS   OF  STEEL. 

Nature  of  Critical  Points  or  Ranges  of  Steel:  The  structural  and 
other  changes  in  steel  just  described  take  place  at  temperatures  known  as 
the  thermal  critical  points,  or  critical  ranges,  because  they  are  points  in  the 
cooling  or  heating  of  the  metal  that  are  marked  by  the  spontaneous  evolution 
or  absorption  of  heat.  The  most  marked  of  these  is  the  range  commonly 
called  the  point  of  recalescence  and  point  of  decalescence. 

Thermal  Critical  Point  for  Eutectoid  Steel:  For  example,  suppose 
a  piece  of  steel,  containing  .90%  carbon  and  at  a  temperature  of  1000°  C., 
be  allowed  to  cool  slowly.  If,  now,  the  rate  of  cooling  be  carefully  ascer- 
tained by  means  of  a  pyrometer,  it  will  be  found  that  the  cooling  proceeds 
at  first  at  a  uniformly  retarded  rate,  thus  following  the  law  for  all  cooling 
bodies.  But  when  a  temperature  of  about  700°  C.  is  reached,  the  uniformly 
retarded  cooling  is  momentarily  arrested.  A  pyrometer  will  not  only  fail 
to  record  any  further  decrease  in  temperature,  but  in  most  cases,  when 
the  conditions  are  favorable,  will  show  that  the  temperature  of  the  cooling 


528  CONSTITUTION  OF  STEEL 

mass  actually  rises.  These  facts  show  that  heat  is  spontaneously  generated 
within  the  metallic  body  in  amount  sufficient  to  balance,  or  more  than 
balance,  that  lost  through  radiation  and  conduction.  If  the  experiment  is 
performed  in  the  dark,  the  steel  will  be  observed  to  glow  at  this  point  due 
to  the  heat  evolved,  and  so  the  term  recalescence  has  been  applied  to  it. 
Investigation  has  shown  that  the  amount  of  heat  given  off  in  this  case  is 
about  16  cal.  per  gram  of  pearlite. 

Thermal  Critical  Points  for  Pure  Iron:  If  instead  of  the  eutectoid 
steel,  a  piece  of  the  purest  iron  obtainable  be  substituted  in  the  experiment 
just  described,  the  cooling  of  this  pure  iron  is  found  to  be  very  unlike  that 
for  the  eutectoid  steel.  Thus,  the  metal  will  be  found  to  cool  at  a  uniformly 
retarded  rate  till  a  temperature  of  900°  C.  is  reached,  when  a  marked 
increase  in  retardation  occurs,  showing  that  heat  is  being  evolved,  but 
insufficient  to  cause  an  actual  rise  in  temperature  of  the  body  of  metal, 
i.  e.,  a  recalescence.  The  cooling  will  then  resume  a  normal  rate  until 
the  temperature  of  about  760°  is  reached,  when  a  second  evolution  of  heat 
takes  place,  but  not  so  pronounced  as  in  the  first  instance.  The  metal  then 
cools  normally  to  atmospheric  temperatures.  Thus,  in  pure  iron  there  are 
two  evolutions  of  heat,  i.  e.,  two  critical  points,  both  of  which  take  place 
at  a  higher  temperature  than  that  noted  for  eutectoid  steel  and  without 
actual  rise  in  temperature.  Carbonless  iron,  therefore,  has  no  point  of 
recalescence. 

Thermal  Critical  Points  of  Low  Carbon  Steel:  If  the  same  experi- 
ment be  now  performed  with  a  steel  containing  even  a  small  per  cent,  of 
carbon,  say  .10%,  the  influence  of  this  element  is  found  to  be  very  marked. 
Three  thermal  retardations  will  be  detected,  the  first,  the  most  marked, 
at  about  850°  C.,  the  second  near  760°  C.,  and  the  third  at  the  point  of 
recalescence,  near  700°  C.  The  last  two  are  very  faint. 

Thermal  Critical  Points  of  Medium  Carbon  Steel:  If  the  experi- 
ment with  low  carbon  steels  be  repeated  with  specimens  containing  higher 
and  higher  percentages  of  carbon,  the  upper  critical  points  observed  in  the 
preceding  experiment  on  .10%  carbon  steel  and  carbonless  iron  will  be  found 
to  be  lower  and  lower  as  the  percentage  of  carbon  is  increased,  until,  finally, 
the  determination  of  the  rate  of  cooling  of  a  steel  containing  .35%  or  .40% 
carbon  reveals  only  two  critical  points,  the  upper  one  at  about  740°  C. 
and  the  other  at  the  point  of  recalescence,  700°  C.  This  fact  means  that 
the  carbon  has  caused  the  two  upper  points  observed  in  pure  iron  and  low 
carbon  steels  to  merge  into  one  critical  point.  Furthermore,  experiments 
on  steel  containing  a  higher  per  cent,  of  carbon  than  .40  show  that  the  two 
lower  critical  points  remaining  also  apparently  merge  into  one  on  steels 
containing  .60%  carbon  and  over.  Theoretically,  this  apparent  merging 
should  not  take  place  till  the  steel  is  composed  entirely  of  pearlite,  that 
is,  when  it  has  the  eutectoid  composition  and  contains  .85%  to  .90%  carbon. 
The  early  merging  is  attributed  to  the  difficulty  of  distinguishing  by  experi- 
ment two  critical  points  so  close  together. 


THERMAL  CRITICAL  POINTS 


529 


The  Carbon=Iron  Diagram  for  Steels  and  Methods  of  Notation: 

These  critical  points  or  ranges  are  indicated  graphically  in  the  accom- 
panying diagram  of  Fig.  109,  which  is  seen  to  be  the  same  a»  that  used  in 
explaining  the  formation  of  pearlite.  This  diagram  refers  to  the  critical 


1050 


1000  ._ 


960 


%  Carbon 

%Cementite         0. 
%  Pearlite  0. 

%Free  Ferrite  100. 
%FreeCementiteO. 


1.80 

24.  27. 

87. —  83.+ 

0.  0. 

13.  17. 

Fia.  109.     Diagram  Showing  Position  of  the  Critical  Ranges  and  the  Relation  of  the 
Carbon  Content  to  that  of  Pearlite  and  Ferrite  and  Cementite. 


points  on  cooling,  which  occur  at  temperatures  somewhat  lower  than  on 
heating.  All  these  critical  ranges  are  denoted  by  the  letter  "A,"  followed 
by  either  the  small  letter  r,  an  abbreviation  for  the  French  word 
"refroidissement,"  cooling,  or  the  small  letter  c,  which  stands  for 
"chauffage,"  signifying  heating.  These  signs,  Ar  and  Ac,  are  further 
modified  by  the  numerals  1,  2,  3,  indicating  the  point  of  recalescence,  the 
second,  and  the  third  points  encountered  on  heating,  respectively.  Thus, 
Acl  means  the  first  critical  point  passed  upon  heating  the  steel,  and  so  on. 


530  CONSTITUTION  OF  STEEL 

The  Position  of  the  Critical  Ranges  is  affected  in  many  ways.  Atten- 
tion has  already  been  called  to  the  difference  between  the  ranges  on  heating 
and  cooling.  '  In  commercially  pure  carbon  steels,  Ar±  almost  invariably 
takes  place  between  690°  C.  and  720°  C.  and  Ac±  20  to  40  degrees  higher. 
It  has  been  well  established  that  this  lagging  of  the  point  on  cooling  and 
the  point  on  heating  behind  the  true  point  is  a  case  of  hysteresis,  often 
observed  in  physical  phenomena.  Evidence  of  the  correctness  of  this 
explanation  is  found  in  the  fact  that  the  slower  the  heating  and  cooling 
the  nearer  the  two  points  approach  each  other.  The  speed  of  cooling  or 
heating,  then,  is  the  first  factor  affecting  the  position  of  these  points.  A 
second  factor  influencing  the  positions  of  Arj  is  found  in  the  temperature 
to  which  the  steel  is  heated  before  cooling  begins.  The  higher  this  tem- 
perature and  the  longer  it  is  held  at  the  high  temperature  the  lower  the 
position  of  ArA  will  be;  but  this  change  in  position  of  the  critical  point  is 
not  pronounced  and  takes  place  very  gradually  and  slowly.  A  third  factor 
is  that  of  chemical  composition.  In  general  the  presence  of  impurities  in 
the  steel  have  a  tendency  to  lower  the  position  of  Ac  and  Ar,  and  in  some 
cases  this  tendency  is  very  decided.  Thus,  manganese  lowers  the  position 
of  Ar  some  25°  C.  to  50°  C.  for  each  per  cent,  of  that  element  present  in  the 
steel.  Nickel  and  copper  also  lower  the  Ar  range.  In  the  case  of  nickel 
and  manganese  the  lowering  is  so  pronounced  that  in  a  steel  containing 
13%  Mn.  and  25%  Ni.  no  retardation  is  observed  in  cooling  from  a  high 
to  atmospheric  temperature,  but  appears  on  cooling  in  liquid  air,  which 
indicates  that  the  Art  point  has  been  lowered  in  this  steel  to  below  the 
temperature  of  the  air.  In  the  ordinary  steel  of  commercial  quality,  the 
impurities  are  present  in  so  small  amounts  that  they  can  cause  little  vari- 
ation in  the  position  of  the  critical  points. 

• 

Changes  at  the  Thermal  Critical  Points:  Besides  the  rise  in  tem- 
perature or  retardation  of  cooling  already  explained,  careful  investigation 
has  shown  that  other  important  changes  take  place  in  steels  in  passing 
through  these  ranges.  For  convenience  these  changes  and  their  effects 
are  summed  up  as  follows: — 

I.  Changes  at  A.^:  The  point  AS,  as  already  shown,  applies  to 
carbonless  iron  and  steels  containing  less  than  .35%  carbon.  The  passing 
of  such  steels  through  this  point  is  accompanied  by  the  following  phenomena: 
1.  On  cooling,  the  metal,  which  above  Ar$  was  contracting,  undergoes  a 
sudden  and  marked  expansion  in  volume  on  passing  through  Ar3.  In  linear 
units  the  expansion  amounts  to  about  one  one-thousandth  of  its  length.  This 
dilation  is  then  immediately  followed  by  normal  contraction,  again.  2.  Above 
A3  the  metal  has  an  electrical  resistance  about  ten  times  greater  than  its 
resistance  at  ordinary  temperatures.  At  A.TS  a  sudden  drop  in  this  resist- 
ance takes  place,  after  which  the  decrease  proceeds  slowly  at  a  uniform 
rate  until  atmospheric  temperature  is  reached.  3.  A  change  in  crystalline 


THERMAL  CRITICAL  POINTS  531 

form  of  iron  takes  place  at  AS.  Below  this  point  iron  crystallizes  in  the 
cubic  form,  but  this  form  changes  on  passing  Acs  to  that  of  the  octahedra. 
4.  The  tensile  strength  of  iron  at  the  AS  point  has  been  shown  to  undergo 
a  distinct  discontinuity,  (see  page  337).  5.  The  dissolving  power  of  iron  for 
carbon  is  one  of  the  most  important  changes  which  the  properties  of  the  metal 
undergo  in  passing  the  Acs  point.  From  what  has  been  said  in  the  preceding 
section  it  may  be  surmised  that  below  this  point,  or  at  least  as  long  as 
the  iron  is  in  the  alpha  form,  it  has  no  power  of  dissolving  carbon,  but 
it  gains  this  power  immediately  the  Ac3  point  has  been  passed.  6.  An 
abrupt  structural  change  accompanies  the  passage  of  all  low  carbon  steels 
through  this  range.  It  is  on  reaching  this  point  that  the  free  ferrite  begins 
to  be  set  free,  which  continues  till  the  residual  austenite  is  of  the  proper 
composition  for  the  formation  of  pearlite. 

II.  Changes  at  A2:    As  indicated  in  the  iron-carbon   diagram,   A2 
occurs  as  a  separate  point  only  in  carbonless  iron  and  in  steels  containing 
less  than  .35%  carbon.    Just  as  the  retardation  on  cooling  was  found  to 
be  faint  at  this  point,  so  the  changes  in  properties  are  not  so  numerous 
nor  so  marked  as  at  A$.     Thus,  there  is  no  dilation,  no  structural  change, 
no  change  in  crystalline  form,  and  probably  no  change  in  the  dissolving 
power  of  iron  for  carbon  on  passing  through  the  range  A2.     But  the  following 
three  changes  in  properties  on  passing  A2  are  to  be  specially  noted.     The 
magnetic   properties   undergo   a  marked  change  on  passing  A2.     Above 
this  point  steel  is  non-magnetic,  or  para  magnetic,  but  in  passing  through 
Ar2  it  suddenly  becomes  strongly  magnetic,  and  gradually  becomes  more 
so  as  the  cooling  continues,  finally  gaining  its  full  magnetism  at  a  tem- 
perature of  about  500°  C.     A  distinct  discontinuity  in  both  the  tensile 
strength  and  specific  heat  of  iron  at  the  A2  point  has  been  shown  to  take 
place. 

4 

III.  Changes  at  A3,2,  which  point  results  from  themergingof  Aaand  A2, 
are  tfye  same  as  those  occurring  in  low  carbon  steels  in  passing  through  A$. 

IV.  Changes  at  Ait    As  previously  explained,  the  point  A!  occurs 
in  all  steels  containing  from  a  mere  trace  to  .90  per  cent,  carbon.     It  cor- 
responds to  the  transformation  of  residual  austenite  into  pearlite.     At  this 
point  the  following  sudden  changes  in  properties  are  noted:    1.    A  dilatation 
takes  place  which  increases  with  the  carbon  content,  reaching  a  maximum 
with  .85%  carbon.    2.     Increased  magnetism  takes  place  for  all  steels  on 
cooling  through  this  point.    3.    A  marked  decrease  in  electrical  resistance 
is  also  noted  on  cooling  through  this  range.    4.     Below  this  point  iron 
loses  entirely  its  power  to  dissolve  carbon.    5.  The  important  changes  from 
austenite  to  pearlite  have  already  been  shown  to  take  place  at  AI,  but  it 
is  well  to  emphasize  their  significance  here,  for  these  changes  give  the  key 
to  the  rational  treatment  of  steel.     The  spontaneous  transformation  of 
austenite  of  eutectoid  composition  into  pearlite,  that  is,  a  solid  solution 


532  CONSTITUTION  OF  STEEL 


into  an  aggregate  of  the  eutectoid,  makes  possible  the  refining  of  steel  by 
heat  treatment,  because  on  being  heated  through  its  critical  range,  the 
steel  is  changed  from  a  coarse  aggregate  to  a  fine,  almost  amorphous,  solid 
solution.  This  fact  is  also  the  secret  of  hardening  steel,  as  will  be  shown 
later. 

Causes  of  the  Thermal  Critical  Points  in  Steel:  In  seeking  a  cause 
for  the  existence  of  the  thermal  critical  points  in  steel,  all  the  phenomena 
exhibited  must  be  considered.  Starting  first,  then,  with  the  thermal 
changes  noted  in  the  experiments  previously  described,  it  is  well  to  note 
that  there  are  but  three  well  known  causes  of  spontaneous  evolution  of 
heat  in  cooling  bodies  and  of  similar  absorptions  of  heat  on  heating  them. 
Briefly,  these  causes  are  (1.)  the  formation  or  decomposition  of  chemical 
compounds;  (2.)  changes  of  state,  whether  by  solution  or  by  the  agency 
of  heat;  and  (3.)  allotropic  or  polymorphic  transformations,  which  are 
always  accompanied  by  either  an  absorption  or  evolution  of  heat  when 
the  substance  of  the  body  passes  from  one  allotropic  condition  to  another. 
As  to  the  upper  points,  AS  and  A2,  it  has  been  shown  that  at  these  points 
even  carbonless  iron  either  absorbs  or  evolves  heat,  depending  upon  whether 
the  metal  is  being  heated  or  cooled  while  passing  through  the  ranges.  The 
fact  that  the  iron  is  pure,  nothing  being  present  with  which  it  could  combine, 
and  the  fact  that  it  is  in- the  solid  state  throughout  the  experiment,  preclude 
the  possibility  of  either  a  chemical  change  or  a  change  of  state  having 
taken  place  to  cause  the  thermal  changes  indicated.  Only  the  explanation 
founded  on  the  basis  of  allotropy,  therefore,  remains.  According  to  the 
two  thermal  changes  that  occur,  then,  pure  iron  or  ferrite  exists  in  at  least 
three  allotropic  forms.  Below  the  point  A2  it  is  called  alpha  iron,  between 
A2  and  AS  it  is  known  as  beta  iron,  while  above  AS  it  is  said  to  be  in  the 
gamma  form.  While  it  is  not  desirable  to  undertake  a  discussion  of  this 
theory  here,  it  may  be  pointed  out  that  all  the  changes  in  properties  pre- 
viously mentioned  as  accompanying  these  critical  points  are  but  additional 
evidence  of  the  correctness  of  this  view.  Since  the  influence  of  carbon  is 
to  delay  the  separation  of  ferrite,  it  may  be  that  beta  iron  is  not  formed 
on  cooling  steels  containing  .35%  carbon  or  more,  for  since  the  temperature 
of  the  point  Arg-2  in  such  steels  is  below  that  for  the  formation  of  beta 
iron,  it  is  probable  that  just  as  iodine  passes  directly  from  the  solid  to  the 
gaseous  state  by  sublimation,  or  as  amorphous  sulphur  at  atmospheric 
temperatures  passes  to  rhombic  sulphur,  so  gamma  iron  passes  directly 
to  the  alpha  form.  The  fact  that  the  point  AI  does  not  occur  in  carbonless 
iron  and  only  faintly  in  low  carbon  irons,  while  with  increase  of  the  carbon 
it  increases  in  intensity,  is  evidence  that  this  point  is  due  solely  to  the 
presence  of  carbon.  Unlike  the  points  AS  and  A2,  which  are  due  to  allo- 
tropic forms  of  iron,  AI  is  not  due  to  any  change  in  the  carbon  itself,  but 
merely  to  the  formation  of  pearlite,  which  implies  the  crystallization  or 
falling  out  of  solution  of  cementite,  FesC,  coupled  with  the  complete 
change  of  the  ferrite  from  the  gamma  to  the  alpha  state  as  well.  Above 


CRYSTALLINE  STRUCTURE  533 


AI,  the  FesC,  being  in  solution  with  the  gamma  iron  and  thoroughly  diffused, 
has  the  power  of  imparting  its  own  properties,  hardness  and  brittleness, 
to  the  steel  in  a  more  pronounced  way  than  when  in  the  segregated  form 
in  which  it  occurs  below  AI.  Hence,  formerly  due  to  the  theories  then 
advanced  to  explain  the  hardening  effect  of  carbon,  the  term  hardening 
carbon  was  applied  to  it  above  AI,  while  below  AI  it  was  called  cement 
carbon. 

SECTION   III. 

THE   CRYSTALLINE    STRUCTURE   OF   STEEL. 

Crystals  and  Grains:  That  the  crystalline  structure  of  steel  exerts 
a  deep  influence  upon  its  strength  and  ductility  is  a  well  known  fact.  Since 
this  structure  lends  itself  to  refinement  through  proper  heat  treatment,  a 
clear  understanding  of  all  the  laws  governing  the  crystallization  of  steel 
is  essential  to  the  art  of  heat  treating  steel.  When  steel,  like  many  other 
substances,  passes  from  the  liquid  to  the  solid  state,  the  process  of  solidi- 
fication is  accompanied  by  crystallization,  that  is,  the  molecules  of  the 
various  ingredients  arrange  themselves  so  as  to  form  small  bodies  having 
regular  geometrical  outlines.  Each  of  such  bodies  constitutes  a  crystal. 
In  the  case  of  iron  in  the  gamma  form  the  crystals  are  octahedra,  or  small 
eight  sided  bodies,  but  when  the  iron  is  in  the  alpha  condition  these  crystals 
are  cubic  in  form.  Crystals  have  the  remarkable  pr6perty,  called  cleavage, 
of  breaking  most  easily  along  certain  planes  usually  parallel  to  the  faces  of 
the  crystal.  Hence,  these  planes  of  easy  rupture  are  called  cleavage  nrfanes. 
The  direction  of  the  cleavage  planes  constitutes  the  orientation  nrf  the 
crystal.  Perfect  crystals,  called  idiomorphic  crystals,  are  formed  only 
when  the  conditions  are  favorable.  Thus,  with  high  fluidity,  absence  of 
foreign  particles,  slow  rate  of  cooling,  and  with  the  liquid  at  rest  and 
undisturbed,  perfect  crystals  of  large  size  may  form.  Because  of  the  unfavor- 
able conditions  that  usually  prevail  in  its  manufacture,  the  crystallization 
of  steel  results  in  the  formation  of  imperfect  crystals  with  irregular  forms 
and  smaller  in  size  than  perfect  crystals.  These  imperfect  crystals  are, 
scientifically,  designated  as  allotrimorphic  crystals,  but  the  metallurgist 
speaks  of  them  simply  as  grains. 

Crystallization  of  Steel  :  As  an  aid  to  understanding  the  crystalliza- 
tion of  steel  it  will,  perhaps,  be  best  to  follow  the  crystallographic  history 
of  a  steel  casting  that  is  allowed  to  cool  slowly  from  the  casting  temper- 
ature to  atmospheric  temperature.  For  the  present,  let  this  steel  be  of 
any  carbon  content.  During  the  solidification  period,  what  has  been 
termed  the  primary  crystallization  takes*  place,  which  consists  in  the 
formation  of  macroscopic  tree-like  bodies  of  austenite  called  dendrites. 
Each  of  these  dendrites  is  composed  of  small  octahedra,  which  is  repre- 
sentative of  the  crystallographic  form  for  austenite.  Of  these,  Stead  writes: 
"The  fine  fir-tree  crystallites,  containing  probably  a  fraction  of  the  amount 


534  CONSTITUTION  OF  STEEL 

of  the  carbon  in  the  liquid  steel,  grow  steadily  forward  from  the  cold  surface 
of  the  containing  moulds.  The  crystallites  develop  branches  in  three 
directions  corresponding  to  the  axes  of  the  cube,  and  these  branches  throw 
out  similar  branches  themselves..  Eventually  parts  of  the  most  fusible 
portions  are  trapped  between  the  branches  and  are  the  last  to  solidify. 
When  there  is  much  phosphorus  or  some  sulphur  in  the  metal,  they  are 
always  present  together  with  an  excess  of  the  carbon  in  the  last  residue 
of  metal  that  remains  liquid,  and  although  in  cooling  down,  after  the  liquid 
has  solidified,  the  excess  carbon  diffuses  out  of  it  into  the  purer  part,  the 
sulphides  and  phosphides  do  not,  but  remain  fixed,  and  can  generally  be 
detected  in  the  solid  metal." 

After  the  solidification  is  complete  a  crystalline  transformation,  called 
granulation,  sets  in  and  continues  until  the  critical  range  is  reached,  where 
all  steels  are  found  to  be  made  up  of  grains,  each  grain  having  its  own 
orientation  and  being  made  up  of  small  octahedra  of  crystalline  matter. 
The  size  of  these  grains  varies  with  the  rate  of  cooling,  just  as  the  rate  of 
cooling  affects  the  size  of  crystal  in  any  metal.  In  passing  through  the 
critical  range  the  structural  changes  are  affected  by  the  amount  of  carbon 
present,  and  for  this  reason  it  is  best  to  consider  the  three  grades  of 
eutectoid,  hypo-eutectoid,  and  hyper-eutectoid  steels  separately  from  this 
point  onward. 

Crystallization  of  Eutectoid  Steels:  In  the  eutectoid  steels  the 
growth  of  the  grains  will  continue  down  to  the  point  Ari,  where  the  metal 
will  b I  made  up  of  grains  of  austenite  containing  ferrite  and  cementite  in 
proper  proportions  to  form  pearlite.  Therefore,  in  passing  through  the 
critical  point,  Ar±,  each  austenite  grain  changes  bodily  into  a  grain  of 
pearlite.  Hence,  the  coarse  austenitic  structure  acquired  by  cooling  from 
a  high  temperature  gives  rise  to  a  correspondingly  coarse  pearlite  structure. 

Crystallization  of  Hypo-Eutectoid  Steel:  As  an  example  of  the 
genesis  of  the  crystalline  structure  of  steels  of  hypo-eutectoid  composition 
let  a  steel  containing  .60%  carbon,  corresponding  to  72%  pearlite  and  28% 
free  ferrite,  be  selected.  In  such  a  steel  the  granulation  will  proceed  till  the 
upper  critical  point  Ar3-2  is  reached,  where  free  ferrite  begins  to  be  rejected 
and  continues  till  the  point  Arj  is  reached,  when  the  residual  austenite, 
being  of  the  proper  eutectoid  composition,  passes  into  pearlite  as  described 
for  eutectoid  steels.  An  important  point  to  be  noted  here  is  the  fact  that 
this  setting  free  of  the  excess  ferrite  is  brought  about  through  the  rejection 
of  ferrite  in  excess  of  the  eutectoid  composition  by  each  individual  grain 
of  austenite,  either  to  its  boundaries  or  between  its  cleavage  planes. 
When  each  grain  of  austenite  becomes  a  grain  of  pearlite,  the  ferrite  pre- 
viously rejected  still  remains  as  an  envelope,  thus  forming  the  net-work 
mentioned  under  "Ferrite."  Therefore,  the  structure  of  cast  hypo-eutectoid 
steel  is  very  coarse,  for  the  following  three  reasons:  1.  The  slow  and 


CRYSTALLINE  STRUCTURE  535 

undisturbed  cooling  promotes  the  formation  of  large  austenite  grains  and 
hence,  later,  of  large  pearlite  grains.  2.  The  slow  cooling  between  the 
upper  and  lower  critical  points  favors  the  rejection  of  a  maximum  amount 
of  free  ferrite,  which  rejection  makes  for  coarseness  of  structure.  3.  The 
slow  cooling  from  the  upper  critical  point  to  atmospheric  temperature 
promotes  the  crystallization  of  excess  ferrite  into  large  grains,  especially 
when  this  excess  is  large  in  amount,  i.  e.,  in  very  low  carbon  steel.  Because 
of  its  coarse  structure,  cast  hypo-eutectoid  steel  is  less  tenacious  and  less 
ductile  than  forged,  rolled  or  properly  annealed  steel  of  similar  composition. 

Crystallization  of  Hyper=Eutectoid  Steels:  In  the  case  of  hyper- 
eutectoid  steels,  the  granulation  proceeds  to  the  point  Acm,  a  temperature 
that  is  indicated  by  the  line  Acm  in  Fig.  109,  where  excess  cementite  is 
liberated — like  the  excess  ferrite  in  hypo-eutectoid  steels.  This  excess 
cementite  is  rejected  either  to  the  boundaries  of  the  austenite  grains  or 
between  their  cleavage  planes,  where,  after  the  transformation  of  eutectoid 
austenite  into  pearlite,  it  remains  to  form  a  network  about  the  grains  of 
the  latter. 

The  Effect  of  Work  on  Grain  Size:  The  effect  of  work  on  the 
mechanical  properties  of  steel  has  been  discussed  in  the  second  part  of  this 
book.  It  remains  to  be  pointed  out  here  that  the  greatest  benefits  of  working 
as  the  steel  cools  to  Art  are  due  to  a  refinement  in  the  grain  size.  The  ex- 
planation for  this  refinement  is  found  in  the  fact  that,  as  each  grain  is 
distorted  by  the  application  of  mechanical  pressure,  it  endeavors  to  resume 
its  original  form,  but  being  hindered  in  this  by  the  rigidity  of  the  mass, 
it  breaks  up  into  a  number  of  smaller  grains  possessing  the  characteristic 
form.  If  the  steel  be  worked  at  temperatures  below  Ar±,  cold  working, 
no  refinement  rof  grain  takes  place,  as  the  great  rigidity  of  the  metal  or 
its  lack  of  molecular  energy  prevents  any  readjustment  of  the  grains  at  all. 
Hence,  cold  worked  steel  will  show  a  pronounced  distortion  of  grain. 

Crystalline  Changes  on  Heating  Steel:  Since  the  preceding  dis- 
cussions have  been  concerned  mainly  with  steel  under  conditions  of  cooling, 
it  may  be  profitable  to  review  these  changes  from  the  standpoint  of  heating. 
Starting,  then,  with  a  low  carbon  steel,  containing,  say,  .20%  carbon,  it 
will  be  found  that,  under  normal  conditions  of  manufacture  and  in  its  natural 
state,  this  steel  consists  of  approximately  24%  pearlite  and  76%  free  alpha 
ferrite,  the  pearlite  existing  in  small  grains  surrounded  by  the  ferrite  as  a 
network.  Upon  heating  through  the  point  Aci,  the  pearlite  changes  into 
austenite,  the  iron  of  which  is  in  the  gamma  form;  but  the  free  ferrite  is 
still  in  the  alpha  form.  As  the  heating  continues  throughout  the  zone 
bounded  by  Ac±  and  Ac2  the  austenite  thus  formed  begins  to  absorb  the 
free  ferrite.  Upon  passing  through  the  Ac2  range  the  remaining  alpha 
ferrite  changes  into  beta  ferrite;  and  the  steel  as  a  whole  will  be  found  to 
be  hard  and  non-magnetic.  As  the  heating  progresses  through  the  second 
zone,  lying  between  Ac2  and  Acs,  the  beta  ferrite,  which  is  only  a  remnant 


536  CONSTITUTION  OF  STEEL 

of  the  original  alpha  ferrite,  is  gradually  absorbed,  so  that  as  the  range 
Acs  is  passed  the  whole  of  the  steel  passes  into  the  condition  of  austenite, 
or  a  solution  of  iron  carbide  in  gamma  iron.  In  a  similar  manner  the  changes 
in  the  constituents  of  steels  of  any  carbon  content  up  to  eutectoid  steel 
might  be  explained.  In  each  case,  however,  it  is  to  be  noted  that  the 
temperature  at  which  the  transformations  are  completed  falls  as  the  carbon 
content  is  increased,  being  at  its  lowest  when  the  eutectoid  ratio  has  been 
reached.  In  the  case  of  hyper-eutectoid  steels,  the  free  cementite  is 
absorbed  in  a  manner  analogous  to  the  absorption  of  free  ferrite  in  hypo- 
eutectoid  steels.  But  the  final  solution  of  the  cementite  takes  place  at 
a  temperature  range  indicated  by  the  line  Acm,  and  much  more  slowly 
than  ferrite.  This  latter  point,  being  a  matter  of  great  practical  importance, 
should  be  kept  in  mind. 

Crystalline  Refinement  on  Heating:  Besides  these  structural 
changes  brought  about  by  heating  the  steel  through  the  various  critical 
ranges,  there  still  remains  a  matter  of  extreme  importance  to  be  explained. 
This  matter  refers  to  the  crystalline,  or  grain,  refinement  observed  when 
a  steel  is  heated  through  these  ranges.  Again  assuming  that  the  steel  is 
in  a  normal  condition  after  manufacture  in  the  usual  manner,  no  change 
on  heating  is  observed  to  take  place  in  the  grain  structure  until  the  tem- 
perature has  reached  that  of  the  lower  critical  range,  Ac^.  At  this  tem- 
perature, which  marks  the  point  where  the  original  pearlite  grains  are 
transformed  into  austenite  grains,  the  maximum  refinement,  that  is,  the 
smallest  grain  size  possible,  occurs.  This  refinement  is  to  be  expected 
from  the  conditions  of  the  formation  of  the  austenite.  Since  the  conditions 
favorable  for  the  formation  of  large  grains  require  slow  cooling  from  a  high 
temperature,  the  formation  of  the  austenite  at  this  low  temperature  permits 
no  growth  of  the  grain  structure  at  all.  Hence,  it  is  found  to  be  almost 
amorphous  in  respect  to  its  grain  structure.  But  it  is  to  be  especially 
noted  that,  as  the  temperature  is  raised  above  this  critical  range,  grain 
growth  begins,  which  fact  results  in  a  gradual  coarsening  of  the  grain  of 
the  austenite  as  the  temperature  is  progressively  raised  above  this  range. 
It  is  also  to  be  noted  that  this  increase  in  grain  size  not  only  varies  with 
the  temperature  above  the  critical  range,  but  also  with  the  length  of  time 
at  which  the  steel  is  maintained  at  the  high  temperature.  In  eutectoid 
steels,  then,  complete  and  maximum  refinement  of  the  grain  takes  place 
immediately  the  point  Ac±  is  passed.  But  if  the  steel  contains  free  ferrite 
or  free  cementite,  that  is,  if  it  is  of  hypo-eutectoid  or  hyper-eutectoid 
grade,  then  the  steel  as  a  whole  is  not  refined  on  passing  Ac^  because  the 
excess  ferrite  or  cementite  remains  unaltered.  In  all  cases  it  is  only  when 
all  the  constituents  of  the  steel  have  passed  into  the  state  of  a  solid  solution, 
or  austenite,  that  complete  refinement  can  be  obtained.  To  bring  about 
such  a  condition,  it  is  necessary  to  heat  such  steels  to  a  temperature  a  little 
above  that  of  their  upper  critical  ranges  as  indicated  on  the  iron  carbon 
diagram,  on  account  of  hysteresis  previously  discussed. 


CRYSTALLINE  STRUCTURE 


537 


1.  Heated  to  about  1300°  C. 
and  quenched  in  water. 

2.  Heated  considerably  above 
the  critical  range    and  quenched 
in  water. 

3.  Heated  to  just  above    the 
critical   range    and    quenched    in 
water. 

4.  Heated  to  just  below  the 
critical    range    and    quenched    in 
water. 


5.'    Steel  as  forged  and  cooled 
in  air  to  atmospheric  temperatures. 


FIG.  110.     Natural  Size  Photographs  Showing  Effect  of  Heat  Upon  Grain  Size  of  a 
Rolled  and  Forged  Steel,  Carbon  .75%  (Metcalf's  Experiment). 


1.     Steel  as   cast  and  cooled 
naturally. 


2.     Heated    to    927°    C. 
quenched    in    water. 


and 


FIG.  111.     Natural  Size  Photographs  Showing  Effect  of  Heat  Upon  the  Grain  Size  of 
Cast  Steel.     Specimens,  left  to  right,  contain,  .25%  Carbon  and  .36%  Carbon. 

Practical  Importance  of  Grain  Structure:  The  proper  refinement 
of  grain  structure  is  of  great  practical  importance.  An  illustration  of  the 
way  in  which  the  facts  pointed  out  above  in  connection  with  the  effects 
of  mechanical  work  and  heat  upon  the  grain  structure  of  steel  may  be  prac- 


538  CONSTITUTION  OF  STEEL 

tically  applied  is  furnished  by  the  welding  of  steel.  If  two  steel  bars  are 
welded  together  by  scarfing  the  ends  slightly  and  hammering  lightly  over 
the  weld  only,  as  is  the  practice  of  most  blacksmiths  in  welding  iron  bars, 
it  is  found  that,  while  the  weld  itself  is  strong,  the  welded  bar  will  be  weak 
on  each  side  of  the  weld.  A  bending  test  applied  to  such  a  weld  generally 
causes  the  bar  to  break  a  short  distance  from  the  weld,  which  fact  is 
responsible  for  the  assertion,  often  made  by  some  blacksmiths,  that  the 
weld  is  stronger  than  the  bar.  A  careful  examination  of  the  whole  bar, 
however,  will  usually  show  that  the  regions  on  each  side  of  the  weld  are 
the  weakest  points  in  the  entire  bar.  Evidently  this  weakness  has  been 
developed  in  the  process  of  welding.  The  high  temperature  required  in 
welding  increases  the  grain  size  of  the  ends  to  be  welded  for  a  considerable 
distance  along  the  bars.  The  subsequent  hammering  refines  this  large 
grain  in  the  weld  itself,  but  not  in  the  areas  on  each  side  of  it.  By  changing 
the  manner  of  welding  somewhat,  the  structure, of  the  welded  bar  can  be 
made  almost  uniform  throughout,  and  these  defective  areas  will  not  appear. 
This  result  can  be  accomplished  by  making  the  weld  in  the  following 
manner,  which  is  the  usual  practice  in  welding  steel:  The  two  ends  to  be 
welded  are  first  heated  to  a  moderate  forging  temperature  for  a  distance 
of  several  inches  back,  the  exact  distance  depending  upon  the  size  of  the 
bar;  these  ends  are  then  stove  up,  or  upset,  that  is,  the  heated  regions 
are  shortened  and  thickened  by  hammering  directly  against  the  ends. 
Next,  the  ends  are  scarfed,  but  instead  of  a  short,  blunt  scarf  sometimes 
used,  a  well  beveled  scarf  should  be  made.  The  scarfed  ends  are  then 
heated  to  a  welding  temperature;  a  flux  of  common  river  sand  or  a  reliable 
commercial  welding  compound  is  applied;  the  weld  is  made  as  usual;  and 
the  thickened  portion  of  the  bar  is  forged  down  to  a  size  conforming  to  the 
remainder.  This  forging  refines  the  grain  which  had  previously  been  made 
coarse  by  the  heating,  and  restores  the  uniform  structure  of  the  bar.  If 
the  bars  have  been  stove  up  right  in  the  beginning,  the  form  of  the  weld 
will  be  such  as  to  require  the  greatest  amount  of  forging  where  the  grain 
is  the  largest  and  will  decrease  to  none  where  the  steel  was  heated  only  to 
the  critical  range. 


Summary  of  Chapter  I.  The  conditions  and  properties  of  the  iron 
carbon  alloys  and  their  constituents  may  be  summed  up  about  as  follows: 
Above  the  critical  ranges,  the  iron  is  in  the  gamma  form,  and  the  carbon 
is  dissolved,  thus  imparting  to  the  alloy,  when  the  carbon  is  present  to  the 
amount  of  about  .30%,  the  power  of  hardening;  the  alloys  are  non-magnetic 
and  crystallize  on  cooling  slowly,  but  mechanical  working  prevents  the  growth 
of  the  crystals  and  reduces  their  size.  Below  the  critical  range,  the  metal 
represents  an  aggregate  of  ferrite  and  cementite,  FesC,  and  it  possesses  little 
heardning  power.  Here  the  iron  is  in  the  alpha  form,  the  alloys  are  magnetic, 
no  crystallization  takes  place,  and  mechanical  working  distorts  the  grain 
structure. 


THE  TREATING  OF  STEEL  539 


CHAPTER  II. 

HEAT  TREATING  THEORY  AND  PRACTICE. 

Introduction:  While  considerable  time  has  now  been  spent  in  a 
discussion  of  subjects  that  may  appear  to  be  purely  theoretical  in  nature 
and  of  little  practical  value,  yet  this  course  is  justified,  because  the  principles 
explained  form  the  basis  of  all  heat  treating  processes,  and  a  clear  under- 
standing of  them  is  therefore  essential.  The  practical  application  of  these 
principles  will  now  be  considered  under  the  following  headings,  correspond- 
ing to  the  three  chief  processes  of  heat  treatment  as  explained  in  the 
beginning. 

SECTION   I. 

ANNEALING. 

The  Annealing  Operation  consists  in  (1)  heating  the  steel  to  some 
predetermined  temperature,  (2)  keeping  the  temperature  constant  at  the 
predetermined  point  for  a  given  length  of  time,  and  (3)  cooling  the  steel 
according  to  some  predetermined  course  to  atmospheric  temperature.  To 
accomplish  the  desired  result  in  the  given  steel  to  be  treated  requires  that 
all  three  of  these  steps  in  the  annealing  operation  be  very  carefully  planned 
and  as  carefully  carried  out,  for  the  success  of  the  operation  depends  entirely 
upon  the  proper  correlation  of  the  rate  of  heating,  the  temperature  to  which 
the  steel  is  heated,  the  time  it  is  kept  at  the  annealing  temperature  and 
the  fate  of  cooling. 

Purpose  of  Annealing:  Evidently,  then,  the  annealing  operation  will 
be  modified  to  suit  the  end  sought.  In  general,  the  purpose  of  annealing 
may  involve  any  one  or  all  of  the  following  aims:  1.  To  soften  the  steel 
in  order  that  it  may  meet  certain  physical  requirements  or  be  more  easily 
machined.  2.  To  relieve  internal  stresses  and  strains  induced  by  forging, 
rolling,  or  drawing,  or  by  a  non-uniform  contraction  in  cooling.  3.  To 
remove  coarseness  of  grain  and  thus  secure  a  more  desirable  combination 
of  strength,  elasticity  and  ductility  for  resisting  the  stresses  to  which  it  is 
to  be  subjected  in  service.  The  treatment  is  generally  applied  (1)  to  hot 
forged  steel  objects,  because  their  grain  structure  is  often  more  or  less 
heterogeneous  and,  owing  to  high  finishing  temperature,  relatively  coarse; 
(2)  to  cold  worked  steel,  such  as  sheets  and  cold  drawn  wire,  which  often 
must  be  annealed  in  order  to  increase  or  restore  its  ductility;  and  (3)  to  steel 
castings,  which  usually  have  so  coarse  a  grain  structure  as  to  be  very 
deficient  both  in  strength  and  ductility. 


540  THE  TREATING  OF  STEEL 


True  Annealing  and  "Process"  or  "Works"  Annealing:  To  accom- 
plish the  results  sought  as  expressed  above  in  aims  (1)  and  (2),  it  is  not 
always  necessary  to  heat  the  steel  to  the  critical  range.  Thus,  in  the 
"process"  or  "works"  annealing  employed  in  wire  drawing,  it  is  only 
necessary  to  heat  the  steel,  which  contains  less  than  .10%  carbon,  to  about 
550°  C.  in  order  to  relieve  the  strained  condition  of  the  ferrite  and  restore 
the  ductility.  The  same  is  also  true  in  the  case  of  the  "white  annealing" 
of  cold  rolled  sheets.  It  is  to  be  noted,  however,  that  this  treatment  does 
not  develop  the  maximum  softness,  because  the  pearlite  is  not  affected.  But 
as  this  constituent  is  present  in  so  small  amounts,  its  influence  is  scarcely 
evident.  This  method  is  also  sometimes  applied  to  tool  steels  in  order  to 
soften  them  for  machining.  All  true  or  full  annealing,  however,  requires 
that  the  steel  be  heated  to  a  temperature  above  that  of  its  upper  critical 
range,  and  it  is  to  this  true  annealing  the  following  discussion  is  to  be 
confined. 

Heating  for  True  Annealing:  The  first  step  in  the  annealing 
operation  is  to  heat  the  steel  past  its  critical  range,  for  in  so  doing  the 
previous  structure  is  completely  obliterated  and  a  new  one,  nearly  amor- 
phous, is  born.  As  has  been  previously  explained,  this  important  change 
is  due  to  the  passage  of  the  steel  structure  from  the  state  of  an  aggregate 
of  ferrite  and  cementite  to  a  homogeneous  solid  solution.  Should  the  steel 
remain  below  the  critical  range,  no  structural  change  takes  place,  if  the 
case  of  strain  relief  noted  above  in  cold  worked  steel  be  excepted.  The 
coarsening  effect  upon  the  grain  size  of  steel,  brought  about  by  heating 
above  this  range,  has  already  been  explained.  The  proper  temperature, 
then,  for  true  annealing  is  one  but  slightly  above  the  critical  range  of  the 
steel,  and  this  temperature  must  be  maintained  uniformly  as  near  the 
range  as  possible  during  the  time  the  steel  remains  at  the  annealing 
temperature. 

The  following  ranges  of  temperatures  are  recommended  by  the  committee 
on  heat  treatment  of  the  American  Society  for  Testing  Materials. 

TABLE  59.     Annealing  Temperatures  as  Recommended  by  the 
American  Society  for  Testing  Materials. 

Range  of  Carbon  Content.  Range  of  Annealing  Temperature. 

Less  than  0.12  per  cent.  875  to  925  degrees  C. 

0.12  to  0.25  per  cent.  840  to  870  degrees  C. 

0.30  to  0.49  per  cent.  815  to  840  degrees  C. 

0.50  to  1.00  per  cent.  790  to  815  degrees  C. 

These  temperatures  are  shown  diagramatically  in  the  accompanying 
figure,  together  with  recommendations  by  other  authorities. 


ANNEALING 


541 


975 


850 


925 


.7 


.8 


.1  .2  .3  .4  .5  .6 

Per  Cent.  Carbon 

Fia.  112.     Annealing  (and  Hardening)  Ranges  Showing  Approximately  the  Temper- 
atures Recommended  by  Different  Authorities. 


Legend. 

Sauveur  (for  treating  f orgings) . 

American  Society  for  Testing  Materials. 

Bullens  (for  annealing  and  hardening). 

Stead's  Lower  Curve  (for  refining  and  hardening). 
Stead's  Upper  Curve  (for  annealing  and  normalizing). 


542  THE  TREATING  OF  STEEL 

In  large  bodies,  the  central  portion  will  lag  in  temperature  behind  the 
exterior,  hence  such  objects  should  be  heated  very  slowly,  for  very  evident 
reasons.  The  practice  of  raising  the  temperature  of  the  furnace  beyond 
the  proper  annealing. temperature  in  order  to  drive  the  heat  to  the  interior 
of  the  piece  is  a  great  mistake,  for  then  the  temperature  of  the  exterior 
may  be  carried  beyond  the  proper  point  with  consequent  evil  results 
attending. 

Importance  of  Time  in  Heating  for  Annealing:  The  time  the  object 
should  remain  at  the  annealing  temperature  is  governed  largely  by  its  size. 
Evidently,  it  .should  be  maintained  at  this  temperature  until  it  has  become 
uniformly  heated  throughout.  The  committee  quoted  above  recommends 
that  an  exposure  of  one  hour  is  sufficient  for  pieces  twelve  inches  thick.  In 
practice,  however,  it  is  often  necessary  to  keep  the  object  at  the  annealing 
temperature  for  a  much  longer  period  than  that  indicated  by  the  committee 
or  that  which  theoretically  would  appear  sufficient.  This  is  especially 
true  with  plain  steel  in  cases  where  the  mechanical  work  upon  the  steel  has 
been  severe,  or  where  the  steel  has  been  improperly  heated  in  working,  and 
in  certain  of  the  alloy  steels.  It  has  been  shown  by  Bullens1  "that  the 
greater  the  internal  stress  upon  the  steel  the  greater  is  the  amount  of  lag, 
or  final  release,  of  this  stress  behind  the  actual  change  of  constituents. 
That  is,  even  though  a  totally  new  structure  may  be  formed  by  the  anneal- 
ing temperature,  there  remains  for  a  considerable  length  of  time  a  tendency 
of  the  new  structure  to  return,  upon  slow  cooling,  to  the  stressed  condition  of 
the  original,  even  though  the  constituents  themselves  may  be  those  born 
at  the  new  temperature.  It  is  important,  therefore,  if  a  soft  steel 
free  from  all  internal  stresses  and  strains  is  desired,  that  a  sufficient  length 
of  time  be  allowed  for  the  permanent  elimination  of  these  stresses  and 
strains,  before  cooling."  To  accomplish  this  result  a  period  of  time 
extending  over  several  hours,  or  even  days,  may  be  required. 

Cooling:  Having,  thus,  by  proper  rate  of  heating  and  length  of  time 
of  heating,  obtained  the  steel  in  a  state  favorable  to  maximum  refinement, 
the  next  step  is  to  cool  it  properly.  As  variations  in  the  rate  of  cooling 
produce  very  profound  effects  upon  the  physical  properties  of  the  metal, 
this  process  is  not  as  simple  as  it  appears.  The  effects  of  cooling  at  different 
rates  and  in  different  ways  should,  then,  be  carefully  studied.  The  property 
most  noticeably  affected  by  the  cooling  process  is  the  hardness.  As  is 
well  known,  this  property  in  a  given  steel  depends  upon  the  rate  of  cooling 
from  above  the  critical  range.  Thus,  by  the  most  rapid  cooling,  it  is  possible 
to  develop  the  maximum  hardness,  or  by  the  slowest  cooling  the  greatest 
softness,  and  by  varying  the  rate  of  cooling  any  degree  of  hardness  between 
these  extremes  may  be  obtained.  In  searching  for  a  reason  for  these  changes 
in  properties,  it  is  not  surprising  that  investigators  have  found  that 
important  structural  changes  accompany  all  cooling,  and  that  these  changes 
vary,  in  the  effects  they  produce,  with  the  speed  of  the  cooling. 

iSteel  and  Its  Heat  Treatment,  Second  Edition,  pp.  133  to  148. 


ANNEALING  543 


Effect  of  Cooling  on  the  Net  Work:  The  first  of  these  structural 
changes  that  may  be  mentioned  is  the  effect  of  different  rates  of  slow  cooling 
upon  the  net  work  of  ferrite  described  in  the  preceding  section  of  this  book. 
Thus,  in  very  slow  cooling  of  hypo-eutectoid  steels  from  the  annealing 
temperature  a  coalescence  of  the  excess  ferrite  into  large  grains  intermingling 
with  coarse  pearlite  grains  results.  If  the  steel  be  now  cooled  rather  rapidly, 
but  still  not  so  rapidly  as  to  prevent  the  formation  of  pearlite,  the  excess 
ferrite  will  be  found  to  be  of  a  fine  grain  structure  and  to  form  a  fine  network 
about  the  pearlite.  If,  now,  these  two  methods  be  combined,  that  is,  if 
the  cooling  be  made  to  proceed  rapidly  through  the  upper  part  of  the  trans- 
formation range  then  slowly  to  atmospheric  temperature,  the  net  work  of 
ferrite  is  fine,  but  the  pearlite  is  better  developed  than  in  the  second 
case. 

The  Effect  of  Cooling  Upon  Pearlite  now  remains  to  be  explained. 
While  the  rate  of  cooling  from  below  the  critical  range  can  have  no  effect 
upon  the  pearlite,  changing  the  rate  of  cooling  while  the  steel  is  passing 
through  this  range  and  the  solid  solution  is  being  transformed  into  pearlite 
will  correspondingly  change  the  arrangement  of  the  ferrite  and  cementite 
composing  the  pearlite,  so  that  the  same  steel  may  be  made  to  exhibit 
widely  differing  physical  properties.  As  mentioned  before,  the  austenite 
does  not  pass  directly  into  the  pearlitic  condition  on  cooling  through  the 
critical  range,  but  makes  the  change  by  way  of  the  three  transition  stages 
known  as  martensite,  troostite,  and  sorbite.  Of  these,  only  sorbite  is 
retained  in  the  steel  by  annealing  methods  of  cooling.  In  small  sections 
it  is  retained  by  air  cooling  through  the  lower  critical  range.  By  varying 
the  cooling  through  this  range  this  change  from  sorbite  to  pearlite  may 
be  controlled  so  as  to  produce  five  phases,  or  varieties,  of  pearlite  having 
different  physical  properties  as  follows: — • 

1st  Phase.  True  Sorbite  with  emulsified  FesC.  Very  dark  on  etching. 
Tensile  strength,  150,000.  Elongation,  10%  in  two  inches. 

2d  Phase.  Sorbitic  pearlite  with  semi  segregated  FeaC.  Dark  on 
etching.  Tensile  strength,  125,000.  Elongation,  15%  in  two  inches. 

3d  Phase.  Finely  laminated  pearlite  with  FesC  almost  completely 
segregated.  Exhibits  a  play  of  gorgeous  colours  when  lightly  etched. 
Tensile  strength,  100,000.  Elongation,  10%  in  two  inches. 

4th  Phase.  Fully  laminated  pearlite  with  completely  segregated  Fe^C. 
Tensile  strength,  85,000.  Elongation,  8%  in  two  inches. 

5th  Phase.  Massive  pearlite,  consisting  of  coagulated  FesC.  and 
ferrite.  Tensile  strength,  75,000.  Elongation,  5%  in  two  inches. 

The  second  phase  is  the  one  sought  in  the  process  of  patenting  in  wire 
drawing.  So,  it  is  seen  that,  having  obtained  the  greatest  possible  refine- 
ment as  to  grain  size  and  released  all  the  internal  stresses  and  strains  in  the 
metal  by  heating  to  the  proper  temperature,  it  still  remains  to  adjust  the 
physical  properties  by  regulating  the  rate  and  the  manner  of  cooling. 


544 


THE  TREATING  OF  STEEL 


1.     Sorbite.     Cementite  is  emulsified. 
Obtained    in   steels    of    low   carbon   content    by 
cooling  rapidly  to  atmospheric  temperatures. 


2.  Sorbitic  Pearlite.  Cementite  is  partly 
segregated.  Obtained  by  cooling  rapidly  through 
the  upper  range  only. 


3.     Pearlite.     Cementite  is  largely  segregated. 
Obtained  by  moderately  slow  cooling. 


4.     Laminated  Pearlite.       Cementite  is  com- 
pletely segregated.    Obtained  by  slow  cooling. 


5.  Massive  Pearlite.  Cementite  and  ferrite 
are  coagulated.  Obtained  by  very  slow  cooling 
to  atmospheric  temperatures. 


FIG.  113.  Microphotographs  Showing  Progressive  Segregation  of  Cementite  in  the 
Development  of  Pearlite  from  Sorbite.  (White  areas  represent  ferrite,  black 
areas,  Cementite.) 


ANNEALING  546 


Other  Factors  to  consider  in  cooling  are  the  carbon  content  and  the 
size  of  the  object.  In  general,  the  lower  the  carbon  the  more  rapid  may 
be  the  rate  of  cooling  without  affecting  to  any  marked  degree  the  softness 
and  ductility  of  the  metal.  For  example,  steels  containing  less  than  .15% 
carbon  may  even  be  quenched  in  water,  and  those  containing  less  than 
.30%  carbon,  in  oil,  without  markedly  decreasing  their  ductility.  In  order 
to  secure  the  same  rate  of  cooling  in  objects  of  different  size,  it  is  obviously 
necessary  to  regulate  the  external  conditions  in  accordance  with  the  dimen- 
sions of  the  objects  treated.  Thus,  the  cooling  in  air  of  a  very  fine  wire 
may  be  equivalent  to  quenching  in  oil  or  water  an  axle  of  the  same  carbon 
content. 

Methods  of  Cooling:  In  general,  there  are  three  methods  of  cooling, 
namely,  furnace  cooling,  insulated  cooling  and  air  cooling.  Of  these,  furnace 
cooling  may  be  made  the  slowest,  especially  if  the  furnace  is  large  and  can 
be  effectually  sealed  from  air  draughts.  This  method  gives  maximum 
softness  and  ductility.  In  other  words,  the  tensile  strength  and  elastic 
limit  will  be  at  their  lowest,  while  the  elongation  and  reduction  in  area 
will  be  at  or  near  their  maxima.  Steel  subjected  to  such  treatment  will 
resist  severe  distortions.  In  what  has  been  termed  above  as  insulated 
cooling,  the  object  is  removed  from  the  furnace  and  covered  with  a  blanket 
of  lime,  sand,  ashes,  etc.,  or  it  may  be  placed  in  a  brick  or  concrete  lined 
underground  pit  with  a  tight  fitting  cover,  which  in  turn  may  be  covered 
with  ashes  or  loose  earth.  In  cases  where  large  amounts  of  steel  are  placed 
in  a  single  pit,  thia  method  may  be  slower  even  than  furnace  cooling.  In 
air  cooling,  the  object  is  simply  removed  from  the  furnace  and  allowed  to 
cool  in  the  air.  Evidently,  the  rate  of  cooling  by  this  method  will  be  affected 
by  the  size  of  the  piece  and  the  season  of  the  year.  In  addition  the  physical 
properties  imparted  will  depend  somewhat  upon  the  carbon  content.  Hence, 
the  American  Society  for  Testing  Materials  recommends  that  "Thick 
objects  with  less  than  0.50%  of  carbon  may  be  cooled  completely  in  air, 
of  course,  protected  from  rain  or  snow.  Objects  with  0.50%  of  carbon  or 
more,  and  thin  objects  with  from  0.30%  to  0.50%  of  carbon,  may  be  cooled 
in  air  if  their  cooling  is  somewhat  retarded,  as  for  instance,  by  massing 
them  together,  as  happens  in  the  case  of  rails.'7  The  effect  of  the  more 
rapid  cooling  in  air  is  to  increase  the  strength  and  elastic  limit,  but  lower 
the  reduction  and  elongation.  In  order  to  hasten  the  cooling,  articles  of 
low  carbon  content  are  sometimes  immersed  in  water  after  they  have 
become  black  in  color.  This  method  is  then  called  water  annealing. 

Combination  Methods  of  Cooling:  Besides  the  three  general 
methods  of  cooling  described  above,  various  combination  methods  have 
been  employed  with  great  success.  Three  of  these,  as  directed  by  Bullens, 
are  as  follows: 

1.  "Heat  to  slightly  over  Acs,  air  cool  to  just  over  Ar1;  return  to  a 
furnace  which  is  held  at  that  temperature  (about  725  °C.),  heat  until 


546  THE  TREATING  OF  STEEL 

uniform,  and  then  cool  slowly.  The  latter  heating  should  not  be  any 
longer  than  is  possible.  This  method  will  tend  to  prevent  the  formation 
of  large  amounts  of  free  ferrite,  but  will  affect  the  pearlite,  as  there  will 
be  slow  cooling  through  the  Arx  range.  2.  Heat  to  slightly  over  the  Ac3 
range,  air  cool  to  just  under  the  Arx  range,  return  to  a  furnace  and  heat  to 
730°  C.  and  slow  cool.  This  method  will  effect  a  greater  toughening,  if 
the  temperature  has  not  been  prolonged  too  greatly  at  the  second  heating. 
3.  Heat  to  slightly  above  Acg  air  cool  to  below  Ar^,  return  to  a  furnace 
heated  at  a  temperature  slightly  below  Ar±  (660°  to  670°  C.),  hold  at  this 
temperature  until  uniformly  heated,  and  slow  cool  (in  lime  or  air).  By 
permitting  the  steel  to  air  cool  to  a  temperature  below  the  lowest  trans- 
formation, advantage  is  taken  of  any  'hardening  effect'  or  retardation  in 
the  transformation  of  austenite  into  a  conglomerate  of  pearlite  and  ferrite. 
This  effect  will  increase  with  the  percentage  of  carbon  and  the  smaller  the 
size  of  the  piece.  The  reheating  to  a  temperature  below  the  lower  critical 
range,  if  not  prolonged,  will  neither  change  the  grain  size  nor  allow  of  the 
coalescing  of  the  excess  ferrite  or  of  the  individual  constituents  of  the 
pearlite,  but  will  form  a  mass  of  irresolvable  and  intermixed  pearlite  and 
ferrite  known  as  'sorbite.'  At  the  same  time,  however,  it  will  give  the 
maximum  combination  of  large  ductility,  good  strength  and  excellent 
machining  properties.  This  method  is  of  particular  value  in  the  annealing 
of  tool  steels,  in  which  it  has  given  most  excellent  results." 

Double  Annealing  consists  in  heating  the  steel  to  a  temperature  con- 
siderably over  the  Acs  point,  cooling  rapidly  to  some  point  below  the 
lower  transformation  range,  then  immediately  reheating  to  a  point  slightly 
under  or  over  Aci,  and  finally  cooling  slowly.  This  method  is  employed  to 
relieve  the  most  severe  strains,  which  do  not  respond  readily  to  ordinary 
annealing.  The  high  first  annealing  temperature  effaces  the  strains,  while 
the  rapid  cooling  prevents  their  returning.  As  this  cooling  tends  to  harden 
the  metal,  the  second  process  is  necessary  to  soften  it  and  refine  the  grain, 
coarsened  by  the  first  operation,  as  much  as  possible.  The  second  heating, 
of  course,  may  be  to  a  temperature  just  above  Acs,  when  even  better  results 
should  be  obtained,  provided  softness  is  the  chief  end  sought. 

Box  Annealing:  In  many  instances,  especially  with  tool  steel,  it  is 
important  that  the  surface  be  protected  from  oxidation,  or  decarbonization. 
Some  furnaces  are  now  designed  so  that  the  object  being  heated  may  be 
surrounded  by  a  reducing  atmosphere,  and  so  oxidation  is  prevented.  Where 
such  furnaces  are  not  provided,  it  is  the  practice  to  pack  the  object  in  a 
metal  box,  called  an  annealing  box,  with  some  refractory  material,  such  as 
sand,  ground  mica,  etc.,  in  the  case  of  low  carbon  steel,  or  with  some  reducing 
substances,  as  for  example  a  mixture  made  up  of  a  little  charcoal  with 
ashes,  burned  bone,  etc.,  in  the  case  of  higher  carbon  steels,  like  the  tool 
steels,  for  example. 


ANNEALING  547 


Annealing  Hyper=Eutectoid  Steels:  In  annealing  hyper-eutectoid 
steels,  as  in  the  case  of  hypo-eutectoid  steels,  one  or  more  of  these  objects 
are  aimed  at;  (1)  release  of  strains,  (2)  softening  in  preparation  for  machin- 
ing, and  (3)  change  of  structure.  The  first  object  may  be  accomplished 
by  a  simple  reheating  at  temperatures  considerably  below  those  of  the 
critical  range.  The  second  and  third  objects  are  more  difficult  to  attain, 
for  the  treatment  administered  will  be  governed  by  the  amount  of  the  excess 
cementite  and  the  form  in  which  it  exists.  Thus,  if  the  cementite  is  partly 
diffused,  that  is,  does  not  exist  as  a  net  work  or  as  spines  and  needles,  and 
the  grain  size  is  small,  conditions  that  may  generally  be  expected  in  high 
carbon  tool  steels,  the  forging  hardness  may  be  largely  removed  by  anneal- 
ing at  a  temperature  slightly  under  Ac.  or  between  600 °C  and  700 °C.  The 
steel  should  not  be  kept  at  this  temperature  any  longer  than  is  necessary  to 
heat  it  thoroughly  and  uniformly  throughout,  as  prolonged  heating  may 
cause  the  excess  cementite  to  coagulate.  Such  treatment  will  release  the 
strains  and  soften  the  steel  sufficiently  for  machining.  On  the  other  hand, 
if  the  grain  is  coarse,  making  a  complete  change  in  structure  desirable,  it 
will  be  necessary  to  heat  to  a  temperature  in  excess  of  the  Aci-2-s  point,  or 
above  725  °C.  For  steels  with  a  carbon  content  approximating  0.90%,  such 
heating  will  bring  about  a  complete  change  of  structure  and  give  the  finest 
grain-size  obtainable  through  annealing.  For  steels  with  a  carbon  content 
considerably  in  excess  of  the  eutectoid  ratio  the  annealing  may  be  done  at 
similar  temperatures,  provided  the  excess  cementite  is  more  or  less  in 
solution.  If  the  cementite  is  not  in  solution  and  a  maximum  refinement  is 
desired,  the  steel  may  be  oil  quenched  from  a  temperature  somewhat  over 
the  Aci-2-s  range,  and  subsequently  annealed  at  a  temperature  just  below 
that  range,  or  it  may  be  normalized  and  annealed. 

Normalizing  and  Spheroidizing:  These  are  two  processes  applied  to 
hyper-eutectoid  steels  in  particular,  though  normalizing  is  often  applied  to 
hypo-eutectoid  steels  also.  If  the  free  cementite  in  the  former  steel  exists 
as  a  network  or  as  spines,  which  would  make  the  steel  difficult/ to  machine, 
annealing  at  the  usual  temperatures  (Aci-2-s)  Wl^  not  affect  this  cementite, 
but  will  simply  refine  the  ground  mass.  In  order  to  eliminate  this  free 
cementite,  it  is  necessary  first  to  normalize,  that  is,  quench  the  steel  from 
a  temperature  above  that  of  the  Accm  range.  Usually,  air  cooling  from 
a  temperature  of,  say,  960°  C.,  or  1000°  C.,  will  not  permit  the  cementite 
to  recoagulate.  Lower  carbon  steels  are  heated  to  about  the  same  tem- 
perature, but  quenching  is  never  required.  Hence,  in  practice,  normalizing 
usually  consists  in  heating  the  steel  to  the  temperatures  mentioned  and 
cooling  simply  in  air.  The  annealing  may  then  be  carried  out  at  a  tem- 
perature of  745°  C.  or  over,  to  secure  the  refining  of  the  grain  size  and 
complete  softening  of  the  steel.  The  heating  for  annealing  should  be  just 
as  short  as  possible  in  order  to  prevent  the  separation  of  the  excess  cementite 
again.  The  method  given  above  may  be  modified  for  hyper-eutectoid  steel 
by  annealing  at  a  temperature  slightly  under  the  lower  critical  range  instead 


548  THE  TREATING  OF  STEEL 

of  over  it.  This  method,  however,  is  subject  to  the  objection  that  the  steel 
will  not  be  refined,  but  will  possess  a  large  grain  size  on  account  of  the  high 
normalizing  temperature.  But  on  the  other  hand,  the  lower  annealing  tem- 
perature entirely  prevents  the  formation  of  free  cementite  either  as  spines 
or  as  a  network,  and  the  excess  cementite  is  thrown  out,  under  these  con- 
ditions, as  little  nodules  or  "spheroids,"  if  the  reheating  temperature  has 
been  near  the  end  of  the  lower  critical  range.  Spheroidal  cementite  may 
also  be  obtained  by  cooling  very  slowly  through  the  end  of  the  Art  trans- 
formation range.  Spheroidizing  is  a  great  help  in  the  machining  of  high- 
carbon  steels. 

SECTION    II. 

HARDENING. 

The  Hardening  Operation :  The  operation  of  hardening  as  applied 
to  steels  containing  a  sufficient  amount  of  carbon  consists  fundamentally 
of  the  two  operations  of  heating  to  a  suitable  temperature  and  suddenly, 
or  rapidly,  cooling.  The  heating  may  be  accomplished  in  a  number  of 
ways,  varying  from  costly  and  specially  designed  furnaces  and  baths  heated 
with  gas  or  electricity  to  the  simple  forge  fire  of  the  blacksmith;  but  the 
cooling  is  always  brought  about  by  plunging  the  steel  into  a  suitable  liquid, 
a'process  called  quenching.  Let  the  means  be  what  they  will,  in  properly 
hardened  steel  the  original  structure,  as  it  existed  before  the  hardening 
process,  such  as  coarse  grain  size,  network,  etc.,  has  entirely  disappeared 
and  has  been  replaced  by  a  new  structure,  totally  different  from  that  of  the 
unhardened  steel.  To  understand  thoroughly  the  hardening  process  a  close 
study  of  the  two  operations  by  which  these  changes  are  brought  about 
should  be  made. 

Heating  for  Hardening:  The  structural  changes  that  accompany  the 
heating  of  steel  through  its  critical  ranges  have  already  been  briefly 
described.  Graphically,  these  changes  are  represented  in  the  central  part  of 
the  accompanying  diagram  (Fig.  114),  depicting  the  heating  and  cooling  of  a 
steel  with  a  carbon  content  of  about  .90%.  From  this  evidence  it  will  be 
seen  that  the  function  of  the  heating  is  to  bring  about  the  proper  change  in 
structure  so  as  to  obtain  (1)  the  formation  of  the  hard  constituents  of  the 
steel  and  (2)  the  smallest  grain  size,  or  highest  refinement  of  the  crystalline 
structure.  From  what  has  already  been  said,  these  structural  changes  can 
be  obtained  only  by  heating  the  steel  above  its  critical  range.  Any  attempt 
at  hardening  it  at  a  temperature  inferior  to  this  range  results  in  only  a  very 
slight,  if  any,  increase  of  the  hardness.  Again,  the  metal  should  not  be 
heated  much  above  the  top  range,  for  then  its  grain  structure  is  coarsened,  as 
has  been  previously  explained,  also,  and  no  additional  hardness  is  imparted. 
Clearly,  the  best  temperature  to  which  the  steel  should  be  heated  is  one 
just  above  the  critical  range.  The  proper  temperature  to  which  plain 
carbon  steels  should  be  heated  is  the  same  as  for  the  true  annealing  of  the 
same  steels.  What  has  been  said  about  the  rate  of  heating  and  the  influence 


HARDENING 


549 


of  size  of  section  in  annealing  also  applies  to  heating  for  hardening. 
If  any  difference,  additional  emphasis  should  be  placed  on  the  uniformity  of 
heating.  The  rule  for  heating  may  be  put  thus:  Heat  slowly,  uniformly, 
and  thoroughly,  to  the  lowest  temperature,  and  no  higher,  that  will  give 
the  desired  results.  To  meet  these  requirements,  the  final  heating  of  steel 
for  hardening  is  often,  and  commendably  so,  conducted  in  baths  of  molten 
lead  or  of  the  chlorides  of  sodium,  calcium,  potassium  or  barium. 


Effect  of  cooling  at  different 
rates  from  above  the  critical 
range. 


Effect  of  rapid  cooling  from 
different  points  relative  to 
the  critical  range. 


Legend:    P=Pearlite,    A=Austenite,    M=Martensite,    T=Troostite, 
S=Sorbite. 

PIG.  114.     Diagram  Depicting  the  Different  Methods  by  Which  the  Five  Different 
Structural  Constituents  of  Eutectoid  Steel  May  Be  Obtained.     (After  Sauveur.) 


Cooling  for  Hardening:  Thus  it  is  seen  that  heating  for  both  anneal- 
ing and  hardening  are  very  similar,  and  that  the  changes  wrought  in  the 
microscopic  constituents  of  the  steel  are  the  same  in  both  cases.  The  main 
difference  in  the  two  operations  is  found  in  the  rate  of  cooling  through  the 
critical  ranges,  at  least.  For  hardening,  this  cooling  must  be  very  rapid, 
whereas  in  annealing  it  was  characterized  as  slow.  The  transitions  attend- 
ing the  transformation  of  austenite  to  pearlite  on  slowly  cooling  through 
the  critical  ranges  have  been  described.  It  will  be  recalled  that  this  trans- 
formation is  not  instantaneous,  nor  is  it  direct,  but  takes  place  by  stages 
through  transitional  structures  called  martensite,  troostite,  and  sorbite, 
the  order  on  slow  cooling  being  from  austenite,  to  martensite  to  troostite, 
to  sorbite,  to  pearlite.  On  heating,  this  order  is  reversed.  It  now  may 
be  explained  that  the  secret  of  the  hardening  process  is  revealed  by  the 
fact  that  rapid  cooling  through  the  critical  range  may  prevent  this  trans- 
formation in  part  or  in  whole,  depending  on  the  rate  of  the  cooling.  Thus, 
by  the  most  rapid  cooling,  the  steel  at  atmospheric  temperatures  is  found 
to  consist  almost  entirely  of  austenite,  while  a  little  slower  cooling  pro- 
duces martensite;  still  slower,  troostite;  slow,  sorbite;  and  very  slow, 
pearlite.  Incidentally,  it  may  be  remarked  that  the  constituents  found  in 
the  steel  after  treating  also  depends  on  the  temperature  within  the  critical 


550 


THE  TREATING  OF  STEEL 


range  at  which  the  rapid  cooling  begins  and  the  carbon  content  of  the  steel, 
because  these  constituents  are  formed  at  different  temperatures  and  the 
presence  of  carbon  retards  the  transformation.  Since  the  properties  of  the 
cooled  steel  are  imparted  to  it  by  the  constituent  which  predominates,  a 
study  of  the  characteristics  of  these  transitional  constituents  will,  there- 
fore, be  of  value.  For  the  sake  of  brevity  and  convenience,  this  knowledge 
is  here  put  down  in  tabulated  form. 

Table  60.    Data  with  Reference  to  the  Constituents  of  Hardened  Steel. 


Name 

Nature 

Occurrence 

Temperature  of 
Stability 

Structure 

Physical 
Properties 

Austenite 

Solid  solution  of 

Obtained  in  1.50% 

Normally  in 

Polyhedral 

Varies  with  car- 

FesC in  gamma 

C.  steels  when 

region  between 

grains 

bon       content. 

iron,  Carbon 

quenched    in    ice 

A-l,  2,  3,  and  A 

Very  hard  but 

content   from 

water  from  1050° 

cm.       Becomes 

softer  than 

trace  to  2%. 

C.   Occurs  in  steel 

pearlite  on  cool- 

martensite. 

containing      12% 

ing  slowly  past 

Mn.  and  25%  Ni. 

AIT  more  rapid 

even    after    slow 

cooling      forms 

cooling. 

martensite. 

Martensite 

Solution  of  FesC 

Obtained  easily  by 

Normally         at 

Fibers     or     flat 

Varies  with  car- 

in   beta    iron, 

quenching     small 

slightly      lower 

plates  lying  par- 

bon      content. 

Carbon  content 

bodies   of   hyper- 

temperature 

allel    to    three 

Hardest      con- 

from   trace    to 

eutectoid  steel,  in     than  austenite. 

sides   of   a   tri- 

stituent of  steel 

1%. 

cold  water.    More 

Changes      into 

angle. 

of         eutectoid 

difficult  to  obtain 

troostite. 

composition.   A 

in     low     carbon 

little  less  hard 

steels.    Chief  con- 

than cementite. 

stituent  of  hard- 

ened carbon  tool 

steels. 

Troostite 

Mixture  of  FegC 

Obtained    by    re- 

Normally at 

Slightly  granular 

Intermediate  be- 

in    beta     iron 

heating     marten- 

lower     temper- 

with sorbite  and 

tween    marten- 

crystallized 

sitic  steel  to  400° 

ature  than  mar- 

martensite    in- 

site and  sorbite. 

FesC  and  crys- 

C. or  on  cooling 

tensite. 

termingled  and 

Not  so  hard  as 

tallized      alpha 

relatively     slowly 

with  f  errite  and 

martensite    but 

iron. 

through      critical 

cementite       in 

stronger     and 

range.     Found  in 

hypo-and 

more  ductile. 

center     of     large 

hyper  -eutectoid 

objects   quenched 

steels. 

in  water. 

Neither  pearlite  nor  sorbite  are,  strictly  speaking,  constituents  of 
hardened  steel,  but  the  latter,  on  account  of  its  position  in  the  transforma- 
tion scale,  forms  the  connecting  link  between  hardened  and  annealed  steel, 
hence  may  occur  in  both.  The  nature  and  properties  of  sorbite  have  already 
been  given,  and  it  should  here  be  recalled  that  it  is  the  toughest  constituent 
of  steel.  The  transition  from  austenite  to  pearlite  is  admirably  illustrated 
in  the  preceding  diagram  of  figure  114. 


HARDENING  551 


Cooling  or  Quenching  Media:  Since  the  rate  of  cooling  controls 
the  hardening  process,  the  selection  of  the  proper  quenching  medium  is  a 
matter  of  much  importance.  The  withdrawal  of  heat,  the  only  function 
of  a  quenching  liquid,  from  the  metal  immersed  in  it  depends  upon  its 
quantity,  its  specific  heat,  its  conductivity,  its  viscosity,  its  volatility,  its 
latent  heat  of  vaporization,  and,  to  some  extent,  its  initial  temperature. 
The  quantity  and  specific  heat  of  the  liquid  control  the  quantity  of  heat 
the  bath  can  absorb  with  a  given  rise  in  temperature.  The  viscosity  affects 
the  flowing  properties  of  the  liquid,  hence  the  convection  of  heat  by  it,  and 
therefore  is  a  factor  in  the  cooling  properties  of  the  liquid,  for  it  is  by  con- 
vection and  conduction  that  the  heat  is  carried  away  from  the  steel  to 
distant  parts  of  the  bath.  The  volatility  indicates  the  temperature  at 
which  the  liquid  will  become  a  vapor  and  form  bubbles  of  gas  on  the 
surface  of  the  steel,  which  tend  to  retard  the  cooling.  Evidently,  if  the 
latent  heat,  or  heat  of  vaporization,  is  high  the  volatility  may  be  relatively 
low,  for  then  much  heat  is  required  to  change  the  liquid  to  the  gaseous 
state.  Since  the  speed  at  which  heat  is  transferred  from  one  body  to 
another  varies  directly  as  the  difference  in  their  temperatures,  it  is  evident 
that  the  initial  temperature  of  the  quenching  liquid  must  affect  the  rate 
of  cooling.  Thus,  water,  one  of  the  most  efficient  media  for  rapid  cooling 
in  use  commercially,  has  high  specific  and  latent  heats,  and  its  viscosity 
is  very  low,  properties  favoring  its  cooling  power,  while  its  volatility  and 
conductivity  are  both  low,  properties  against  it  as  a  quenching  agent. 
Then  just  next  to  water  in  cooling  power  comes  mercury,  which  has  a  lower 
specific  heat,  a  lower  heat  of  vaporization  and  higher  viscosity  than  water; 
but  it  is  less  volatile  and  is  a  very  much  better  conductor  of  heat.  Thus, 
while  the  one  owes  its  cooling  power  to  one  set  of  properties,  the  other  is 
almost  as  efficient  because  of  an  altogether  different  set.  A  solution  of 
salt  in  water,  brine,  is  a  little  more  rapid  than  water,  while  water  sprayed 
under  pressure  upon  the  metal  is  a  quicker  cooling  agent  than  either  water 
or  brine.  After  water,  the  chief  quenching  media  in  use  commercially  are 
the  oils,  all  of  which  are  much  slower  than  water.  An  interesting  experi- 
ment reported  by  Messrs.  Matthews  and  Staggl  is  intended  to  show  the 
quenching  properties  of  the  various  liquids  that  are  employed  in  com- 
mercial hardening.  In  this  experiment  a  suitable  test  piece  of  steel  was 
carefully  heated  to  1200°  F.  and  quenched  in  25  gallons  of  the  medium 
under  examination,  and  the  time  required  to  cool  the  steel  to  700  °F.  noted 
with  a  stop  watch,  as  well  as  the  rise  in  temperature  of  the  medium.  In 
each  medium  this  operation  was  repeated  successively  until  the  medium 
had  either  reached  its  boiling  point  or  a  temperature  of  250°  F.  The  results 
of  this  experiment  were  then  plotted  somewhat  as  shown  in  the  accom- 
panying diagram. 

Combination  Methods  of  Quenching:  Besides  the  straight  water  or 
oil  quenching  and  water  spraying,  many  special  quenching  methods  and 
media  have  been  tried.  Many  of  the  latter  are  fakes,  but  the  three  follow- 

iSee  "Factors  in  Hardening  Tool  Steel"  by  Matthews  and  Stagg.  American 
Society  of  Mechanical  Engineers,  1915. 


552 


THE  TREATING  OF  STEEL 


ing  special  methods  of  quenching  have  proved  of  great  value.  Thus,  when 
high  tensile  strength  is  required,  yet  on  account  of  the  size  of  the  piece  or 
the  chemical  composition — manganese  too  high,  for  example — water 
quenching  is  unwise,  the  bath  of  water  may  be  covered  with  oil  to  an  equal 
depth,  so  that  the  piece  upon  being  lowered  into  the  bath  is  partly  cooled 
in  this  oil,  which  then  forms  a  film  over  the  surface  that  retards  the  cooling 
by  the  water  somewhat.  This  method  is  sometimes  applied  to  large 
forgings,  such  as  axles.  For  small  tools  a  thin  film  of  oil  on  the  water 
suffices.  Another  method,  used  by  some  tool  hardeners,  consists  of  first 
plunging  the  tool  into  water  to  remove  a  part  of  the  heat,  then  into  oil  till 
the  cooling  is  complete.  Information  as  to  what  is  aimed  at  by  this  method 
is  not  at  hand,  but  it  is  evident  that  the  method  is  not  so  severe  as  straight 
water  cooling.  Where  great  toughness  with  little  hardness  is  required,  the 
article  may  be  plunged  into  and  forcibly  submerged  in  molten  lead,  as  this 
manner  of  quenching  produces  sorbite  in  steels  under  the  eutectoid  in 
composition. 


2 1     3  457  6        8 


10  11 


250 


200 


150 


o 

g  100 


a  so 


8    9 


BW 


50 


100 


150 


200 


Time  in  Seconds  Required  to  Cool  Test  Piece  from  1200°  F  to  700°  F. 
Legend : 


6— New  Bleached  Fish  Oil. 
7— New  Cotton  Seed  Oil. 

Cotton  Seed. 


B— Brine. 
W— City  Water. 

1— New  Fish  Oil. 

2— No.  2  Lard  Oil. 

3— Lard  Oil  in  Use  Two  Years.  9— Mineral  Tempering  Oil. 

4 — Boiled  Linseed  Oil.  10 — Dark  Mineral  Tempering  Oil. 

5— Raw  Linseed  Oil.  11— Very  Viscous  Tempering  Oil. 

NOTE.     10  and  11  are  similar  to  cylinder  oils. 

FIG.  115.     Diagram  Illustrating  Approximately  the  Quenching  Power  of  Various 
Liquids.     (Data  by  Messrs.  Matthews  and  Stagg). 


HARDENING  553 


Manher  of  Quenching:  Much  skill  is  required  on  the  part  of  the 
operator  in  the  quenching  of  steel  to  prevent  cracking  and  warping.  Both 
defects  are  due  to  unequal  or  non-uniform  cooling  of  the  different  parts  of 
the  piece,  and  are  more  liable  to  occur,  for  obvious  reasons,  in  bodies  of 
large  size  or  of  irregular  section.  It  is  to  overcome  this  danger  that  large 
axles  are  hollow  bored  before  treatment.  All  large  sections,  if  solid,  must 
be  reheated  immediately  after  hardening  in  order  to  relieve  the  internal 
stresses  and  strains,  else  incipient  fractures  will  result.  Warping  will 
always  occur  in  small  sections,  if  the  quenching  is  not  uniform.  As  warping 
more  often  results  when  the  piece  is  plunged  into  the  quenching  bath  at  an 
angle,  it  is  always  best  to  quench  vertically,  in  the  direction  of  greatest 
length,  whenever  such  procedure  is  possible. 

Progressive  Hardening:  Progressive,  or  differential  hardening,  is 
accomplished  by  quenching  only  a  part  of  the  object.  In  such  a  method  the 
heat  is  slowly  withdrawn  from  the  part  furthest  from  the  quenching  liquid, 
but  more  and  more  rapidly  as  the  part  quenched  is  approached,  so  that 
the  steel  becomes  progressively  softer  and  tougher  from  the  hardened  part. 
By  withdrawal  of  the  piece  before  cooling  is  complete,  the  heat  in  the 
unquenched  part  may  be  made  to  temper  the  hardened  portion.  In  this 
method  care  is  needed  to  avoid  hardening,  or  quenching,  rings,  which  form 
if  the  piece  is  held  in  the  quenching  bath  at  a  uniform  depth.  To  avoid 
them  the  piece  should  be  raised  and  lowered  during  the  quenching.  This 
method  is  employed  in  treating  such  tools  as  anvils,  die  blocks,  edged 
tools,  pointed  tools,  etc. 

Hardening  Eutectoid  Steels  (C.  .80  to  1.00%):  Steel  of  eutectoid 
composition  possesses  the  maximum  hardening  power,  that  is,  the  difference 
in  hardness  between  the  quenched  and  unquenched  article  of  eutectoid 
composition  is  greater  than  that  in  any  other  grade  of  the  plain  steels.  So, 
this  statement  does  not  mean  that  quenched  eutecoid  steels  are  the  hardest 
steels,  for  hyper-eutectoid  steels  may  show  much  greater  hardness  both 
before  and  after  hardening  than  eutectoid  steels,  due  to  the  presence  of 
free  cementite  or  to  more  highly  carbonized  martensite,  but  their  gain  in 
hardness  on  quenching  is  less.  It  is  clear  that  eutectoid  steels  should  be 
hardened  from  a  temperature  just  above  Aci,  that  is,  750°  to  800°  C.,  for 
at  this  temperature  the  carbon,  being  in  solution  and  thoroughly  diffused, 
possesses  its  full  hardening  power,  and  the  grain  structure  is  at  its  finest. 
For  the  maximum  hardness,  the  metal  should  then  be  quenched  as  suddenly 
as  possible  in  water,  by  which  treatment  the  austenite  is  changed  into  a 
fine  grained  martensitic  or  troostito-martensitic  structure,  depending  upon 
the  size  of  the  article  and  other  incidental  conditions.  In  order  to  avoid 
the  danger  of  cracking,  many  operators  will  prefer  to  quench  in  oil,  when 
troostite  may  be  the  predominating  constituent  if  the  piece  is  of  large  size. 

Hardening  Hyper=Eutectoid  Steels  (1.00  to  1.50%):  Steels  that 
contain  more  than  .90%  carbon  are  also  hardened  by  heating  just  above 


554  THE  TREATING  OF  STEEL 


Acs-a-i,  or  in  other  words,  at  the  same  temperature  as  steel  of  %utectoid 
composition,  the  reason  for  which  is  readily  seen  by  a  little  reflection.  To 
cite  an  example,  suppose  the  steel  to  be  hardened  has  a  carbon  content  of 
1.30%.  Such  a  steel  in  its  natural  state  is  composed  approximately  of  93% 
pearlite  and  7%  free  cementite.  To  cause  both  pearlite  and  free  cementite 
to  change  to  austenite  would  require  the  steel  to  be  heated  above  Accm> 
about  950°,  but  such  a  high  temperature  would  result  in  a  decided  and  un- 
desirable coarsening  of  the  grain  size,  which  is  avoided  by  heating  only 
above  Ac3~2-i.  Besides,  quenching  from  this  lower  temperature  would 
give  a  harder  steel  than  would  be  obtained  in  the  first  instance.  For, 
supposing  the  quenching  is  such  as  to  produce  martensite,  in  the  first  case, 
the  hardened  steel  would  be  composed  of  martensite  only,  whereas  in  the 
second  instance  it  would  be  made  up  of  93%  martensite  and  7%  free 
cementite,  which  being  harder  than  martensite,  would  impart  additional 
hardness  to  the  quenched  steel.  When  for  any  cause  it  is  desirable  to  avoid 
the  presence  of  any  free  cementite,  the  metal  may  be  heated  above  AcCm 
and  cooled  in  molten  lead,  then  reheated  to  slightly  above  Aci,  and  quenched 
as  usual.  The  quenching  in  lead  prevents  the  re-formation  of  free  cementite 
and  is  not  severe  enough  to  cause  cracking  or  warping,  while  the  reheating 
to  Aci  accomplishes  the  grain  refinement  so  much  to  be  desired  in  these 
steels. 

Hardening  Hypo=Eutectoid  Steels  (C  .30  to  .80%) :  Steel  containing 
less  than  .30%  carbon  cannot  be  materially  hardened  by  any  of  the  ordinary 
commercial  methods  of  quenching  on  account  of  the  separation  of  ferrite 
from  the  solution,  which  takes  place  to  some  extent  even  with  the  most 
rapid  methods  of  cooling.  For  hardening  hypo-eutectoid  steels  with  a 
higher  carbon  content,  two  methods  may  be  employed.  First,  the  metal 
may  be  heated  slightly  above  Aci  and  quenched,  when  only  the  pearlite  of 
the  steel  will  be  affected,  it  being  changed  into  martensite  or  troostite 
according  to  the  rate  of  cooling,  and  the  free  ferrite  will  undergo  no  refine- 
ment at  all.  Evidently,  the  second  and  better  plan  is  to  heat  the  metal 
above  Aca-s,  when  its  entire  bulk  changes  into  hardenable  austenite,  which 
on  quenching  rapidly  may  be  converted  into  martensite  or  at  least  troostito- 
martensite.  While  this  martensite,  because  of  its  lower  carbon  content,  is 
not  so  hard  as  the  martensite  formed  from  the  pearlite  in  the  first  method, 
the  steel  as  a  whole  will  be  harder  and  certainly  more  uniform  and  of  a 
much  finer  grain  structure,  because  the  original  network  of  coarse  ferrite 
will  have  been  absorbed  and  refined. 


SECTION  IIIo 

THE   TEMPERING   OF   HARDENED   STEEL. 

The  Tempering  Process :  Tempering,  sometimes  spoken  of  as  drawing- 
back  or  simply  as  drawing,  consists  in  reheating  the  metal  after  hardening 
to  some  temperature  below  the  critical  ranges,  and  may  have  for  its  primary 


TEMPERING  AND  TOUGHENING 


555 


object  (1)  the  regulation  of  the  hardness  and  brittleness  of  the  steel,  (2) 
the  toughening  of  it,  or  (3)  the  release  of  the  hardening  strains.  In 
tempering,  the  release  of  the  internal  stresses  and  strains  set  up  by  the 
hardening  process  is  always  aimed  at,  whatever  may  be  the  other  results 
sought,  for  the  metal  is  incapable  of  giving  its  best  service  as  long  as  these 
or  similar  strains  exist.  This  result  is  usually  accomplished  by  the  heating 
in  the  tempering  process,  for  even  heating  to  the  temperature  of  boiling 
water  will  relieve  these  strains  to  some  extent.  This  fact  is  often  taken 
advantage  of  to  relieve  strains  when  it  is  not  desirable  to  soften  the  steel 
to  the  extent  that  higher  heating  would  involve. 


Legend 
=Pearlite. 


I  ir 

A=Austenite,    M=Martensite,    T=Troostite,    S=Sorbite, 


I. 


Slowly  cooled. 
(Annealed) 


II. 


Quickly  cooled. 
(Hardened) 


III.     Reheating  Hardened 
Steel  (Tempering). 


FIQ.  116.     Diagram  Depicting  the  Constituents  Formed  on  Slowly   Cooling   and 
Quickly  Cooling  Steel  and  on  Reheating  Hardened  Steel.     (After  Sauveur.) 

Nature  and  Theory  of  Tempering:  According  to  the  retention 
theories  of  hardening,  which  are  among  the  most  plausible  ones  advanced 
to  account  for  the  hardening  and  tempering  of  steel,  hardened  steel  is  in 
a  state  of  unstable  equilibrium,  or  strain,  and,  therefore,  is  ever  tending  to 
assume  a  more  stable  form  or  condition,  which  tendency  implies  a  return  of 
the  iron  to  the  alpha  form  and  of  the  carbon  to  the  condition  of  cement 
carbon,  or  segregated  cementite.  In  hardened  steel,  this  transition  is 
prevented  by  the  rigidity  of  the  metal,  which  is  reduced  by  reheating. 
The  extent  of  this  reduction  of  the  rigidity  being  in  proportion  to  the  extent 
of  the  reheating,  the  higher  the  temperature  the  greater  will  be  the  extent 
of  the  transformation.  Thus,  supposing  the  hardening  operation  has 
arrested  the  transition  of  austenite  at  the  martensitic  stage,  this  martensite 
will  begin,  at  a  temperature  some  150°  C.  above  that  of  the  atmosphere  to 
change  into  troostite,  and  the  transformation  will  continue  with  the  rising 
temperature  until  the  martensite  has  passed  entirely  into  troostite,  which 


556  THE  TREATING  OF  STEEL 


result  is  no  sooner  accomplished  than  the  troostite  in  turn  begins  to  change 
into  sorbite.  When  the  temperature  has  been  raised  to  a  point  near  that 
of  the  lower  critical  range,  sorbite,  to  the  exclusion  of  other  constituents, 
will  predominate  the  structure.  Any  higher  heating,  then,  carries  the 
transformation  into  the  critical  ranges,  where  the  order  of  transition  is 
reversed,  sorbite  passing  into  troostite  and  then  to  martensite,  which,  as 
the  temperature,  on  rising,  emerges  from  the  range,  becomes  austenite. 
The  preceding  diagram,  Fig.  116,  copied  after  Sauveur,  will  aid  in  under- 
standing these  changes  when  they  take  place  under  different  conditions. 
Evidently  then,  all  heating  for  tempering  is  conducted  below  the  critical 
range.  By  properly  adjusting  the  temperature  the  transition  described 
above  may  be  arrested  at  any  stage  desired,  and  any  combination 
of  physical  properties  of  which  the  steel  is  capable  may  be  obtained.  It 
is  clear  that  the  manner  of  cooling  from  the  tempering  temperature  is 
immaterial,  though  for  the  sake  of  speed  or  convenience  quenching  or  air 
cooling  is  the  general  practice  in  heat  treating  shops. 

Methods  of  Determining  Tempering  Temperatures:  The  original 
method  of  estimating  tempering  temperatures  is  by  color.  Thus,  if  a  piece 
of  hardened  steel  is  brightened  or  polished  with  a  piece  of  emery,  sand  stone, 
or  other  suitable  means  and  is  then  slowly  heated  in  contact  with  air,  the 
color  of  the  brightened  surface  will,  due  to  the  formation  of  a  surface  film 
of  oxide,  undergo  a  series  of  color  changes,  called  temper  colors,  ranging  from 
faint  yellow  to  blue,  which  will  be  characteristic  of  the  different  temper- 
atures reached  by  continued  application  of  heat.  That  these  colors  are 
indicative  of  a  known  temperature  or  at  least  a  definite  condition  of  the 
hardened  steel  is  generally  accepted;  but  it  is  evident  that  the  method  is 
subject  to  the  objection  that  differences  in  distinguishing  different  colors, 
or  shades  of  color,  is  bound  to  occur  among  different  operators.  Distinction 
of  these  colors  is  also  affected  by  different  light  conditions.  The  same 
temper  will  not  give  the  same  color  in  a  dimly  lighted  room  as  in  a  well 
lighted  one.  While  these  shades  are  hard  to  describe,  the  color  correspond- 
ing to  the  same  temperature  often  being  differently  described  by  different 
individuals,  the  following  table  will  give  some  idea  of  the  colors  corre- 
sponding to  the  different  temperature  changes. 


Table  61.    Tempering  Colors  and  Temperatures  Corresponding 

to  Them. 

Pale  yellow '. 220  deg.  C.  Pale  blue 297  deg.  C. 

Straw 230     "      "    Dark  blue 316     "  " 

Golden  yellow 243     "      "    Red  in  the  dark 400     "  * 

Brown 255     «      "    Red— indirect  sunlight. 525    "  " 

Brown  dappled  with  purple .  .  265     "      "    Red  in  sunlight 580     "  " 

Purple 277     «      «    Dark  Red 700     "  " 

Bright  blue 288     "      " 


TEMPERING  557 


That  the  color  method  has  its  limitations  is  now  well  established,  and 
so  other  methods  are  being  developed  on  a  more  scientific  basis.  These 
methods  involve  the  use  of  sand  baths  or  liquid  baths,  such  as  oil, 
molten  lead,  or  alloys,  fused  salts,  etc.,  for  heating  the  steel  and  the  use 
of  pyrometers  for  controlling  the  temperature,  and  aim  at  the  elimination 
of  the  personal  equation  in  the  results  obtained.  Seeing  that  the  tempering 
action  often  takes  place  very  rapidly  and  that  a  difference  of  15°  or  20° 
of  temperature  will  often  spell  success  or  failure,  such  appliances  would 
appear  to  be  a  very  necessary  part  of  the  equipment  of  the  modern  heat 
treating  shop. 

Influence  of  Time  in  Tempering:  From  what  has  been  said  about 
the  transformations  wrought  in  the  tempering  process,  the  reader  might 
infer  that  the  time  the  steel  is  kept  at  the  tempering  temperature  would 
exert  no  influence.  Lest  such  should  be  the  case,  occasion  is  taken  to 
explain  that,  contrary  to  this  inference  and,  in  fact,  to  the  common  belief, 
maintaining  the  metal  at  the  tempering  temperature  for  a  considerable 
length  of  time  will  result  in  producing  additional  tempering.  This  fact  is 
evidenced  by  the  change  of  the  tempering  colors  at  constant  temperature. 
Thus,  it  has  been  ascertained  that  the  temper  color,  instead  of  remaining 
the  same  at  a  given  temperature,  advances  in  the  tempering  color  scale 
as  it  would  if  the  temperature  were  being  raised,  which  phenomenon  would 
appear  to  indicate  that  the  temper  colors  are  indicative  of  the  tempering 
condition  of  the  steel  rather  than  of  the  temperature.  For  example,  by 
heating  a  steel  to  277°,  where  its  temper  color  is  purple,  and  keeping  it 
there  till  its  color  is  bright  blue,  a  temper  corresponding  to  the  temperature 
288°  is  obtained.  According  to  some  investigators,  however,  the  temper 
will  not  follow  the  color  to  the  end.  They  maintain  that  each  temperature 
has  a  maximum  temper  effect,  which  is  reached  quicker  and  quicker  as 
the  temper  temperature  is  raised. 

Physical  Properties  Affected  by  Tempering:  It  is  to  be  remembered 
that  besides  the  hardness,  the  other  physical  properties  of  the  steel  are 
likewise  affected  by  tempering.  Thus,  as  the  hardness  and  brittleness  are 
decreased,  the  tensile  strength  and  elastic  limit  will  follow  the  hardness 
closely  and  be  correspondingly  decreased,  while  the  ductility,  i.  e.,  elonga- 
tion and  reduction  in  area,  will  be  increased,  though  not  following  in  the 
wake  of  the  hardness  with  the  same  regularity  as  the  tensile  strength  and 
elastic  limit.  (See  table  62,  page  561) 

Tempering  the  Steels  of  Different  Structural  Composition :  Seeing 
that  the  hardening  process  has  developed  a  certain  structure  in  the  steel, 
it  may  be  well,  in  turning  to  the  practical  application  of  the  principles 
and  theories  of  tempering  the  hardened  steels,  to  consider  this  phase  of 
the  subject  from  the  standpoint  of  their  structural  composition.  The 
accompanying  diagram  is  intended  to  depict  the  tempering  of  all  the 
hardened  steels. 


558 


THE  TREATING  OF  STEEL 


Tempering  Austenitic  Steels:  As  has  already  been  shown,  austenite 
does  not  occur  in  steels  hardened  by  any  of  the  commercial  methods. 
Hence,  a  lengthy  discussion  of  the  tempering  of  austenitic  steel  is  out  of 
place  in  this  study.  It  may  be  pointed  out,  however,  that  instead  of  passing 


Critical 
Range 


200 


X  II  III  IV  V  VJ, 

Legend:    A=Austenite,  M=Martensite,  T=Troostite,  S=Sorbite. 
Fie*.  117.     Diagram  Depicting  the  Tempering  of  Hardened  Steel.     (By  Sauveur.) 

into  martensite  then  to  troostite,  as  shown  at  I  in  the  diagram,  austenite 
may  on  tempering,  pass  directly  into  troostite  as  indicated  at  II.  The 
diagram  shows  that  austenite  begins  to  be  transformed  at  a  very  low  tem- 
perature, being  completely  converted  into  martensite  at  200°  C.  or  into 
troostite  at  400°  C. 

Tempering  Martensitic  Steels:  If  steel  of  high  carbon  content  has 
been  fully  hardened  by  quenching  rapidly,  as  in  water,  it  consists  mainly 
of  martensite,  if  other  conditions  were  at  all  favorable.  This  constituent 
is  more  stable  than  austenite,  and  on  tempering  will  begin  to  change  to 
troostite  below  200°  C.  and  this  transformation  is  complete  at  about 
400°  C.,  as  shown  at  III  on  the  diagram.  Recalling  the  properties  of 
troostite,  it  will  be  seen,  then,  that  tempering  between  these  two  points 
results  in  a  material  decrease  of  the  hardness  and  brittleness  accompanied 
by  a  decrease  also  of  tensile  strength  and  elastic  limit,  while  some  increase 
in  the  ductility  will  be  noted.  It  is  to  be  observed  that  just  as  martensite 
predominates  in  the  structure  of  hardened  steels,  and  pearlite,  of  annealed 
steels,  so  the  presence  of  troostite  indicates  tempering,  either  as  a  separate 
reheating  process  or  by  regulating  the  cooling  in  the  hardening  operation, 
as  for  example,  in  oil  quenching,  which  is  often  called  oil  tempering  on  this 
account. 

Tempering  Troostitic  Steels:  Commercially  hardened  steels, 
especially  those  quenched  in  oil,  will  sometimes  show  large  proportions 
of  troostite.  From  the  diagram  it  will  be  seen  that  to  temper  this  steel 
will  require  a  temperature  of  at  least  400°,  the  temperature  at  which  it 
begins  to  be  changed  into  sorbite.  At  600°  C.  the  transformation  of 


TOUGHENING  559 


troostitic  sorbite  is  complete.  Tempering  here  results  in  a  marked  tough- 
ening of  the  steel  with  loss  of  much  of  the  hardness.  Hence,  as  explained 
below,  tempering  between  these  temperatures  is  called  toughening  by 
many  of  the  heat  treating  experts.  However,  troostite  steels  produced 
by  quenching  often  contain  considerable  martensite.  When  such  is  the 
cas,e  the  steel  may  be  softened  by  reheating  to  about  400°  C.,  when  the 
martensite  will  be  destroyed. 

Sorbite:  As  this  constituent  occurs  at  the  top  of  the  tempering 
range,  sorbitic  steels  cannot  be  tempered.  Furthermore,  as  these  steels 
are  not  produced  by  the  regular  hardening  methods,  they  are  not  properly 
considered  in  connection  with  tempering. 

SECTION    IV. 

THE    TOUGHENING   OF   STEEL 

Toughening  is  the  term  applied  to  certain  treatments  given  usually  to 
steels  of  medium  carbon  content  (C.  .35%  to  .60%)  in  which  strength  and 
toughness,  rather  than  hardness  and  toughness,  are  the  properties  sought. 
It  is  a  treatment  applied  to  railroad  axles,  piston  rods,  and  other  articles 
subjected  to  fatigue,  impact  and  dynamic  stresses  in  service.  As  practiced 
by  the  Carnegie  Company,  toughening  consists  in  heating  the  steel  to 
temperatures  varying  from  775 °C  to  850°C,  depending  upon  the  chemical 
composition,  quenching  in  oil  or  water,  and  then  drawing  back  to  such 
high  temperatures,  450°  to  650 °C,  thai  little,  if  any,  of  the  hardness  due  to 
the  quenching  remains. 

Benefits  of  Toughening:  Compared  with  annealing,  toughening  has 
an  advantage  in  that  both  the  strength  and  ductility  of  the  steel  may  be 
increased  to  the  limits  of  which  the  steel  is  capable.  In  annealing,  strength 
is  sacrificed  for  ductility,  but  in  toughening,  the  relation  of  these  properties 
may  be  nicely  controlled.  The  effect  of  the  quenching  operation  is  to  give 
the  greatest  refinement  of  the  grain  and  to  develop  the  maximum  strength 
of  which  the  steel  is  capable.  The  effect  of  the  draw  back  is  to  relieve  all 
strains  due  to  the  quenching,  and,  without  coarsening  the  grain,  develop 
the  ductility,  which  will  gradually  increase,  with  a  partial  loss  in  strength, 
of  course,  as  the  temperature  of  the  draw  back  is  raised.  Between  500°  and 
600  °C  the  draw  back  produces  a  steel  composed  entirely  of  sorbite,  which 
is  the  structure  that  gives  the  highest  combination  of  strength  and 
ductility.  The  pearlite  produced  by  the  usual  annealing  methods  is  both 
less  strong  and  less  ductile  than  sorbite.  One  feature  of  the  toughening 
operation  is  to  increase  the  ratio  of  the  elastic  limit  to  the  ultimate, 
or  tensile,  strength.  Thus,  while  in  natural  and  annealed  steels  of  toughening 
grade  this  ratio  is  approximately  3:6,  in  properly  toughened  steel  it  is 
about  4:6.  In  view  of  the  fact  that  it  is  the  elastic  limit  that  actually 
measures  the  working  strength  of  the  steel,  this  effect  of  toughening  is 
worthy  of  careful  consideration. 

Quenching  for  Toughening:  As  indicated  above,  either  oil  or  water 
is  used  as  a  quenching  medium  for  toughening.  Both  media  have  their 


560 


THE  TREATING  OF  STEEL 


Ladle 
Analysis 

Treatment 

Mechanical 
Properties 

Structure 

. 

^h^ 

C.       .49% 
Mn.   .66% 
P.       .020% 

as 
forged 

Ultimate 
Strength 
96,370  Ibs. 

Elastic 
Limit 
49,310 

m 

" 

S.        .026% 

Elongation 

in  2" 
20.5  % 

|9Bp^ 

Reduction 
of  Area 

34.7% 

x  1  00.  Pearlite  —  Large 

Grain  Size. 

C.       .48% 

Annealed 

Ultimate 
Strength 
85,040  Ibs. 

^^s^ 

'     • 

/• 

^K 

Mn.  .54% 

Heated 

A 

P.       .020% 

to  830  °C 

Elastic 
Limit 
44,920  Ibs. 

§si^P3t 

£i»£Cjp 

S.        .036% 

and  cooled 
in  air 

Elongation 
in  2" 

23% 

Reduction 
of  Area 

37.8% 

'^fe 

ffg/J 

^^^^-isJm.'JsZ^ 

i***^ 

x  100.  Sorbitic  Pearlite  —  Grain  Size  Good. 

C.       .49% 

Quenched 
and 
tempered 

Ultimate 
Strength 
97,200  Ibs. 

^  fl 

,'>X>v 

Mn.  .66% 

P.       .020% 
S.        .026% 

Heated  to 

825  °C  and 
quenched 
in  water 

Elastic 
Limit 
62,720  Ibs. 

Elongation 

in  2" 

25% 

Drawn  back 
at  585  °C 

Reduction 
of  Area 

59.8% 

^^^HHpl 

&£^ 

x  100.    Sorbite  —  Grain  Size  Excellent 

EFFECT  OF  HEAT  TREATMENT 


561 


advantages  and  disadvantages.  Water  is  the  more  rapid  and  drastic 
medium,  and  on  this  account,  is  more  liable  to  develop  cracks  in  the  steel, 
hence  some  heat  treaters  recommend  that  only  oil  be  used.  On  the  other 
hand,  a  deeper  penetration  of  the  effects  of  the  quenching  and  greater 
tensile  strength  and  elastic  limit  are  obtained  with  water  than  with  oil, 
thus  making  it  easier  to  meet  specifications  calling  for  high  tensile  proper- 
ties. Therefore,  others  will  prefer  water  quenching  under  certain  con- 
ditions. In  selecting  the  quenching  medium,  it  is  evident  that  much 
depends  upon  the  article,  its  shape,  size,  and  the  grade  of  steel  it  is  made  of, 
and  much  upon  the  skill  of  the  operator.  All  these  features  of  toughening 
are  brought  out  in  Fig.  118  and  table  62. 


Table  62 11  Illustrating  the  Effect  of  Various  Heat  Treatments  upon 
the  Mechanical  Properties  of  Medium  Carbon  Plain 
Steels. 

Chemical  Composition;  C.  .38%,  Mn.  .55%,  Si.  .05%,  P.  .024%, 

S.  .050%. 
Description  of  Pieces  Treated;  one  inch  rounds,  29  inches  long; 

14  pieces,  all  from  same  billet. 

Description  of  Test  Pieces;  One  test  piece  from  each  of  the  14 
pieces,  turned  to  a  diameter  of  -J/£  inch,  as  in  Fig.  47. 


Heat  Treatment 


Physical  Tests 


Hardening  and 
Refining  Deg.  C 

Anneal 
and  Draw, 
Deg.  C 

Tensile 
Strength 

Elastic 
Limit 

Elongation 
in  2"% 

Reduction 
in  area  % 

Brinell 
Number 

Scleroe- 
copeTest 

As  Rolled 

85,000 

50,000 

30,0 

48.9 

163 

25 

Heated  to  760 

°and' 

cooled  in    f 

urnace 

74,000 

42,500 

32.0 

54.7 

134 

23 

Heated  to  815° 

427° 

100,000 

67,000 

21.0 

53.9 

179 

30 

quenched  in  oil 

482° 

98,000 

66,000 

23.5 

52.8 

170 

29 



538° 

90,000 

59,000 

26.5 

54.7 

170 

29 



593° 

89,000 

58,000 

26.5 

63.5 

170 

29 

649° 

75,000 

53,000 

33.5 

64.7 

156 

27 

704° 

71,000 

51,000 

34.0 

59.3 

137 

25 

Heated  to  815° 

427° 

110,000 

81,000 

19.0 

46.0 

223 

35 

quenched  in 

482° 

103,000 

71,000 

22.5 

54.7 

192 

33 

water 

538° 

95,000 

68,500 

23.5 

61.6 

187 

32 

593° 

89,000 

63,000 

28.5 

63.0 

179 

29 

649 

82,000 

57,500 

30.5 

65.4 

156 

26 

704° 

73,000 

51,000 

34.0 

59.8 

143 

25 

!The  data  for  this  table,  as  well  as  that  for  tables  65,  68,  and  69,  were  supplied 
by  Henry  Wysor,  of  the  Bethlehem  Steel  Company. 


562  TEE  TREATING  OF  STEEL 

SECTION   V. 

CASE    HARDENING. 

The  Process  of  Carburizing  Iron:  It  is  a  well  known  fact  that  if 
a  bar  of  wrought  iron  or  soft  steel  be  heated  to  a  temperature  close  to  or 
above  the  critical  range  in  contact  with  carbonaceous  materials  and  within  a 
suitable  receptacle  from  which  air  is  excluded  after  the  heating  is  started, 
the  bar  of  metal  will  absorb  carbon,  the  amount  so  absorbed  depending 
upon  the  time  the  bar  is  kept  in  contact  with  the  carbon,  the  temperature 
maintained  during  the  operation,  the  nature  of  the  carbonaceous  material, 
and  the  initial  composition  of  the  bar  itself.  This  characteristic  of  iron 
with  respect  to  carbon  was  first  made  use  of  in  the  manufacture  of  steel 
from  wrought  iron  by  the  cementation  process,  then  for  the  surface  car- 
burizingof  armor  plate,  and  finally  for  case  hardening,  or  surf  ace  carburizing, 
smaller  articles.  Essentially,  case  hardening  is  but  a  special  application 
of  the  cementation  process,  in  which  the  articles  treated  are  but  partially 
carburized  and  the  case  extends  but  a  short  distance  from  the  surface, 
leaving  the  central  portions  of  the  articles  unchanged  in  chemical  com- 
position. Thus,  while  the  chief  principle  of  carburizing  iron  has  been 
known  and  made  use  of  for  years,  it  is  only  within  recent  times  that  case 
hardening  has  become  a  process  of  commercial  importance. 

Application  of  Case  Hardening:  The  result  sought,  in  most  cases 
where  case  hardening  is  employed,  is  the  production  of  a  hard,  wear-resisting 
surface  upon  a  tough,  ductile  core.  It  is,  therefore,  applied  to  many  tools, 
to  gears,  to  ball  bearings  and  to  various  parts  of  automobiles,  airplanes, 
bicycles  and  the  like — in  fact,  wherever  a  combination  of  toughness  and 
lightness  with  a  wear-resisting  surface  is  desired.  On  account  of  the  wide 
application  of  the  process  and  the  fact  that  the  art  has  not  yet  reached 
the  stage  of  fullest  development,  a  wide  variation  in  the  methods  of 
applying  the  process  is  to  be  expected.  This  condition  makes  the  subject 
a  difficult  one  to  deal  with  briefly  and  at  the  same  time  satisfactorily. 
In  the  following  paragraphs,  an  attempt  has  been  made  to  give  a  summary 
of  the  facts  as  revealed  by  the  work  of  many  investigators  who  have  pub- 
lished or  otherwise  made  known  the  results  of  their  experiments  and  experi- 
ence. Only  general  features  are  thus  dealt  with,  because  the  working  out 
of  details  is  largely  a  matter  to  be  determined  by  experience. 

The  Two  Periods  of  the  Case  Hardening  Process:  In  order  to 
obtain  the  greatest  benefits  from  case  hardening,  it  is  necessary  that  the 
carburization  be  succeeded  by  proper  heat  treatment,  or  that  the  carburizing 
process  be  considered  as  a  part  of  a  special  heat  treating  process.  The 
chief  factors  that  control  the  carburization  have  already  been  enumerated. 
Since  a  relatively  high  temperature  is  employed  in  the  carburizing  process 
and  the  cooling,  at  the  end  of  the  carburizing  period,  is  usually  slow,  the 
steel,  as  a  whole,  is  in  its  softest  condition,  and  has  a  large  grain  structure. 


CASE  HARDENING  563 


Therefore,  the  heat  treating  part  of  the  process  must  combine  a  grain 
refining  operation  for  low  carbon  steel  with  a  hardening  and- grain  refining 
treatment  for  high  carbon  steels. 

Kinds  of  Steel  Suitable  for  Case  Hardening:  In  general,  the  com- 
position of  the  steel  for  case  hardening  is  limited  by  the  desire  to  eliminate 
any  elements  that  produce  brittleness  in  the  core,  and  also  any  that  tend 
to  retard  the  absorption  of  carbon  by  the  steel.  The  elements  that  may 
be  permitted  and  those  that  should  be  avoided  in  steel  for  case  hardening 
will,  therefore,  be  easily  recognized  after  a  study  of  the  two  succeeding 
chapters  which  are  devoted  to  the  effects  of  the  elements  upon  the  prop- 
erties of  steel.  For  convenience,  however,  a  list  of  the  elements  with  data 
concerning  their  case  hardening  properties  is  given  here. 

Carbon:  Since  the  tendency  of  carbon,  especially  when  present  in 
any  amount  greater  than  .25  per  cent.,  is  to  increase  the  brittleness,  .30 
per  cent,  is  the  limit  to  which  the  carbon  in  steel  for  case  hardening  may 
rise.  Therefore,  the  carbon  content  of  steels  for  this  purpose  ranges  from 
.08  to  .25  per  cent.  For  ordinary  purposes  a  carbon  content  of  .08  to  .15 
per  cent,  is  most  satisfactory.  However,  as  steel  of  this  grade  is  difficult 
to  machine  so  as  to  give  a  smooth  surface,  and  a  fairly  strong  core  is  de- 
sirable for  some  kinds  of  work,  a  carbon  content  of  .15  to  .25  per  cent  is 
frequently  specified.  Needless  to  say,  the  higher  carbon  grade  requires 
more  care  in  treatment  than  the  low  carbon  grade. 

Manganese:  While  manganese  increases  the  ability  of  the  steel  to 
absorb  carbon,  on  account  of  its  tendency  to  make  the  case  brittle  and 
sensitive  to  shock,  the  per  cent,  of  this  element  is  generally  kept  below 
.50,  though  steel  with  a  manganese  content  of  .70  per  cent,  is  sometimes 
employed. 

Silicon:  When  the  silicon  content  is  raised  to  2.0  per  cent.,  the  steel 
refuses  to  absorb  carbon,  hence  the  steel  should  be  kept  as  free  of  this 
element  as  possible.  The  highest  limit  for  silicon  to  give  commercially 
satisfactory  results  is  about  .30  per  cent* 

Phosphorus  and  Sulphur:  The  phosphorus  and  sulphur  content  of 
the  steel  should  be  as  low  as  possible,  not  over  .05  per  cent,  for  each  of 
these  elements. 

Nickel:  Nickel  strengthens  and  toughens  steel,  but  retards  the  car- 
burization  of  the  metal.  The  rate  of  penetration  is  lowered  in  proportion 
to  the  amount  present,  so  that  in  a  steel  with  a  nickel  content  of  5  per  cent., 
the  rate  of  penetration,  using  solid  carburizing  materials,  is  about  half 
that  in  the  plain  low  carbon  low  manganese  steels.  But,  offsetting  this 
disadvantage,  nickel  steels  possess  certain  peculiarities  of  structure  and 
increased  toughness,  which  make  them  desirable  for  carburizing  purposes. 

Vanadium:  This  element  also  lowers  the  rate  of  carbon  penetration, 
but  since  it  is  present  in  very  small  amounts,  its  action  in  this  respect  is 
less  pronounced  than  in  the  case  of  nickel. 


f.64  THE  TREATING  OF  STEEL 

Chromium:  The  low  carbon  chrome  steels,  especially  those  con- 
taining about  0.5  per  cent,  chromium,  are  well  adapted  to  case  hardening, 
for  the  chromium  not  only  increases  the  rate  of  penetration  and  the  con- 
centration of  the  carbon  in  the  case,  but  also  materially  reduces  the  grain 
size.  Furthermore,  this  amount  of  chromium  does  not  harden  the  case 
nor  render  it  brittle  beyond  that  which  would  be  obtained  by  slightly 
increasing  the  carbon  content  of  the  plain  carbon  steel. 

The  Carburizing  Agent:  Many  investigations  have  been  conducted 
to  determine  just  what  the  carburizing  action  is.  Originally,  it  was  held 
that  the  carbon  was  absorbed  directly  at  the  surface  of  the  metal  and 
there  dissolved,  the  dissolved  carbon  being  then  disseminated  towards  the 
interior.  That  dissolved  carbon  may  move  about,  or  diffuse,  within  the 
metal  is  accepted,  but  it  has  been  proved  that  carbon  alone  in  contact  with 
iron  has  only  a  slight  carburizing  action  and  that,  for  commercial  carburi- 
zation,  the  presence  of  carbon  bearing  gases  is  necessary.  By  diffusing  into 
the  steel  where  they  may  react  with  the  iron,  these  gases  act  as  carriers 
of  the  carbon.  The  gases  available  for  this  purpose  are  carbon  monoxide, 
cyanogen,  and  gaseous  hydrocarbons.  Of  these,  carbon  monoxide  and 
cyanogen  bearing  gases  are  the  most  effective,  but  the  former  gives  a  much 
more  uniform  gradation  of  the  carbon  content  from  the  exterior  to  the 
interior  of  the  case,  and  is  to  be  preferred  on  that  account.  The  reaction 
by  which  carburization  is  effected  with  carbon  monoxide  is  generally 
assumed  to  be  the  following:  2  CO+3Fe=Fe3C+CO2. 

Carburizing  Materials:  A  great  number  of  different  carburizing 
materials,  consisting  of  gases,  liquids  and  solids,  have  been  tested  by  the 
many  investigators,  and  of  these,  solids  are  by  far  the  most  convenient  for 
the  purpose  as  well  as  the  most  effective,  when  they  are  of  the  proper  com- 
position. In  the  use  of  solid  carburizers,  the  chief  essentials  to  success  are 
carbon  in  suitable  form,  a  sufficiently  high  and  properly  regulated  temper- 
ature maintained  for  a  proper  length  of  time,  and  reasonable  care  as  to  the 
details  of  preparing  the  carburizer  and  packing  the  articles  therein.  For 
supplying  the  carbon,  many  different  substances  may  be  employed,  such  as 
coke,  wood  charcoal,  sugar  charcoal,  animal  charcoal,  charred  bones, 
charred  leather,  etc.  Coke  and  wood  charcoal  are  not  as  rapid  as  these 
other  forms  of  carbon.  Care  is  required  in  using  coke,  bones,  leather  and 
animal  charcoal  to  guard  against  imparting  phosphorus  and  sulphur  to  the 
metal.  The  material  selected  should  be  ground  or  crushed  to  the  proper 
degree  of  fineness  and  to  a  fairly  uniform  size,  after  which  it  should  be 
sifted  free  of  dust. 

Packing  and  the  Action  of  Charcoal  Carburizer:  Assuming  that 
charcoal  is  selected,  the  article  or  articles  to  be  case  hardened  are  packed 
with  the  carburizer  in  a  hardening  pot  or  box  of  suitable  size  and  shape. 
The  boxes  may  be  of  soft  steel,  wrought  iron  or  cast  iron.  The  walls  should 
be  thin,  about  one-fourth  inch  in  thickness,  and  of  a  size  and  shape  that  will 


CASE  HARDENING  565 


permit  the  rapid  penetration  of  the  heat,  so  that  the  lag  in  temperature  of 
the  central  part  of  the  packed  box  behind  the  furnace  temperature  will  be 
as  small  as  possible.  The  best  shape  is  one  that  conforms  to  that  of  the 
piece  or  pieces  to  be  carburized.  The  article,  or  each  of  the  articles,  in  a 
charge  should  be  placed  so  that  it  will  be  completely  surrounded  by  a 
layer  of  the  carburizing  material,  about  an  inch  in  thickness.  In  case 
it  is  desired  to  carburize  only  certain  parts  of  the  article,  the  parts 
that  are  not  to  be  carburized  may  be  covered  with  asbestos  cement, 
or  slaked  lime  or  fire  clay  in  the  form  of  a  paste.  When  the  packing  has 
been  completed,  the  open  end  of  the  box  is  closed  with  a  neatly  fitting 
lid,  which  is  pressed  down  firmly  against  the  top  layer  of  carburizing 
material  and  fastened  tightly  in  place,  so  that  it  will  permit  no  displacement 
of  the  pack  or  packing  in  handling.  The  small  opening  about  the  edge  of 
the  lid  is  then  luted  with  asbestos  cement,  clay,  or  a  mixture  of  fire  clay 
and  sand;  then,  the  box  is  ready  for  charging.  When  the  contents  of  the 
box  have  reached  a  certain  temperature  in  the  furnace,  the  oxygen  of  the 
air  that  fills  the  interstitial  spaces  of  the  packing  reacts  with  the  carbon, 
giving  carbon  monoxide,  which  in  turn  reacts  with  iron  to  give  iron  carbide 
and  carbon  dioxide  gas,  as  previously  described.  The  iron  carbide,  of 
course,  remains  in  the  metal  to  form  the  case,  while  the  carbon  dioxide 
is  given  off.  When  it  comes  in  contact  with  the  carburizing  material, 
CO  gas  is  again  generated,  thus,  CO2+C=2  CO.  This  CO  then  reacts 
with  iron  as  before.  This  cycle  is  made  again  and  again,  until  the  process 
is  stopped,  or  the  iron  becomes  saturated  with  carbon.  In  the  case  of  bones, 
leather,  and  other  animal  or  vegetable  matter,  other  more  complicated 
reactions,  due  to  cyanogen  and  hydrocarbon  vapors  given  off  by  these 
substances,  occur  in  addition  to  the  simple  reactions  resulting  from  the 
carbon,  as  explained  in  connection  with  the  use  of  charcoal. 

Carburizing  Mixtures  and  Compounds:  These  simple  substances 
may  also  be  used  as  the  base  materials  for  various  carburizing  mixtures 
designed  to  suit  the  conditions  and  the  results  desired.  Thus,  in  the  case 
of  thin  cases,  where  it  is  desired  to  increase  the  speed  or  rate  of  penetration 
and  where  the  forming  of  a  case  of  uniform  thickness  is  essential,  the  follow- 
ing mixtures  have  been  recommended: 

1 .  Powdered  wood  charcoal  with  a  little  heavy  hydrocarbon  oil  added. 

2.  Powdered  wood  charcoal,  leather  charcoal,  and  lampblack  in  the 
proportion  of  5,  2,  and  3  parts,  respectively. 

3.  Powdered  wood  charcoal,  7  parts,  and  animal  charcoal,  3  parts. 

4.  Powdered  wood  charcoal,  charred  horn  and  animal  charcoal,  in 
proportion  of  three  parts  of  the  first  and  two  parts  of  each  of  the  others. 

The  increased  rate  of  carburization  that  may  be  obtained  by  the  use 
of  these  mixtures  is  due  to  the  fact  that  they  give  off  volatile  hydrocarbons 
and  cyanogen  compounds  as  well  as  carbon  monoxide,  and  that  these  com- 
pounds are  capable  of  causing  carburizing  reactions  independent  of  and  in 
addition  to  that  involving  carbon  monoxide. 


566  THE  TREATING  OF  STEEL 

In  addition  to  these,  mixtures  of  wood  charcoal  with  common  salt  or 
with  barium  carbonate  have  been  found  very  efficient  and  desirable  car- 
burizing  materials.  Just  what  part  common  salt  may  play  in  the  process 
is  not  known,  but  the  action  of  barium  carbonate  is  easily  explained.  At 
the  higher  carburizing  temperatures  it  is  decomposed  according  to  the 
following  reaction:  BaCO3=BaO+CO2-  The  CC>2  thus  generated  is 
immediately  reduced  by  the  hot  carbon  to  CO  gas,  each  volume  of  CO2 
giving  two  volumes  of  CO;  thus,  CO2+C=2  CO.  The  net  effect  of  the 
barium  carbonate,  then,  is  to  increase  materially  the  amount  of  the  CO 
available.  By  exposing  the  mixture,  after  use,  to  the  air,  the  barium 
oxide  takes  up  CO2,  forming  barium  carbonate  again,  so  that  with  the  ' 
occasional  addition  of  small  amounts  of  charcoal  the  same  mixture  may  be 
used  repeatedly.  Another  advantage  secured  in  using  the  barium  carbonate- 
charcoal  mixtures  is  that  the  danger  of  contaminating  the  steel  with  sulphur 
is  entirely  avoided,  as  these  materials  may  be  obtained  practically  sulphur 
free.  The  mixture  that  has  been  found  to  give  the  best  results  is  one  com- 
posed of  40  parts  of  the  carbonate  to  60  parts  of  charcoal  by  weight. 

When  it  is  desired  to  obtain  a  thin  case  of  high  carbon  content  in  a 
very  short  interval  of  time,  quick  acting  mixtures  are  used.  The  sub- 
stances employed  in  these  mixtures  are  wood  charcoal,  bituminous  coal, 
saw  dust,  charred  leather,  prussiate  of  potash,  sal  soda  and  common  salt. 
From  these  substances  mixtures  that  will  give  various  speeds  of  carburizing 
may  be  made.  For  example,  a  mixture  of  2  parts  wood  charcoal,  1  part 
salt,  and  3  parts  saw  dust  is  relatively  slow  in  its  action  while  a  mixture 
of  10  parts  charred  leather,  2  parts  prussiate  of  potash  and  10  parts  saw 
dust  is  characterized  as  very  rapid. 

Heating  the  Carburizing  Pack:  For  heating  up  the  charged  carbur- 
izing boxes,  some  form  of  gas  fired  muffle  furnace  is  preferable.  The 
essential  requirements  of  the  furnace  are  that  it  must  be  capable  of  giving 
a  maximum  temperature  of  at  least  1000°  C.,  any  definite  temperature 
lower  than  1000°,  and  also  be  capable  of  maintaining  these  definite  tem- 
peratures uniformly  throughout  the  heating  chamber  for  periods  of  several 
days  at  a  time.  In  order  to  avoid  the  rapid  oxidation  and  consequent 
destruction  of  the  carburizing  boxes,  a  reducing  atmosphere  should  be 
maintained  in  the  heating  chamber,  and  furnaces  constructed  so  as  to  effect 
this  result  are  most  desirable.  The  furnace  should  be  cold,  or  nearly  so, 
when  the  packed  boxes  are  charged,  and  the  heating,  up  to  the  carburizing 
point,  should  be  very  gradual.  The  steel  will  thus  have  time  to  adjust 
itself  to  the  conditions;  the  pack  will  be  uniformly  heated  throughout,  so 
that  carburization  will  begin  in  all  parts  of  the  pack  at  the  same  time; 
and  the  evolution  and  generation  of  gases,  which  begins  at  temperatures 
slightly  below  700°  C.,  will  not  be  too  energetic.  The  temperature  and  the 
length  of  time  for  carburizing  depend  on  the  depth  and  the  carbon  content 
of  the  case  desired,  the  carburizing  material,  and  the  character  of  the  raw 


CASE  HARDENING  567 

iron  or  steel.  In  general,  for  a  given  set  of  materials,  the  higher  the  tem- 
perature and  the  longer  the  time  of  carburizing,  the  greater  will  be  the  depth 
of  the  carburized  zone;  and  when  solid  carburizers  are  used,  the  same  may 
be  said  with  respect  to  the  maximum  carbon  content  or  carbon  concen- 
tration of  the  case.  That  the  carburizing  material  may  affect  the  speed  of 
the  carburization  has  already  been  intimated  in  discussing  carburizing 
mixtures.  A  similar  difference  is  also  found  in  their  action  with  respect  to 
the  concentration  of  the  carbon.  Thus,  while  one  carbunzer  will  give,  for 
example,  a  case  with  a  surface  hardness  corresponding  to  .80%  carbon  at 
870°  C.,  1.05%  carbon  at  900°.  C.,  etc.,  another  will  give  only  a  .70%  case 
at  870°  C.  and  a  .90%  case  at  900°  C.  In  treating  ordinary  carbon  steel, 
a  temperature  between  875°  and  900°  is  considered  best  to  avoid  large  grain 
size  and  obtain  the  most  satisfactory  results.  With  this  temperature 
determined  upon,  the  depth  of  the  case  and  the  concentration  of  the  carbon 
may  be  regulated  by  varying  the  time  of  carburizing  and  the  composition 
of  the  carburizing  material  employed. 

Controlling  the  Temperature:  In  regulating  the  temperature  of  the 
pack  it  should  be  kept  in  mind  that  the  temperature  of  the  furnace  cannot 
be  relied  upon  to  give  the  actual  temperature  of  the  interior  of  the  pack. 
The  temperature  of  the  latter,  during  the  time  it  is  being  brought  to  heat, 
will  tend  to  lag  behind  that  of  the  furnace,  and  after  a  temperature  of  700 °C. 
is  passed  the  chemical  reactions  within  the  pack  itself  may  result  in  the 
liberation  or  absorption  of  a  quantity  of  heat  sufficient  to  maintain  its 
temperature  several  degrees  above  or  below  that  of  the  furnace.  Evidently, 
then,  some  means  of  ascertaining  the  temperature  of  the  interior  of  the  pack 
is  very  desirable.  For  this  purpose  a  pyrometer  of  the  thermo-electric 
type  is  admirably  suited,  because  with  this  instrument  the  hot  junction  of 
the  thermo  couple  may  be  placed  in  the  center  of  the  pack  as  it  is  being 
made  up,  or  inserted  through  a  small  tube  so  placed. 

Removal  of  the  Articles  from  the  Boxes  After  Carburizing:    In 

cases  where  it  is  desired  to  prevent  the  oxidation  of  the  surface  of  the 
articles  treated,  it  is  necessary  either  to  permit  them  to  cool  nearly  to 
atmospheric  temperature  in  the  boxes  or  to  quench  them  by  emptying  the 
entire  contents  of  the  box,  inverted  and  with  its  opening  very  close  to  the 
surface,  into  the  quenching  liquid.  Some  materials  are  quenched  from  the 
carburizing  temperature  for  the  purpose  of  hardening  them,  but  in  order  to 
refine  the  grain,  which  is  coarse,  due  to  the  long  period  of  exposure  to  a 
relatively  high  temperature,  and  secure  the  greatest  toughness  combined 
with  greatest  hardness,  the  carburized  articles  must  be  subjected  to  special 
heat  treating  processes,  in  which  case  the  articles  may  be  removed  from  the 
carburizing  boxes  at  any  convenient  time  and  allowed  to  cool  in  the  air 
to  atmospheric  temperatures  or  at  least  to  a  temperature  that  gives  a 
black  color. 


568  THE  TREATING  OF  STEEL 

Heat  Treatment  of  Case  Hardened  Articles:  The  correct  heat 
treatment  of  case  hardened  articles  involves  a  combination  of  methods 
suitable  to  steels  of  different  carbon  content.  Upon  the  core  of  low  carbon 
content  there  is  superimposed  a  layer  of  high  carbon  steel,  which  may  be 
of  hypo-eutectoid,  eutectoid,  or  hyper-eutectoid  composition,  and  the 
treatments  should  be  varied  to  correspond  to  these  three  different  cases 
and  to  the  temperature  at  which  the  carburization  was  carried  on.  To 
secure  maximum  refinement  of  grain  in  the  core  it  is  necessary  to  heat  the 
steel  just  above  its  Acg  point,  which  for  a  .15%  to  .20%  carbon  core,  is 
a  temperature  near  900°,  and  quench,  preferably,  in  oil.  As  this  temper- 
ature is  far  above  the  Ac  range  of  either  a  hypo-eutectoid  or  eutectoid 
case,  this  treatment  hardens  the  case  but  leaves  its  grain  structure  relatively 
coarse.  Therefore,  the  article  should  be  reheated  to  a  temperature  slightly 
above  the  Ac3-2-±  range  of  the  case  and  again  quenched  in  water  or  oil. 
Finally,  to  prevent  brittleness  in  the  case  and  to  remove  strains,  it  is  desir- 
able to  temper  the  steel  at  once  by  reheating  to  200°  or  over,  depending 
upon  the  hardness  it  is  desired  the  case  shall  retain.  The  temperature 
mentioned  would  relieve  strains  but  would  reduce  the  hardness  very  little, 
if  any.  Hyper-eutectoid  cases  require  that  the  treatment  described  above 
be  modified  to  the  extent  that  either  the  first  reheating  shall  be  above  the 
Accm  range,  or  that  the  article  be  quenched  from  the  carburizing  temper- 
ature, in  order  that  the  excess  cementite  may  be  retained  in  solution.  The 
further  treatment  may  then  be  a  repetition  of  that  for  hypo-eutectoid  cases, 
or  merely  a  quenching  from  above  the  Ac3-2-i  range  (750°  C.).  This  last 
method  leaves  the  core  somewhat  brittle,  due  to  a  large  grain  size,  but 
produces  a  surface  of  exceptional  wear  resisting  properties.  In  any  of  these 
cases,  where  the  carburizing  has  been  carried  on  at  a  high  temperature 
and  has  occupied  a  considerable  period  of  time,  double  quenchings  are 
sometimes  necessary  to  secure  the  best  results. 

Superficial  Hardening:  For  the  most  superficial  hardening  and  at 
the  same  time  the  most  rapid,  such  as  is  sometimes  desirable  for  hardening 
certain  tools,  cyanide  of  potassium  or  prussiate  of  potassium  alone  may  be 
used  in  either  one  of  two  ways.  In  one,  the  salt  is  melted  and  the  article 
to  be  hardened  is  brought  to  the  quenching  temperature  by  immersing  it 
in  the  fused  salt,  held  at  that  temperature  for  a  few  minutes,  the  exact 
time  depending  upon  the  amount  or  extent  of  the  carburization  desired, 
and  then  quenched  as  for  ordinary  hardening,  except  that  lime  water  should 
be  used  to  neutralize  the  poisonous  cyanide.  In  the  other  method,  the 
article  to  be  hardened  is  heated  to  the  h  ardening  temperature  and  is  then 
sprinkled  with  the  dry  salt  or  plunged  into  a  quantity  of  the  dry  salt.  It 
is  then  reheated  to  the  hardening  temperature  and  quenched,  as  in  the 
first  method.  Although  often  spoken  of  as  such,  this  treatment  is  not  a 
true  case  hardening  process. 


INFLUENCE  OF  ELEMENTS  569 


CHAPTER  III. 

CONSTITUENT  ELEMENTS  OF  COMMERCIAL  CARBON  STEEL 

AND  THEIR  INFLUENCE  UPON  IJS 

MECHANICAL  PROPERTIES. 

Introductory:  Needless  to  say  that  a  complete  discussion  of  the 
effects  upon  the  properties  of  steel  of  all  the  elements  that  naturally  may 
be  found  in  it  or  that  may  be  added  to  it  would  be  a  very  lengthy  one, 
indeed.  Even  a  thorough  study  of  the  subject  as  limited  by  the  title  of 
this  chapter  would  involve  an  immense  amount  of  labor  on  the  part  of  the 
writer  and  much  time  on  the  part  of  the  reader  to  peruse  it.  The  most 
that  is  to  be  expected,  therefore,  in  the  following  discourse  is  but  a  brief 
summary  of  the  opinions  of  the  different  authorities  as  presented  in  the 
various  text  books,  the  trade  papers,  and  the  reports  of  conventions,  and 
some  deductions  and  conclusions  arrived  at  through  personal  experience.  In 
examining  the  information  from  these  sources,  the  student  is  confronted 
with  much  difference  of  opinion,  which  often  results  in  much  confusion  of 
thought.  But  a  systematic  search  enables  the  student  to  arrive  at  the 
conclusion  that  certain  elements,  like  manganese,  for  example,  are  bene- 
ficial; others,  like  oxygen,  are  harmful;  some,  like  phosphorus  and  sulphur, 
are  of  doubtful  influence;  while  others  may  be  beneficial  or  harmful,  depend- 
ing upon  conditions.  In  this  regard,  it  is  important  to  note  that  opinion 
at  present  is  changing  with  respect  to  the  influence  of  many  of  the  elements. 
This  is  particularly  true  of  phosphorus  and  sulphur,  both  of  which  were 
recently  held  to  be  injurious  to  steel  under  any  conditions  and  at  all  times. 
Now,  however,  these  elements,  far  from  being  considered  as  foes  to  good 
steel  making,  are,  within  certain  limits,  being  looked  upon  as  harmless  to 
the  steel,  and  even  as  aids  for  certain  purposes.  With  these  things  in 
mind,  an  attempt  has  been  made  here  to  put  down  what  appears  to  be  the 
truth  concerning  these  elements  as  revealed  after  a  study  such  as  that 
suggested  above. 

Properties  of  Iron:  Since  iron  is  the  element  that  forms  the  base 
material  for  the  steel,  the  discussion  of  this  subject  is  naturally  begun 
with  a  consideration  of  the  properties  of  this  element,  though  pure  iron  is 
unknown  commercially.  As  the  physical  and  chemical  properties  of  the 
element  will  be  found  under  the  subjects  of  Physics  and  Chemistry  and 
the  Heat  Treatment  of  Carbon  Steel,  it  is  not  necessary  even  to  tabulate 
them  here.  In  this  connection,  special  emphasis  is  to  be  laid  upon  the 
strength  and  ductility  of  the  element.  Seeing  that  it  is  almost  impossible 


570  INFLUENCE  OF  ELEMENTS 

to  obtain  pure  iron  in  sufficient  quantity  for  testing,  the  determination  of 
these  properties  cannot  be  made  directly.  However,  figures  that  appear 
to  be  as  near  the  true  values  as  it  is  possible  to  get,  have  been  assigned 
for  these  properties  by  calculating  from  results  of  pulling  tests  upon  the 
purest  forms  of  annealed  or  normalized  commercial  soft  steels.  After  making 
what  would  appear  to  be  a  proper  allowance  for  the  influence  of  the  small 
amounts  of  carbon  that  these  steels  contain,  it  has  been  established  that 
pure  iron  has  an  elastic  limit  of  about  20000  pounds,  a  tensile  strength,  or 
maximum  stress,  of  38000  to  40000  pounds,  a  reduction  of  area  of  84%,  and 
an  elongation,  measured  in  8  inches,  of  51%.  From  these  values  it  is  seen 
that  pure  iron  is  a  very  ductile  substance,  but  weak  as  compared  with  steel. 

Effect  of  Carbon :  The  influence  of  carbon  upon  iron  is  so  character- 
istic and  beneficial  that  it  is  employed  as  the  controlling  element  in  regu- 
lating the  physical  properties  of  all  common  steels.  While  this  element  is 
capable  of  changing  most  of  the  physical  properties  of  iron  by  uniting  and 
alloying  with  it,  its  most  important  influence  is  connected  with  the  hard- 
ness, strength,  and  ductility  of  the  metal.  Its  effect  upon  these  properties 
may  be  varied  in  extent  by  heat  treatment,  as  is  fully  explained  in  the 
chapter  on  that  subject.  It  is  to  be  noted  here,  however,  that,  with  respect 
to  its  influence  upon  the  strength  and  ductility  of  naturally  cooled  steel, 
the  average  results  obtained  by  four  eminent  investigators  show  that  for 
each  0.1%  carbon  added  to  steel  up  to  .90%,  these  properties  are  affected 
approximately  as  follows: 

Yield  point  is  raised 3987  pounds  per  sq.  in. 

Maximum  stress  is  raised 9363       "         "        " 

Elongation  is  reduced 4.33% 

Reduction  of  area  is  reduced 7.27% 

Above  1.00%  in  carbon  content,  the  brittleness  of  steel  increases  so 
rapidly,  due  to  the  presence  of  excess  cementite,  that  its  use  is  then  limited 
to  articles,  relatively  few  in  number,  requiring  great  hardness  and  little 
toughness  or  ductility.  Hence,  the  carbon  content  of  commercial  steel  will 
seldom  exceed  1.10%. 

Influence  of  Manganese:  The  chemical  properties  of  manganese, 
which  impart  to  it  the  power  of  combining  with  the  oxygen  of  ferrous-oxide 
and  of  setting  free  the  iron,  make  it  invaluable  as  a  cleansing,  or  deoxidizing 
agent,  and  have  been  referred  to,  time  and  again,  in  describing  the  various 
processes  of  making  steel.  It  is  here  appropriate  to  consider  the  effect  of 
the  manganese  that  remains  in  the  steel  after  deoxidizing.  Of  this  residual 
manganese,  it  may  be  said  that  every  one  is  agreed  that  its  effects,  when 
present  up  to  certain  limits,  varying  with  conditions  and  the  use  to  which 
the  steel  is  to  be  put,  are  wholly  beneficial.  Aside  from  causing  the  steel 
to  roll  and  forge  better,  it  is  a  well  known  fact  that  manganese  adds  some- 
what to  the  tensile  strength,  this  beneficial  effect  depending  upon  the 
carbon  content  as  well  as  that  of  the  manganese.  According  to  H.  H. 


MANGANESE  571 


Campbell1  the  tensile  strength  of  untreated  open  hearth  steel,  containing 
.30%  manganese  and  over,  rises  for  each  increase  of  .01%  in  manganese 
and  with  the  carbon  content  as  shown  in  the  following  table: 

Table  63.  The    Effect  of  Manganese  Upon  the  Tensile  Strength  of  Steel. 

Each  increase  of  .01%  Mn.  above  .30%  or  .40%  raises  the  tensile  strength 
in: 

CARBON  CONTENT           BASIC  OPEN  HEARTH  ACID  OPEN  HEARTH, 

(MN.  ABOVE  .30%)  (MN.  ABOVE  .40%) 

.05                                    110  Ibs.  

.10                                    130    "  80  Ibs. 

.15                                    150    "  120    « 

.20                                    170    "  160    " 

.25                                    190    "  200    " 

.30                                    210    "  240    " 

.35                                    230    "  280    " 

.40                                    250    "  320    " 

When  the  manganese  content  is  less  than  .30%,  this  law  of  increase  is 
disturbed  by  other  influences  of  an  unknown  character,  which  may  even 
cause  a  complete  reversal  of  tendencies  and  the  tensile  strength  to  rise 
when  the  content  falls  below  .30%.  Above  1.00%,  manganese  begins  to 
produce  undue  hardness  and  brittleness  which  becomes  very  marked  as 
the  content  reaches  and  passes  1.50%.  Like  the  tenacity,  these  properties 
are  similarly  affected  by  the  relation  of  the  manganese  to  the  carbon  content. 

Influence  of  Manganese  in  Heat  Treatment:  Relative  to  heat 
treatment,  the  effect  of  manganese  upon  the  heat  treating  qualities  of  the 
steel  are  not  to  be  overlooked.  In  the  case  of  ordinary  open  hearth  steels, 
this  brittleness  of  the  high  manganese  steels  is  associated  with  the  tendency 
of  such  steels  to  crack  just  before  or  during  the  quenching.  Much  care, 
therefore,  must  be  exercised  in  selecting  steel  for  heat  treatment  to  secure 
the  proper  proportion  of  carbon  and  manganese,  for  which  purpose  the 
following  statements  will  be  found  to  apply  in  a  general  way: 

1.  Steels  containing  1.50%  manganese  cannot  be  quenched  in  water, 
whatever  their  carbon  content  may  be,  but  with  the  per  cent,  of  carbon 
no  higher  than  .60  they  may,  depending  on  the  design  of  the  body  and  the 
condition  of  the  steel,  be  quenched  in  oil. 

2.  Steels  containing  1.00%  manganese  and  of  low  or  medium  carbon 
content  may  be  quenched  in  water,  though  the  risk  of  cracking  is  still  great. 

3.  A  manganese  content  of  .40%  or  less  is  required  in  high  carbon 
steels  near  the  eutectoid  (.90%  C.)  composition,  when  such  steels  are  to 
be  hardened  by  quenching  in  water. 

4.  In  hyper-eutectoid  steels,  such  as  high  carbon  tool  steels,   the 
manganese  content  should  not  rise  above  .25%. 

iSee  Manufacture  and  Properties  of  Iron  and  Steel.    Published   by  McGraw 
Hill  Book  Co. 


572  INFLUENCE  OF  ELEMENTS 

5.  Each  0.1%  of  manganese  lowers  the  critical  range  on  heating  by 
about  3°  C. 

6.  According  to  one  authority,  electric  steel  permits  a  higher  content 
of  both  the  carbon  and  the  manganese  in  heat  treating  than  would  be  per- 
missible with  ordinary  open  hearth  steel. 

Influence  of  Manganese  on  Sulphur:  Another  great  benefit  to  be 
gained  from  the  use  of  manganese  is  due  to  its  ability  to  neutralize,  or 
offset,  the  evil  effects  of  sulphur.  Like  oxygen,  this  element  combines 
with  both  iron  and  manganese  to  form  sulphides,  but  in  the  presence  of 
both  elements  and  at  a  high  temperature  it  unites  with  the  latter  in  pref- 
erence to  the  former,  thus  producing  manganese  sulphide,  MnS,  which  is 
practically  harmless  in  steel  for  reasons  that  will  be  explained  shortly. 

Influence  of  Sulphur:  The  effect  of  this  element  upon  the  tenacity 
and  ductility  of  steel,  at  least  up  to  0.1%,  is  so  slight  that  it  may  be  dis- 
regarded. One  investigator  asserts  that  it  accelerates  corrosion  of  the 
steel  that  contains  it.  Its  most  marked  effects,  however,  are  encountered 
in  hot  working,  i.  e.,  rolling  or  forging,  the  steel,  and  they  were  formally 
believed  to  be  always  evil  ones.  That  in  the  form  of  ferrous  sulphide, 
FeS,  it  is  capable  of  doing  great  harm  in  steel  by  causing  redshortness  is 
conceded  by  all,  but  when  neutralized  with  manganese  in  sufficient  amount 
it  may  be  comparatively  harmless,  even  when  present  to  the  extent  of  a 
much  higher  content  than  one-tenth  per  cent. 

Why  Manganese  Neutralizes  the  Effect  of  Sulphur:  The  only  plaus- 
ible explanation  so  far  offered  to  account  for  the  difference  in  the  effect  of 
the  two  sulphides  is  that  the  iron  sulphide  forms  films,  or  cell  walls,  about 
the  grains  of  the  metal,  and  as  this  sulphide  fuses  at  a  red  heat,  these  cell 
walls,  by  becoming  fluid,  interrupt  the  continuity  of  the  mass  and  so  render 
the  steel  hot  short.  Manganese  sulphide,  instead  of  forming  envelopes 
about  the  grains  of  the  metal,  collects,  or  segregates,  into  globules  at  tem- 
peratures near  that  of  the  metal  on  solidifying,  upon  which  the  main  body 
of  metal  then  contracts.  Manganese  sulphide  has  a  much  higher  fusion 
point  than  ferrous  sulphide,  hence  does  not  melt  at  a  rolling  heat,  but 
becomes  merely  plastic  like  the  rest  of  the  metal.  In  this  form,  it  is  rolled 
into  fibers,  which  give  to  the  steel,  when  present  in  sufficiently  large  quan- 
tities, a  fibrous  structure  similar  to  that  of  wrought  iron.  In  order  to 
get  the  full  benefit  of  the  manganese,  it  is  necessary  that  it  should  be  present 
in  the  steel  to  the  extent  of  about  three  times  the  theoretical  amount 
required  for  the  formation  of  the  sulphide.  Roughly,  this  means  that  the 
per  cent,  of  manganese  should  be  five  times  that  of  the  sulphur. 

Uses  for  Sulphur  in  Steel:  This  fibrous  structure  of  high  sulphur 
steel  is  made  use  of  in  the  manufacture  of  free  cutting  steel,  like  screw 
stock,  for  example,  because  the  free  cutting  properties  of  this  steel  are 
undoubtedly  due  to  its  fibrous  structure.  Thus,  in  this  case,  at  least, 


SULPHUR  AND  PHOSPHORUS  573 

sulphur  is  to  be  regarded  as  a  friend  rather  than  as  a  foe.  In  this  con- 
nection, it  should  be  observed  that  experiments  conducted  during  1914  and 
1915  in  both  this  country  and  England  tend  to  show  that  sulphur,  when 
accompanied  with  a  sufficient  amount  of  manganese,  is  not  such  an  enemy 
as  it  is  sometimes  supposed  to  be.  Extensive  investigations  by  our  own 
research  department  have  shown  that  there  is  practically  no  difference  in 
the  rolling,  forging  or  welding  qualities,  nor  in  the  physical  properties,  of 
steels  containing  from  .030%  to  .120%  sulphur.  It  is  interesting  to  consider 
how  the  unfavorable  attitude  toward  sulphur  came  about.  Up  to  within 
the  present. decade,  most  of  the  steel  produced  in  this  country  was  made 
by  the  acid  Bessemer  process  in  which  the  sulphur  content  would  often 
range  from  .070%  to  .100%.  Yet  there  was  no  complaint  about  this  steel, 
and  that  it  gave  excellent  service  for  nearly  all  purposes  that  steel  is  used 
cannot  be  denied.  But  with  the  advent  of  basic  steel,  the  notion  became 
prevalent,  through  academic  discussions  to  explain  why  this  steel  should 
be  better  than  Bessemer,  that  even  a  small  quantity  of  sulphur  was  harmful 
to  the  steel;  and  consumers,  also,  naturally  insisted  on  placing  the  limit  for 
sulphur  at  the  lowest  possible  figure,  under  .040  per  cent,  or  even  under  .030 
per  cent.,  in  order  to  secure  the  better  steel.  Evidently,  however,  such  an 
attitude  should  be  corrected  now,  for  economic  reasons,  if  no  other.  In 
view  of  the  fact  that  it  is  becoming  increasingly  difficult  to  keep  the  sulphur 
content  below  .040%,  it  seems  ridiculous  to  insist  upon  so  low  a  limit, 
when  the  evidence  points  so  strongly  to  .100%  as  a  limit  that  may  be  made 
to  serve  as  well,  for  many  purposes,  at  least.  As  most  basic  steel  made  in 
this  country  appears  to  tend  naturally  toward  a  sulphur  content  of  from 
.050%  to  .060%,  even  raising  the  limit  to  .080%  would  result  in  a  great 
saving. 

Influence  of  Phosphorus:  Phosphorus  is  another  element  that  has 
been  painted  a  little  blacker,  perhaps,  than  it  should.  It  has  been 
everywhere  charged  with  producing  cold  shortness,  or  brittleness  when 
cold,  but  experiments  and  tests  conducted  by  our  research  department, 
during  the  first  half  of  the  year  1917,  seem  to  indicate  that  up  to  .10%  at 
least,  phosphorus  does  not  produce  brittleness  in  the  metal  to  a  degree  that 
is  noticeably  harmful.  In  these  experiments,  steel  with  phosphorus  con- 
tents ranging  from  .018%  to  .110%  were  subjected  to  severe  cold  bending, 
stamping  and  pressing  tests  that  steel  is  called  upon  to  withstand  in 
shaping,  with  the  result  that  the  higher  phosphorus  steels  stood  up  under 
the  tests  as  well  as  the  low  phosphorus  grades,  otherwise  of  identical  com- 
position. That  it  does  increase  the  hardness  and  tensile  strength  of  the 
steel,  causing  at  the  same  time  a  proportionate  reduction  in  the  ductility, 
is  well  established  as  a  fact.  •  In  this  respect  it  is  very  similar  to  carbon. 
Some  authorities  claim  that  it  increases  the  tensile  strength  a  little  more 
than  carbon  with  a  less  reduction  in  the  ductility;  others  say  that  its  effect 
is  practically  the  same  as  carbon  except  that  it  increases  the  brittleness 
a  little  more.  Campbell  claims  that  the  tensile  strength  of  basic  steel  is 


574  INFLUENCE  OF  ELEMENTS 

increased  1000  pounds  for  each  increase  of  .01%  of  phosphorus.  It,  also, 
benefits  the  wearing  properties  of  the  steel  in  much  the  same  way  that 
carbon  does.  In  low  carbon  steels,  it  is  used  in  many  cases  with  entirely 
beneficial  results.  Thus,  it  is  useful  in  sheet  bar,  as  it  is  claimed  that  it 
prevents  the  sheets  from  sticking  together  in  the  pack  during  the  rolling. 

The  Two  Evils  of  Phosphorus:  However,  it  is  not  to  be  inferred 
that  the  indiscriminate  use  of  high  phosphorus  steel  is  advocated,  because 
it  has,  according  to  Howe,  Harbord  and  others,  at  least  two  evil  tendencies 
that  make  it  a  dangerous  element  in  steels  for  certain  purposes.  Speaking 
of  these  tendencies,  Harbord  states  that,  of  all  the  impurities  usually  present 
in  steel,  practical  experience  has  established  the  fact  that  phosphorus  is  the 
one  that  most  prejudicially  influences  the  physical  properties  of  the  metal 
by  producing  brittleness  under  shock,  and  hence  for  practical  commercial 
purposes,  phosphorus  in  steel  should  not  exceed  .080%.  Again,  Howe 
maintains  that  while  phosphorus  sometimes  affects  iron  but  slightly,  at 
other  times,  under  apparently  similar  conditions,  it  affects  it  profoundly. 
In  view  of  this  fact,  which  may  be  called  the  treacherousness  of  phosphoretic 
steel,  it  is  difficult  to  define  a  limit  for  the  maximum  content  of  phosphorus 
which  can  be  safely  allowed  in  steel,  but  reasoning  that  the  lower  this  is, 
the  safer  the  material,  many  would  insist  upon  a  very  low  limit.  That 
this  limit  may  be  unreasonably  low  is  illustrated  in  the  case  of  structural 
steel.  Many  users  of  this  material  refuse  to  accept  any  steel  that  contains 
a  higher  percentage  of  this  element  than  .04%.  Yet  a  class  of  material 
subjected  to  much  more  severe  usage  in  service,  namely,  railroad  rails  made 
by  the  Bessemer  process,  is  permitted  to  contain  as  much^as  .110%  phos- 
phorus. Furthermore,  while  structural  material  is  subjected  to  static 
stresses  mainly,  a  class  of  stress  that  phosphoretic  steel  is  most  capable 
of  resisting,  rails  are  required  to  withstand  shocks  and  impacts,  which 
the  evidence  shows,  high  phosphorus  steels  should  be  least  capable  of 
resisting. 

Influence  of  Silicon:  Apparently  owing  to  the  fact  that  all  but 
traces  of  silicon  may  be  removed  in  any  and  all  of  the  processes  for  manu- 
facturing steel,  the  attention  of  investigators  has  not  been  so  universally 
directed  to  the  effects  of  this  element  on  steel  as  in  the  case  of  the  other 
impurities.  Besides,  whatever  evidence  may  be  collected  will  be  found  to 
vary  somewhat.  Thus,  while  certain  English  investigators  found  that 
steels  containing  as  much  as  2.00%  silicon,  a  content  much  higher  than 
any  employed  in  ordinary  carbon  steel,  suffered  a  marked  reduction  in 
ductility,  others  maintained  that  the  ductility  is  not  markedly  affected  up 
to  a  content  of  .70%.  All  agreed  that  the -tensile  strength  is  increased, 
and  some  maintain  that  small  percentages  of  silicon  increased  the  resistance 
of  the  steel  to  shock.  In  short,  it  is  generally  accepted  by  all  practical 
steel  men  that  silicon  up  to  .75%  is  beneficial,  that  it  increases  the  yield 
point  and  tensile  strength  but  does  not  materially  impair  the  ductility. 


SILICON  AND  OXYGEN  575 

This  statement  is  in  accord  with  the  experience  of  our  own  Company,  who 
found,  for  example,  that  in  a  certain  specification  calling  for  a  tensile  strength 
of  80,000  pounds  with  an  elongation  of  20%  in  eight  inches,  requirements 
that  cannot  be  approached  in  plain  untreated  carbon  steel,  very  satisfactory 
results  were  obtained  by  the  addition  of  .50%  silicon.  Like  manganese, 
silicon  is  a  wonderful  deoxidizer,  or  cleanser,  of  steel,  and  it  is  possible  that 
the  improvement  in  the  quality  of  steel,  and  of  basic  steel  in  particular, 
which  the  addition  of  small  quantities  of  the  element  produce,  is  due  rather 
to  this  property  than  to  any  influence  the  residual  silicon  in  the  steel  may 
have.  Spring  steel  with  the  silicon  ranging  from  .25%  to  .35%  has  greater 
resiliency  than  steels  of  lower  silicon  content,  and  without  increased  brittle- 
ness.  In  steel  castings  it  is  especially  beneficial,  as  it  tends  to  prevent 
blow  holes  and  thus  promotes  soundness.  In  steels  intended  to  be  case 
hardened,  silicon  is  an  objectionable  element,  as  it  retards  the  absorption 
of  carbon.  Therefore,  in  such  steels  the  silicon  content  should  be  low,  as 
the  retarding  effect  begins  at  about  .04  per  cent.  In  sheet  bar,  silicon  is 
like  phosphorus  in  that  it  tends  to  prevent  the  sheets  in  a  pack  from 
sticking  together.  For  this  purpose  .06  per  cent,  is  sufficient. 

The  Influence  of  Oxygen  in  steel  has  been  thoroughly  discussed  and 
emphasized  in  connection  with  the  various  methods  for  manufacturing  steel. 
It  may,  however,  again  be  pointed  out  that  its  effects  are  all  evil  ones, 
causing  both  red  shortness  and  cold  shortness  in  steel,  and  that  when 
present  even  in  so  small  amounts  as  .03%  it  shows  a  marked  tendency  to 
produce  brittleness  under  shock.  The  amount  of  oxygen  steel  is  capable 
of  retaining  is  small.  That  retained  even  by  over-blown  Bessemer  steel 
without  deoxidizing  is  less  than  .15%. 

Combined  Effect  of  the  Elements  on  Tensile  Strength  of  Steel: 

These  elements,  iron,  carbon,  manganese,  sulphur,  phosphorus,  silicon  and 
oxygen,  are  the  ones  found  in  all  commercial  grades  of  steel.  Having 
discussed  their  effects  separately,  it  may  now  be  advantageous  to  consider 
their  combined  effect  upon  the  metal.  Of  these  elements  only  oxygen  is 
to  be  looked  upon  as  being  always  an  enemy.  The  influence  of  manganese 
in  steels  that  are  not  to  be  heat  treated  is  always  good,  as  is  also  that  of 
silicon  in  small  amounts.  The  tensile  strength  is  raised  by  carbon,  man- 
ganese, phosphorus,  and  silicon,  while  the  ductility  is  decreased  by  carbon, 
manganese,  and  phosphorus.  According  to  H.  H.  Campbell  the  influence 
of  these  elements  varies  in  the  different  kinds  of  steels;  and  for  the  two 
kinds  of  open  hearth  steels  in  their  natural  state,  that  is,  without  any  heat 
treatment,  he  sums  up  the  combined  effect  of  carbon,  phosphorus  and 
manganese  on  the  tensile  strength  to  be  approximately  as  given  in  the 
following  formulas: 

First  Method  (of  Least  Squares) : 

A.  Acid  Steel  38600+1210  C+890  P+R=Ultimate  Strength. 

B.  Basic  Steel  37430+950  C+85  Mn+1050  P+R=Ultimate  Strength. 


576  INFLUENCE  OF  ELEMENTS 

Second  Method  (by  Plotting) : 

C.  Acid  Steel  40000+1000  C+1000  P+X  Mn+R=Ultimate  Strength. 

D.  Basic  Steel  41500+770  C+1000  P+Y  Mn+R=Ultimate  Strength. 

In  these  formulas  38600,  37430,  40000  and  41500  represents  the  initial 
strength  of  pure  iron;  C,  P,  Mn,  stand  for  carbon,  phosphorus  and  manganese 
expressed  in  hundredths  of  one  per  cent.,  respectively;  X  and  Y  represent 
variables  changing  with  the  carbon  content  as  given  under  the  heading, 
Influence  of  Manganese;  and  R  is  a  factor  that  depends  on  the  finishing 
temperature,  and  may  be  either  plus  or  minus. 

For  low  carbon  plain  basic  steel,  such  as  that  used  for  plates  and 
structural  shapes,  rolled  at  the  ordinary  temperature  for  hot  rolling,  the 
following  simple  formula  is  used  by  many  inspectors: 

T  (Ultimate  Strength)=39000+950  C+1050  P+85  Mn. 
The  symbols  in  this  formula  have  the  same  significance  as  the  same 
symbols  in  Campbell's  formulas. 

The  Influence  of  Copper  upon  the  mechanical  properties  of  steel, 
when  present  in  small  amounts,  say  up  to  .50%,  is  not  very  pronounced. 
In  terms  of  tenths  of  one  per  cent.,  the  effect  of  copper  as  determined  by 
several  different  investigators  is  about  as  follows:  The  yield  point  is 
increased  1800  pounds  in  steels  of  low  carbon,  and  720  pounds  in  those  of 
medium  carbon  content;  the  maximum  stress,  or  ultimate  strength,  is 
increased  1200  pounds  for  low  carbon,  and  600  pounds  for  medium;  the 
elongation  is  decreased  .75%  for  low  carbon,  and  .25%  for  medium;  the 
reduction  of  area  is  decreased  .45%  for  low  carbon,  and  .50%  for  medium. 
From  these  results  it  is  to  be  decided  that  the  effect  of  small  percentages 
of  copper  is  slight,  and  what  effect  it  has  is  beneficial.  This  declaration 
agrees,  also,  with  the  verdict  of  the  American  Society  for  Testing  Materials. 
For  years  copper  was  looked  upon  as  being  very  injurious  to  the  steel,  it 
being  charged  with  making  the  steel  red-short  and  unweldable.  However, 
as  early  as  1899  A.  L.  Colby  made  an  extensive  series  of  investigations  to 
determine  what  really  were  the  effects  of  small  percentages  of  copper  upon 
the  physical  properties  of  the  steel.  Briefly,  these  investigations  and  the 
results  obtained  were  as  follows:  A  steel  shaft  15  inches  in  diameter  by 
fourteen  feet  long,  corresponding  in  composition  with  the  propeller  shafts 
adopted  by  the  U.  S.  Navy  Board,  but  containing  also  .565%  of  copper, 
was  forged  without  difficulty.  Test  specimens  were  doubled  flat  in  the 
cold  without  showing  cracks  or  flaws,  and  the  tensile  strength  and  ductility 
were  well  up  to  requirements  of  the  Navy.  In  another  series  of  tests  the 
material,  containing  .553%  copper,  was  forged  into  a  gun-tube,  and  satisfied 
all  the  requirements  for  the  U.  S.  Navy  for  a  6  inch  gun.  Mild  steel  in  the 
form  of  ship-plates,  containing  .573%  copper,  passed  all  the  tests  required, 
except  a  quarter  inch  plate  which  was  rolled  too  cold.  The  bending  and 
quenching  tests  of  the  bars  cut  longitudinally  were  also  satisfactory,  but 


COPPER,  TIN,  ARSENIC  577 

some,  bent  transversely  to  the  direction  of  rolling,  developed  cracks.  The 
material  could  be  successfully  welded,  only  one  of  the  specimens  tested 
breaking  at  the  weld,  and  even  then  the  breaking  load  was  61,630  pounds 
per  square  inch.  Flanged  cold,  the  material  gave  excellent  results,  and 
though  most  severely  tested,  developed  neither  defects  nor  flaws.  Other 
investigations  were  directed  to  merchant  bars,  rails,  and  nickel  steel  all 
containing  copper,  and  in  no  case  was  there  any  evidence  of  red-shortness, 
although  the  copper  ranged  from  .089%  to  .486%.  Colby's  conclusions 
were  that  a  good  steel  may  contain  as  much  as  1%  of  copper  without  suffer- 
ing, provided  that  the  sulphur  content  is  not  also  high,  in  which  case  the 
metal  is  likely  to  crack  in  rolling. 

Even  small  amounts  of  copper  in  steel  causes  the  latter  to  resist  cor- 
rosion by  acids  much  better  than  steels  that  do  not  contain  it.  The 
research  department  of  the  American  Sheet  and  Tin  Plate  Company  has 
shown  that  .15%  to  .25%  of  copper  in  steel  sheets  of  heavy  gauge  practically 
preserves  them  from  general  corrosion,  and  that  the  resistance  to  corrosion 
begins  to  be  manifested  by  the  steel  with  the  copper  content  as  low  as 
.03%.  While  copper  compounds  occur  in  many  iron  ores,  only  traces,  if 
any,  are  to  be  found  in  the  Lake  Superior  Ores.  Hence  steels  made  from 
these  ores  are  practically  copper  free,  except  in  cases  where  it  is  added  to 
produce  the  non-corroding  steels.  Occasionally,  however,  whether  intro- 
duced through  accident  or  from  the  ore,  steels  will  be  found  to  contain 
copper  to  the  small  amount  of  .01%  to  .02%. 

Influence  of  Tin:  While  this  element  is  not  found  in  any  of  the  iron 
ores,  the  use  of  detinned  scrap  may  result  in  its  introduction  into  the  steel 
during  the  process  of  manufacture.  Hence,  the  effects  of  small  quantities 
of  tin  in  steel  are  not  to  be  overlooked,  but  unfortunately  this  matter  does 
not  appear  to  have  been  very  thoroughly  investigated.  What  work  has 
been  done  shows  that  tin  forms  an  alloy  or  a  compound  with  iron,  which 
has  the  property  of  making  the  steel  very  hard  at  rolling  temperature. 
Thus,  at  one  steel  works  it  was  impossible  to  roll  a  heat  of  steel  into  which 
there,  had  accidently  been  introduced  tin  to  the  extent  of  .75%.  Tin  in 
steel  increases  the  yield  point  and  the  ultimate  strength  of  the  metal,  but 
to  a  less  degree  than  carbon  or  phosphorus.  So  far  as  they  have  gone, 
investigations  appear  to  indicate  that  .05%  tin  in  steel  would  have  little 
influence  upon  its  mechanical  or  physical  properties,  but  that  larger  quan- 
tities must  be  avoided. 

Influence  of  Arsenic:  This  element  does  not  occur  in  any  of  the  iron 
ores  from  the  Lake  Superior  region,  and  is,  therefore,  never  found  in  steels 
made  from  these  ores.  When  present,  however,  in  small  amounts,  unless 
special  precautions  are  taken  in  making  an  analysis  of  the  steel,  it  is  reported 
as  phosphorus.  Small  amounts  of  arsenic  do  not  affect  the  physical  prop- 
erties of  steel;  above  .20%  its  effect  is  similar  to  that  of  phosphorus,  causing 
cold  shortness. 


578  ALLOY  STEELS 


CHAPTER  IV. 

ALLOY  STEELS. 

SECTION   I. 

INTRODUCTORY. 

Definitions:  So  many  different  elements  may  occur  naturally  in 
steel,  or  be  added  to  it,  in  such  varying  amounts  with  corresponding  vari- 
ations in  effects,  that  it  is  a  difficult  matter  to  determine  just  what  con- 
stitutes an  alloy  steel  even  from  the  standpoint  of  chemical  composition 
alone,  When  it  is  further  considered  that  the  different  methods  of  manu- 
facture also  exert  their  influence,  and  that  certain  elements  may  be  added 
or  allowed  to  remain  for  widely  different  reasons,  the  difficulty  of  wording 
concisely  an  adequate  definition  becomes  more  apparent.  The  definition 
adopted  by  the  International  Association  for  Testing  Materials  is  as  follows: 
"Alloy  steel  is  steel  which  owes  its  distinctive  properties  chiefly  to  some 
element  or  elements  other  than  carbon,  or  jointly  to  such  other  elements 
and  carbon.  Some  of  the  alloy  steels  necessarily  contain  an  important 
percentage  of  carbon,  even  as  much  as  1.25%.  There  is  no  agreement  as 
to  where  the  line  between  alloy  steel  and  carbon  steel  shall  be  drawn." 
In  this  connection  it  is  well  to  note  that  elements  other  than  carbon  are 
always  to  be  desired  in  steel  of  commercial  grade,  at  least.  Such  elements 
may  be  added  or  permitted  to  remain  for  three  distinct  reasons,  namely, 
(1)  to  correct  or  prevent  defects  that  otherwise  would  be  liable  to  occur 
in  the  final  product;  (2)  to  impart  to  the  steel  some  distinctive  property 
or  to  improve  materially  its  natural  properties;  (3)  to  form  alloys  for  the 
purpose  of  experimentation  and  investigation.  The  addition  of  silicon  and 
manganese  to  steel  illustrates  the  point  it  is  desired  to  explain.  In  ordinary 
practice  small  amounts  of  these  elements  are  added  to  deoxidize  the  steel, 
and  incidentally  the  small  amounts  that  remain  in  the  metal  may  improve 
its  properties.  Large  amounts  of  these  elements,  1.50%  to  3.50%  in  the 
case  of  silicon,  and  11%  to  14%  in  the  case  of  manganese,  may  be  added 
to  impart  properties  to  the  steel  that  are  distinctive  and  useful.  Other 
proportions  may  be  used,  of  course,  which  result  in  imparting  properties 
that,  while  they  are  distinctive,  are  not  useful,  and  so  these  iron  alloys 
have  only  a  scientific  value.  With  these  facts  in  mind,  we  agree  with 
Henry  D.  Hibbard  of  the  Bureau  of  Mines1  who  suggested  the  following 
definitions: 

iSee  Manufacture  and  Uses  of  Alloy  Steels.  Bureau  of  Mines  Bulletin  100. 


ALLOY  STEELS  579 


"Simple  steel,  which  is  often  called  carbon  steel  (or  plain  steel), 
consists  chiefly  of  iron,  carbon,  and  manganese.  Other  elements  are  always 
present,  but  are  not  essential  to  the  formation  of  the  steel,  and  the  content 
of  carbon  or  manganese,  or  both,  may  be  very  small." 

"Alloy  steel  is  steel  that  contains  one  or  more  elements  other  than 
carbon  in  sufficient  proportion  to  modify  or  improve  substantially  and 
positively  some  of  its  useful  properties."  These  steels,  since  they  contain 
a  special  element,  are  sometimes  called  special  steels. 

"Alloy-treated  steel  is  simple  steel  to  which  one  or  more  alloying 
elements  have  been  added  for  curative  purposes,  but  in  which  the  excess 
of  the  element  or  elements  is  not  enough  to  make  it  an  alloy  steel." 

All  the  alloy  steels  manufactured  by  The  Carnegie  Steel  Co.  are  made 
either  in  the  open  hearth  or  the  electric  furnace,  and  the  alloying  elements 
chiefly  employed  are  nickel,  chromium  and  vanadium.  While  a  large  tonnage 
of  steel,  containing  slightly  higher  percentages  of  copper,  silicon  or  manganese 
than  that  prescribed  by  ordinary  practice  for  carbon  steels,  is  made,  these 
elements  in  such  small  quantities  are  not  to  be  considered  as  alloys  but 
rather  as  curative  or  intensifying  elements.  A  definition  that  would  agree 
with  the  customs  of  this  company,  then,  would  appear  to  be  the  following: 
An  alloy  steel  is  steel,  made  by  the  open-hearth  or  the  electric  process, 
which  contains,  in  addition  to  carbon,  some  element  or  elements  added 
with  the  object  of  modifying  and  substantially  improving  its  mechanical 
properties  in  such  a  way  as  to  make  it  more  suitable  for  the  purpose  for 
which  it  is  intended.  This  definition  does  not  include  the  addition  of 
copper  for  obtaining  non-corrosive  steel,  a  chemical  property,  nor  the 
addition  of  small  amounts  of  phosphorus  to  basic  steel  for  sheet  bar,  nor 
the  sulphur  in  screw  stock,  nor  manganese  and  silicon  added  for  curative 
purposes. 

Carnegie  Types  and  Grades:  To  illustrate  the  importance  of  the 
elements  mentioned  above  as  being  the  ones  chiefly  employed  in  alloy 
steels,  the  types  and  grades  of  commercial  alloy  steels  manufactured  by 
the  open-hearth  process  and  fixed  in  1919  as  standards  by  the  Carnegie 
Steel  Company  may  be  cited.  They  are  as  shown  in  table  63: 

These  types  and  grades  are  subject  to  change,  of  course,  and  except 
from  the  standpoint  of  tonnage  represent  only  a  small  part  of  the  whole 
field  of  alloy  steels.  They  are,  however,  representative  of  the  steels  made 
from  the  three  alloying  elements  that,  up  to  the  present  time,  have  been 
found  to  be  of  greatest  value  commercially,  namely,  nickel,  chromium, 
and  vanadium.  Since  it  is  necessary  to  limit  the  scope  of  this  chapter  in 
some  way,  it  seems  appropriate  to  confine  it  to  a  discussion  of  the  influence 
of  these  elements  upon  steel  and  of  the  general  characteristics  of  the  steels 
represented  by  the  types  given  in  this  table. 


580  ALLOY  STEELS 


Table  64.     Carnegie  Standard  Open  Hearth  Alloy  Steels. 
Nickel  Steel.  Low  Nickel-Chrome  Steel. 

Carbon 10  to    .50%    Carbon 15  to    .45% 

Manganese 50  to    .80        Manganese 50  to    .80 

Phosphorus  not  over. .   .04  Phosphorus  not  over. .   .04 

Sulphur  not  over 045  Sulphur  not  over 045 

Nickel 3.25  to  3.75        Nickel 1.00  to  1.50 

Chromium 45  to    .75 

Chrome  Steel.  Chrome- Vanadium  Steel. 

Carbon 15  to   .70        Carbon 15  to    .55 

Manganese 25  to    .50        Manganese 50  to    .80 

Phosphorus  not  over. .   .04  Phosphorus  not  over. .   .04 

Sulphur  not  over 045  Sulphur  not  over 04 

Chromium 60  to    .90        Silicon  not  over 20 

Chromium 80  to  1.10 

Vanadium  not  under ..   .15 

Chrome-Vanadium  Spring  Steel.  Special  Low  Chrome  Spring  Steel. 

Carbon.45to.55,.50to.60,  .55to.65%  Carbon 80  to  .95% 

Manganese 80  to  1.00  Manganese 30  to   .50 

Phosphorus  not  over 04  Phosphorus  not  over.    .04 

Sulphur  not  over 05  Sulphur  not  over 05 

Silicon  not  over 20  Silicon  not  over 20 

Chromium 1.00  to  1.25  Chromium 20  to  .40 

Vanadium  not  under 15 


SECTION   II. 

NICKEL   STEEL. 

Manufacture  of  Simple  Nickel  Steel:  Nickel  steel,  said  to  have 
been  used  for  the  first  time  in  1888,  may  be  made  by  any  of  the  various 
processes  for  the  manufacture  of  steel,  but  the  greater  portion  is  produced 
by  the  open-hearth  process.  At  the  steel-melting  temperature  nickel  is 
chemically  negative  to  iron,  which  is  capable  of  reducing  its  oxides  and 
preventing  its  oxidation,  even  when  the  bath  is  a  highly  oxidizing  one. 
Nickel  may,  therefore,  be  added  to  the  bath  at  any  time  practically  withoui 
any  loss  or  waste,  but  its  addition  is  usually  made  just  long  enough  before 
tapping  to  enable  it  to  become  properly  diffused.  For  the  same  reason 
nickel  cannot  deoxidize  iron,  neither  will  it  decompose  carbon  monoxide 
nor  hold  other  gases  in  solution,  though  it  is  said  to  prevent,  or  hinder  in 
a  measure,  the  segregation  of  carbon  and  the  other  metalloids.  It  is  not 
used,  then,  for  a  curative  agent,  but  only  for  its  beneficial  effect  upon  the 
physical  properties  of  the  steel,  for  which  purpose  it  is  preeminently  a 
strength  giving  element. 


NICKEL  STEELS  581 


The  Different  Nickel  Steels  and  Their  General  Characteristics: 

The  nickel  content  of  the  useful  nickel  steels  varies  from  2%  to  46%,  which 
is  a  wider  range  than  that  covered  by  any  other  alloying  element.  Below 
2%  the  benefits  derived  from  its  addition  alone  to  steel  are  very  slight 
and  are  not  worth  the  extra  cost.  The  great  bulk  of  simple  nickel  steel, 
containing  from  two  to  four  per  cent,  nickel,  is  used  for  structural  purposes, 
such  as  bridges,  gun  forgings,  machine  parts,  engines,  large  dynamos,  steel 
rolls,  and  various  parts  of  automobiles,  because  of  the  superior  mechanical 
properties  imparted  by  the  metal  when  added  in  these  amounts.  Thus, 
for  each  1%  of  nickel  added  above  2%  and  up  to  4.00%  an  increase  of 
approximately  6000  pounds  in  the  tensile  strength  of  this  steel  over  the 
carbon  steel  is  noted,  while  only  a  slight  decrease,  if  any,  in  the  ductility 
occurs,  and  all  this  improvement  is  secured  without  any  heat  treatment 
whatever.  The  best  results,  costs  and  benefits  considered,  appear  to  be 
obtained  when  the  nickel  content  is  between  3  and  4  per  cent.,  the  content 
aimed  at  for  structural  purposes  being  3.25%  to  3.50%.  This  steel  also 
resists  rusting  and  abrasion  better  than  the  plain  carbon  steels.  Nickel 
steel  of  this  grade  lends  itself  well  to  heat  treatment,  and  may  also  be  used 
for  case  hardening,  the  only  objection  to  its  use  for  this  purpose  being  the 
slight  tendency  of  the  nickel  to  retard  the  rate  of  penetration  of  the  carbon. 
When  the  nickel  content  is  raised  above  5%,  the  metal  becomes  very  hard, 
is  difficult  to  work  either  hot  or  cold,  and  is  rolled  only  by  taking  the  greatest 
care.  It  is  in  demand  where  great  resistance  to  shock  is  a  prime  quality, 
such  as  shield  plates  for  protecting  the  ammunition  of  field  artillery  and 
the  men  serving  the  guns  from  rifle  fire.  Up  to  8%,  nickel  increases  the 
hardness  of  the  steel  to  which  it  is  added,  but  leaves  the  metal  still  amenable 
to  heat  treating.  Steels  containing  10%  or  more  of  nickel  cannot  be 
hardened  by  quenching,  but  become  softer  after  being  subjected  to  this 
heat  treating  operation.  In  1914  a  new  alloy  steel,  containing  13%  nickel 
and  .55%  carbon,  was  discovered  by  Arnold  and  Read.  It  is  so  hard  that 
it  cannot  be  machined  or  drilled,  has  a  yield  point  of  134000  pounds,  a 
tensile  strength  of  195000  pounds,  and  an  elongation  of  12%  in  two  inches. 
Before  this  discovery,  15%  nickel  steel,  tensile  strength  about  170000  pounds, 
was  thought  to  be  the  strongest  one  of  the  series.  This  steel  has  been  employed 
occasionally  for  shafting.  Nickel  steel  containing  22%  nickel  is  used  when 
resistance  to  rusting  is  the  prime  consideration.  Thus,  it  was  employed 
in  the  valve  stems  of  the  salt  water  fire  protective  system  installed  by  the 
city  of  New  York,  and  in  similarly  exposed  parts  of  the  pumps  used  in  the 
drainage  system  for  the  city  of  New  Orleans.  It  is  also  said  to  be  suitable 
for  the  spark  poles  in  spark  plugs  for  internal  combustion  engines.  24% 
to  32%  nickel  steel  is  used  for  electrical  resistance,  such  as  those  employed 
in  irons,  toasters,  and  other  household  heaters.  Nickel  steels  with  a  nickel 
content  of  about  24%  are  non-magnetic.  36%  nickel  steel  is  characterized 
by  an  extremely  low  coefficient  of  expansion,  hence  is  used  in  balance  wheels 
of  watches,  the  pendulums  of  clocks,  etc.,  in  order  to  dispense  with  com- 


582  ALLOY  STEELS 


pensation.  It  is  known  as  invar.  Finally,  46%  nickel  steel,  containing 
only  .15%  carbon,  is  known  as  platinite,  because  it  has  about  the  same 
coefficient  of  expansion  as  platinum  and  glass.  Hence,  it  is  employed  in 
the  lead  wires  of  incandescent  lamp  bulbs,  where  formally  platinum  was 
held  to  be  indispensable.  Later,  a  38%  nickel  steel  wire,  Coated  with 
copper,  was  found  to  give  better  satisfaction  than  platinite. 

Reasons  for  These  Peculiarities  of  the  Nickel  Steels:  A  study  of 
the  explanation  offered  to  account  for  the  peculiar  influence  of  nickel  upon 
steel  is  both  interesting  and  instructive.  Referring  again  to  the  3.5%  nickel 
steel,  it  is  to  be  noted  that  nickel  primarily  influences  the  strength  of  the 
steel,  and,  to  a  less  degree,  the  ductility.  These  facts  are  explained  when 
the  solubility  of  nickel  in  iron  is  considered.  Thus,  when  nickel  is  added 
to  steel,  say  of  hypo-eutectoid  composition,  it  dissolves  in  the  iron  to  form 
an  iron-nickel  alloy.  When  this  steel  is  cooled  through  the  critical  range, 
it  is  this  alloy  that  replaces  both  the  free  ferrite  and  the  pearlitic  ferrite 
of  the  carbon  steel.  Naturally,  a  change  in  the  physical  properties  due  to 
this  fact  alone  are  to  be  expected.  But  it  is  in  the  influence  of  this  alloy 
upon  the  formation  of  pearlite  that  the  reason  for  the  great  increase  in 
tensile  strength  of  nickel  steel  is  found.  The  separation  of  the  cementite 
from  the  iron-nickel-carbon  solution  does  not  take  place  as  readily  as  from 
a  plain  iron-carbon  solution,  hence  the  pearlite  areas  are  larger  and  less 
clearly  defined  than  in  plain  carbon  steels.  In  other  words,  just  as  carbon 
and  rapid  cooling  are  obstructing  agents  to  the  transformation  from 
austenite  to  pearlite,  so  also  does  the  nickel  act  in  a  similar  manner.  As 
long  as  the  nickel  content  is  very  low,  not  over  2%,  this  influence  shows 
itself  only  in  a  slight  change  in  the  physical  properties  as  noted.  These 
changes  become  more  marked  with  increase  of  nickel,  as  is  to  be  expected, 
but  the  quick  change  in  heat  treating  properties  at  8%  or  10%  and  at  about 
25%  are  not  thus  accounted  for.  A  little  reflection,  however,  shows  all 
these  characteristics  to  be  due  to  the  same  cause,  namely,  the  retarding 
action  of  the  nickel  upon  the  transformation  ranges.  One  writer  represents 
this  influence  of  nickel  upon  the  critical  points  in  heating  as  follows: 

.01%  Nickel  lowers  the  Ac3  range  .235°  C. 

.01%       "  "         "    Ac  3-2  range  .180°  C. 

.01%       "  "         "    Ac  2  range  .087°  C. 

.01%       "  "         "    Ac  ±  range  .103°  C. 

No  figures  are  given  for  the  Ar  points,  but  other  authorities  have 
established  that  the  Ar^  point  is  about  80°  C.  below  the  Aci  point.  In 
addition  to  and  in  connection  with  these  facts,  the  effect  of  nickel  upon 
the  eutectoid  ratio  should  also  be  considered.  The  statement  that  nickel 
interferes  with  the  free  formation  of  pearlite  has  already  been  made,  and 
it  now  remains  to  be  pointed  out  that  nickel,  up  to  about  8%,  reduces  the 
eutectoid  ratio  below  that  for  straight  carbon  steels.  According  to 
Bullens  the  eutectoid  for  a  steel  containing  3%  nickel  is  reached  when 
the  carbon  content  is  .75%  and  for  one  containing  7%  nickel  this  value 


NICKEL  STEELS 


583 


falls  to  .60%  carbon.  All  these  facts,  as  they  relate  to  the  3%  nickel  steel, 
which  is  the  one  we  are  most  interested  in,  have  been  assembled  and  are 
represented  in  the  accompanying  diagram  copied  after  Bullens,  who  was 
the  first  to  represent  the  effects  of  nickel  in  this  way. 


9.-0 


.9 


Fia.  119.     Diagram  Showing  effect  of  Nickel  Upon  the  Critical  Ranges. 
Compared  with  Carbon  Steel.    (After  Bullens,  Steel  and  its  Heat  Treatment. 


584  ALLOY  STEELS 


The  preceding  diagram  is  intended  to  depict  the  general  effects  of  nickel 
upon  the  transformation  ranges,  which  become  lower  and  lower  as  the 
nickel  content  is  increased,  and  the  eutectoid  ratio  which  decreases  with 
increase  of  nickel.  The  diagram  shows  the  position  of  the  Ac  and  Ar  points 
for  carbon  steel  and  also  for  steel  containing  3%  nickel.  Thus: 

Solid  line  indicates  the  position  of  the  ranges  on  cooling  carbon  steel. 
Dotted  line  indicates  the  position  of  the  ranges  on  heating  carbon  steel. 
Dot  and  dash  line  indicates  the  position  of  the  ranges  on  heating  3%  nickel 

steel. 
Dash  and  dash  line  indicates  approximately  the  position  of  the  ranges  on 

cooling  3%  nickel  steel.     Due  to  a  number  of  factors,    the  Arranges 

are  subject  to  considerable  variation. 

When  the  nickel  content  has  been  increased  to  25%,  these  ranges  are 
found  to  lie  in  a  position  that  is  entirely  below  atmospheric  temperatures. 

Structural  Changes  Due  to  Nickel :  From  the  preceding  data  a  simple 
calculation  will  show  that  as  the  nickel,  or  nickel  and  carbon  contents,  are 
increased,  the  transformation  ranges  are  progressively  lowered  until  they 
reach  atmospheric  temperatures.  This  fact  forms  a  basis  for  the  classi- 
fication of  the  nickel  steels,  which  are  divided  into  the  following  three 
divisions: 

1.  Pearlitic-Nickel  Steels  are  those  in  which  the  nickel  and  carbon 
contents  are  such  that,  when  slowly  cooled  from  a  high  temperature,  they 
will  consist  in  whole  or  in  pare  of  pearlite.     In  these  steels  the  nickel  ranges 
from  0  to  10%  and  follows  inversely  the  percentage  of  carbon,  which  theo- 
retically ranges  from  0.  to  1.60%. 

2.  Martensitic-Nickel  Steels:     In  these  steels  the  nickel  and  carbon 
contents  are  high  enough  to  lower  the  critical  ranges  to  such  a  degree  that 
only  a  partial  transformation  from  austenite  to  pearlite  occurs  even  on 
slow  cooling.     In  these  steels  the  nickel  contents  range  from  10%  to  25% 
with  the  carbon  varying  as  above. 

3.  Austenitic=Nickel  Steels:    Above  25%  the  influence  of  the  nickel 
is  so  great  that  the  transformation  range  is  lowered  to  atmospheric  tem- 
peratures, and  the  steel  is  always  austenitic  regardless  of  the  carbon  content. 
As  previously  pointed  out,  only  the  pearlitic  steels  containing  about  3.50% 
nickel  are  of  real  importance  commercially. 

The  Constitutional  Theory  of  Ternary  Steels:  In  causing  these 
structural  changes  the  action  of  nickel  is  in  accord  with  that  of  all  the 
alloying  elements.  Briefly  stated,  the  theory  is  that,  upon  the  introduction 
of  a  third  element  into  a  given  carbon  steel,  the  steel  remains  at  first 
pearlitic  in  structure,  but  as  the  content  of  the  special  element  is  increased 
the  steel  becomes  martensitic,  then  austenitic  or  cementitic,  depending 
upon  the  chemical  action  and  alloying  powers  of  the  special  element  with 


NICKEL  STEEL 


585 


respect  to  carbon  and  iron;  and  also  that  by  keeping  the  amount  of  the 
special  element  constant,  the  same  transformations  may  be  effected  by 
raising  the  carbon  content.  This  statement,  in  so  far  as  it  relates  to  nickel, 
steels  is  expressed  diagrammatically  in  the  accompanying  figure. 


FIG.  120. 


Per  Cent.  Carbon 
Constitutional  Diagram  for  the  Nickel  Steels. 


This  diagram -shows  that  with  a  very  low  carbon  content,  say  about 
.05%,  the  steel  remains  in  the  pearlitic  condition  until  the  nickel  content 
reaches  10%,  when  it  will  be  found  to  be  in  the  martensitic  condition.  With 
a  nickel  content  of  30%  the  same  steel  would  be  austenitic.  But  with  a 
carbon  content  of  about  .80%,  for  example,  the  steel  becomes  martensitic 
when  the  nickel  content  exceeds  6%,  and  austenitic  when  it  reaches  16% 
or  17%.  Diagrams  like  the  preceding  are  useful  in  illustrating  the  effect 
of  the  different  alloying  elements  and  will  frequently  be  made  use  of  in 
the  discussions  to  follow. 

Heat  Treating  Pearlitic  Nickel  Steels:  From  what  has  been  said,  it 
should  be  apparent  that  the  heat  treating  of  nickel  steel,  to  secure  the 
desired  results,  is  an  art  that  requires  much  experience  and  knowledge. 
Hence,  it  is  only  desirable  to  indicate  what  should  be  the  proper  treatment 
for  this  steel,  and  although  the  heating  and  cooling  of  this  steel  presents 
some  phenomena  quite  distinctive  from  carbon  steels,  it  is  considered  that 
this  object  has  already  been  attained.  However,  a  few  remarks  as  to  how 
the  low  nickel  steels  are  benefited  by  heat  treatment  may  not  be  out  of 


586 


ALLOY  STEELS 


place.  A  heat  treated  nickel  steel  has  a  lower  reduction  and  elongation 
than  a  correspondingly  heat  treated  steel  without  nickel,  but  the  increase 
in  strength  is  much  greater.  Thus,  for  the  same  strength,  the  nickel  steel 
is  much  tougher,  and  on  this  account  nickel  is  much  to  be  preferred  to  carbon 
for  increasing  tensile  strength.  The  tensile  strength  and  elastic  limit  are 
both  affected  by  the  temperature  of  the  drawback,  being  decreased  as  this 
temperature  is  raised,  but  the  reduction  in  area  and  elongation  are  not 
so  correspondingly  and  gradually  increased  as  in  the  plain  steels.  In  this 
connection,  a  study  of  tables  62  and  65  will  be  found  of  value. 


Table  65:     Illustrating  the   Effect  of  Various  Heat  Treatments  upon 
the  Mechanical  Properties  of  Three  Per  Cent  Nickel  Steels. 

Chemical  Composition:  C.  .37%,  Mn.  .61%,  Si.  .22%,  P.  .022%, 
S.  .034%,  Ni.  3.27%. 

Description  of  Pieces  Treated:  One  inch  rounds,  25  inches  long; 
14  pieces,  all  from  same  billet. 

Description  of  Test  Pieces:  One  test  piece  from  each  of  the  14 
pieces,  turned  to  a  diameter  of  ^  inch,  as  in  Fig.  47. 


HEAT  TREATMENT 

PHYSICAL  TEST 

Anneal   and 
Hardening  and          Draw 
Refining,  Deg.  C       Deg.  £ 

Tensile 
Strength 

Elastic 
Limit 

Elongation 

in  2  '  % 

Reduction 
m  area    % 

Brinell 
Number 

Scleros- 
cope  Test 

As  Rolled 

113,000 

69,000 

22.5 

47.7 

229 

32 

Heated  to  76 

0°  and 

cooled  in  F 

urnace 

99,000 

60,000 

26.1 

48.3 

183 

26 

Heated  to 

427° 

168,000 

150,000 

13.5 

47.2 

331 

48 

815°  quench- 
ed in  oil 

482° 
538° 

148,000 
133,000 

131,000 
118,000 

18.0 
21.0 

48.3 
57.3 

285 
262 

44 
40 

593° 

110,000 

90,000 

28.0 

64.7 

217 

33 

649° 

104,000 

70,000 

28.0 

63.0 

207 

27 

704° 

95,000 

62,500 

28.5 

51.7 

179 

26 

Heated  to 

427° 

185,000 

165,000 

13.0 

51.1 

352 

50 

815°  quench- 

482° 

150,000 

136,000 

17.5 

47.2 

311 

44 

ed  in  water 

538° 

148,000 

135,000 

16.0 

54.7 

293 

44 

593° 

133,500 

115,000 

18.5 

56.5 

269 

37 

649° 

108,000 

80,000 

27.5 

62.8 

223 

32 

704° 

98,000 

67,000 

28.0 

58.6 

179 

29 

CHROME  STEEL  587 


SECTION   III. 

CHROME    STEEL. 

The  Manufacture  of  Simple  Chromium  Steels  is  carried  on  by  the 
open  hearth,  the  electric,  or  the  crucible  process.  At  the  temperature 
of  molten  steel,  chromium  is  capable  of  reducing  iron  oxides,  hence  it  is 
oxidized  to  a  great  extent  in  the  open  hearth,  especially  during  the  melting 
and  boiling  of  the  charge.  All  simple  chrome  steel  is  made  by  the  addition 
of  ferro-chromium  to  the  charge.  When  the  steel  is  made  in  crucibles,  the 
ferro-chromium  is  added  with  the  original  charge;  if  in  the  electric  furnace, 
this  addition  may  be  made  at  any  time;  but  if  made  in  the  open  hearth 
furnace,  the  ferro-chromium  is  added  to  the  steel  just  long  enough  before 
casting  for  the  alloy  to  be  melted  and  become  well  mixed  through  the 
charge,  as  otherwise  great  waste  of  the  chromium  results.  Chromium, 
however,  is  not  oxidized  readily  enough  to  be  of  any  value  as  a  curative 
or  a  deoxidizing  agent,  and  is  used  only  for  its  effect  as  an  alloying  element. 
Simple  chromium  steels  are  worked  by  the  same  methods  and  in  the  same 
way  as  carbon  steels,  but  unlike  nickel  steels,  they  are  seldom,  if  ever,  used 
in  their  natural  state,  heat  treatment  being  necessary  to  develop  the  bene- 
ficial effects  of  the  chromium,  which  is  most  active  in  responding  to  this 
treatment.  Simple  chromium  steel  was  one  of  the  first  alloy  steels  to  be 
made. 

Influence  of  Chromium:  This  element  is  preeminently  a  hardening 
agent  in  steel.  Unlike  nickel,  which  merely  dissolves  in  iron,  chromium 
forms  a  carbide.  In  steel,  therefore,  at  least  a  part  of  the  chromium  will 
be  in  this  form;  but  it  never  reacts  with  the  carbon  to  the  exclusion  of  iron, 
arid  in  steel  this  carbide  may  exist  either  as  iron-chromium  carbide, 
xFe3C-yCr3C2  or  as  a  solution  of  FesC  and  Cr3C2.  Thus,  while  nickel 
is  found  in  the  ferrite  of  the  steel,  chromium  is  associated  with  the  cementite, 
and  imparts  what  might  be  termed  a  mineral  hardness  to  the  steel.  But 
the  great  hardness  of  the  chrome  steels  is  due,  also,  to  another  cause. 
This  iron-chromium  cementite  is  not  as  readily  dissolved  or  diffused  as 
the  ordinary  cementite  on  heating  the  steel  through  the  critical  range, 
nor  does  it  segregate,  or  separate  to  form  pearlite,  as  readily  on  cooling. 
This  fact  accounts,*for  the  peculiar  changes  in  the  critical  ranges  of  the 
steel  that  the  addition  of  small  amounts  of  this  element  brings  about,  for 
while  it  tends  to  raise  the  Ac  range  it  also  lowers  the  Ar  range.  Thus, 
in  quenching  it  helps  to  prevent  the  transformation  of  the  austenite,  and 
so  adds  much  to  the  hardness  in  this  way.  From  these  statements  it  is 
to  be  inferred  that  chromium  may  have  no  hardening  power  when  not  in 
the  presence  of  carbon.  Such  a  conclusion  agrees  with  the  facts,  as  it  has 
been  shown  by  Harbord  that  very  low  carbon  chrome  steels  have  prac- 
tically no  hardening  power.  It  is  now,  also,  easily  understood  why  the 
degree  of  hardness"  of  the  steel  is  dependent,  within  certain  limits,  upon 


588 


ALLOY  STEELS 


the  carbon  content  as  well  as  upon  the  chromium.  An  exceedingly  fine 
grain  structure  is  characteristic  of  heat  treated  chrome  steels,  which  fine- 
ness of  grain  confers  the  valuable  property  of  toughness.  Thus,  the  net 
result  from  the  influence  of  this  element  is  to  increase  the  tensile  strength 
and  elastic  limit,  without  a  noticeable  loss  in  the  ductility.  One 
investigator  has  found  chromium  to  be  very  efficient  in  retarding  corrosion 
of  the  steel  by  neutral  media,  such  as  sea  water,  and,  therefore,  recommends 
its  use  in  ship  plates. 

The  Microscopic  Constituents  of  the  Chrome  Steels :  The  influence 
of  chromium  and  carbon  in  determining  the  constitution  of  the  steel  is 
shown  in  the  accompanying  diagram. 


Cementitic  Structure 

(Double,  Iron,  Chromium  Carbide 

in  Matrix  of  Martensite) 


1.20 


1.40 


1.00 


Per.  Cent.  Carbon 
FIG.     121.     Constitutional  Diagram  for  Chromium  Steels. 


From  this  diagram  it  is  seen  that,  when  the  chromium  content  exceeds 
7%  in  steels  of  low  carbon  content  or  about  5%  in  steels  of  high  carbon 
content,  the  steel  is  composed  only  of  martensite,  hence  is  very  hard  and 
strong,  but  is  lacking  in  ductility  and  is  inclined  to  be  brittle.  It  can  be 
neither  hardened  nor  softened  by  heat  treatment.  It  will  be  noted  that 
unlike  nickel,  increasing  the  chromium  content  beyond  a  certain  limit  in 
a  steel  with  a  given  carbon  content  fails  to  produce  the  austenitic  condition, 
but  gives  a  new  structure  made  up  of  grains  of  the  double  carbide  embedded 
in  martensite.  Between  these  two  areas  is  a  narrow  range  in  which  the 
carbide  grains  are  somewhat  less  numerous  than  in  the  cementite  region 
proper.  This  range  marks  the  gradual  transition  from  the  martensitic  to 
the  cementitic  condition  with  the  gradual  increase  in  the  chromium  and 
the  carbon  content.  Like  the  martensitic  condition,  steel  of  cementitic 
composition  is  not  affected  by  heat  treatment.  For  obvious  reasons,  then, 
to  produce  steels  of  greatest  usefulness,  the  chromium  content  will  be 
restricted  to  that  required  to  give  the  pearlitic  condition  only. 


CHROME  STEELS  589 


Uses  of  the  Simple  Chrome  Steels:  These  steels  are  used 
wherever  extreme  hardness  is  desired.  Thus,  they  have  long  been  used 
for  stamp  shoes  and  dies  for  crushing  hard  ores,  like  some  of  the  gold  and 
silver  ores.  Another  use  is  for  five-ply  plates  for  safes,  where  their  great 
hardness  is  valued  on  account  of  the  resistance  they  offer  to  the  drilling 
tools  used  by  burglars.  Rolls  for  cold  rolling  metals  are  made  of  steel 
containing  about  .9%  carbon  and  2%  chromium,  while  several  thousand 
tons  of  steel  containing  about  1.30%  carbon  and  .5%  chromium  are  used 
annually  for  files.  It  is  often  used  in  steel  for  various  special  purposes, 
as  for  example  the  steel  known  by  the  name  of  "Crucia,"  which  is  nothing 
more  than  a  good  grade  of  spring  steel  to  which  has  been  added  from  .20% 
to  .40%  chromium.  The  Carnegie  Steel  Company  manufactures  this  steel 
as  a  part  of  their  regular  product.  A  type  for  axes  and  hammers,  which 
contains  .60%  to  .70%  carbon  and  .60%  to  .90%  chromium;  another  for 
chains,  containing  .25%  to  .33%  carbon  and  .65%  to  .95%  chromium;  and 
a  third  for  track  bolts  with  .25%  to  .40%  carbon  and  .60%  to  .90%  chromium 
are  also  manufactured  by  this  company.  But  the  most  important  use  for 
these  steels  is  in  the  balls  and  rolls  for  bearings.  For  this  purpose  they  are 
employed  in  low  carbons  for  case  hardening  and  in  high  carbons  for  heat 
treating,  i.  e.,  quenching  and  tempering.  Of  the  tonnage  furnished  by 
Carnegie  Steel  Company  for  this  purpose,  that  for  case  hardening  is  made 
in  the  open  hearth,  while  the  high  carbon  material  is  produced  in  the  electric 
furnace. 

Heat  Treatment  of  Simple  Chrome  Steel:  To  cite  an  example  of  the 
high  grade  of  chrome  steel:  One  large  maker  of  bearings  uses  steel  con- 
taining carbon,  1.10%;  chromium,  1.40%;  manganese,  0.35%;  sulphur, 
0.025%;  and  phosphorus,  0.025%.  Sizes  smaller  than  one-half  inch  diam- 
eter are  heat-treated  by  being  quenched  in  water  from  774°  C.  and  then 
drawn  to  190°  C.  for  half  an  hour.  For  larger  balls,  the  quenching  tem- 
perature is  802°  C.  The  second  heating  does  not  produce  even  an  oxide 
color,  but  is  enough  to  relieve  in  some  degree  the  internal  stresses  due 
to  the  irregular  cooling  of  quenching,  so  that  the  balls  are  less  liable  to 
crack  spontaneously  or  to  be  broken  in  use.  The  strength  of  a  good,  well- 
treated  ball  is  prodigious;  a  ball  three-fourths  of  an  inch  in  diameter,  tested 
by  the  three-ball  method,  sustained  a  load  of  52,000  pounds.  On  the  small 
area  of  contact  the  intensity  of  the  pressure  amounts  to  over  one  million 
pounds  per  square  inch.  The  Society  of  Automobile  Engineers  recommends 
less  chromium  than  that  given  above,  or  1  to  1.2  per  cent.  The  critical 
ranges  for  these  steels  containing  .90%  carbon,  vary  about  as  follows: 

For  a  chromium  content  of    .50%,  from  720°  C.  to  745°  C. 
For  a  chromium  content  of  1.50%,  from  760°  C.  to  785°  C. 

As  indicating  what  may  be  expected  by  varying  the  treatment  of  the 
steels  of  this  grade,  the  following  will  serve  as  an  illustration: 


590 


ALLOY  STEELS 


Table  66.     Physical  Properties  of  a  Heat  Treated  Chrome  Steel. 

Material:     1  inch  rounds. 

Analysis:    C.,  .64%;  Mn.,  .27%;  Si.,  .18%;  Cr.,  1.01%. 

Treatment:     Heated  to  870-871°  C.     Quenched  in  oil,   and  tempered  as 
indicated. 


TEMPERING 
TEMPER- 
ATURES 

TENSILE 

STRENGTH 

ELASTIC 
LIMIT 

ELONGA- 
TION IN 
2  INCHES 

REDUCTION 
IN  AREA 

BRINNEL 
HARD- 
NESS 

400°  C. 
500°  C. 
600°  C. 

228,000 
212,500 
186,500 

170,500 
155,500 
128,000 

5.2% 
8.4% 
10.3% 

13.7% 
19.8% 

22.2% 

478 
445 
389 

SECTION    IV. 

CHROME — NICKEL   STEELS. 

Influence  of  Chromium  and  Nickel  When  Combined:  Having 
considered  the  effects  of  chromium  and  nickel  when  added  separately  to 
the  steel,  the  student  is  interested  in  knowing  what  their  combined  influence 
may  be.  In  the  woids  of  Bullens,  an  impartial  judge  of  high  standing  as 
an  authority  upon  the  subject  of  alloy  steels,  especially  from  a  practical 
standpoint:  "The  chrome-nickel  steels  probably  represent  the  best  all- 
round  alloy  steels  in  commercial  use  for  general  purposes.  Chrome-nickel 
steels  of  suitable  composition  appear  to  have  combined  in  them  the  beneficial 
effects  of  both  the  chrome  and  nickel,  but  without  the  disadvantages  which 
are  inherent  in  the  use  of  either  one  separately.  Moreover,  the  presence  of 
both  chrome  and  nickel  seems  to  intensify  certain  physical  characteristics. 
To  the  increased  ductility  and  toughness  conferred  by  nickel  on  the  ferrite 
there  is  added  the  mineral  hardness  given  to  the  cementite  and  pearlite 
by  the  chrome,  but  with  a  greater  resultant  effect.  Again,  while  the 
addition  of  nickel  alone  serves  to  diminish  the  susceptibility  to  brittleness 
in  the  steel  upon  prolonged  heating  or  sudden  cooling — in  comparison  with 
the  corresponding  straight  carbon  steels — and,  on  the  other  hand,  the 
presence  of  chrome  alone  tends  to  the  opposite  effect,  a  suitable  combination 
of  the  two  alloying  elements  tends  to  neutralize  the  harmful  effects  and 
also  to  magnify  the  good  points.  This  is  not  only  brought  out  in  the  static 
strength  and  ductility,  but  also  in  the  dynamic  strength  or  fatigue 
resistance." 

Types  of  Chrome=Nickel  Steel :  According  to  the  testimony  of  some 
heat  treating  experts  there  appears  to  be  a  certain  ratio  of  chrome  to  nickel 
which  gives  the  most  efficient  combination  of  the  physical  properties. 
Thus,  if  the  nickel  and  chromium  are  present  in  the  right  proportions,  the 
lesser  susceptibility  of  the  nickel  to  brittleness,  for  example,  will  so  modify 
the  greater  tendency  to  brittleness  which  is  given  by  chrome  alone,  that 
a  better  steel  is  obtained  than  when  this  ratio  is  not  observed.  This  ratio 
is  said  to  be  about  2^  parts  of  nickel  to  one  part  of  chromium.  Further- 
more, it  is  claimed  that  if  the  chromium  content  greatly  exceeds  this  relation 


CHROME-NICKEL  STEEL 


591 


to  nickel,  the  temperature  limits  are  so  narrowed  that  the  successful  treat- 
ment of  the  steel  is  made  very  difficult.  .Thus,  in  the  three  standard  types 
of  these  steels,  known  as  low  nickel-chrome  steel  containing  about  1.5% 
nickel,  medium  nickel-chrome  steel  with  about  2.50%  nickel,  and  high 
nickel-chrome  steel,  in  which  the  nickel  content  rises  to  that  of  the  simple 
nickel  steels  with  3.5%  nickel,  the  chromium  content*  should  be  approxi- 
mately .60%,  1.00%  and  1.50%,  respectively. 

Mayari  Steel,  termed  a  natural  chrome-nickel  steel,  is  made  from 
certain  ores  found  at  Mayari,  Cuba.  These  ores  contain  enough  nickel 
and  chromium  to  give  a  pig  iron  with  1.3%  to  1.5%  nickel  and  2.5%  to  3.0% 
chromium.  When  this  iron  is  converted  into  steel,  for  which  purpose  the 
open  hearth  or  the  duplex,  Bessemer-open  hearth,  processes  are  employed, 
practically  all  the  nickel  remains  in  the  steel,  but  a  large  part  of  the  chrom- 
ium is  wasted.  The  steel  is  thus  a  species  of  low-nickel-chrome,  containing 
roughly  from  1.00%  to  1.50%  nickel  and  from  .20%  to  .70%  chromium. 
This  steel  is  undoubtedly  of  excellent  quality  for  certain  purposes,  but 
where  the  highest  quality  of  chrome-nickel  steel  is  required,  most  authori- 
ties agree  that  the  synthetic  alloy  steels  are  superior. 

Uses  of  Chrome=Nickel  Steels:  Low  chrome  nickel  steel  is  the  type 
more  commonly  employed  because  of  its  low  price  and  the  greater  ease  by 
which  it  is  machined.  In  static  properties  it  is  nearly  equal  to  the  higher 
nickel  grades,  but  in  resistance  to  dynamic  stresses,  shocks,  etc.,  the  latter 
are  superior.  Besides,  since  the  purpose  to  which  it  is  adapted  is 
about  the  same  as  3.5%  simple  nickel  steel,  low-nickel  chrome  is  being 
substituted  for  this  steel,  also  on  account  of  the  price.  All  three  grades 
are  used  in  automobiles,  the  carbon  content  being  varied  about  as  shown 
in  the  following  table: 


TABLE  67:      Grades  and  Composition  of  Nickel-Chrome  Steels. 


GRADE 

CARBON 

% 

MN. 
MAX.  % 

Si. 
% 

S. 
MAX.  % 

P. 
MAX.  % 

Ni. 

% 

CR. 

% 

Low  

0.20  to  0.55 

0.70 

Low 

0.050 

0.04 

1.25 

0.60 

Medium.  . 

.20  to    .55 

.70 

Low 

.050 

.04 

1.75 

1.10 

High.... 

.20  to    .55 

.70 

Low 

.050 

.04 

3.50 

1.50 

An  important  use  of  these  steels  is  in  armor  plate.  Thick  armor  is 
face  hardened  by  a  carbonizing  process,  but  the  body  has  the  original 
composition,  which  is  approximately  as  follows:  C.,  .33%;  Mn.,  .32%; 
S.,  .03%;  P.,  .014%;  Si.,  .06%;  Ni.,  4.00%;  and  Cr.,  2.00%.  Medium  armor, 
three  to  five  inches  in  thickness,  is  not  face  hardened,  but  is  given  high 
properties  throughout  by  the  proper  heat  treatment.  The  composition  of 


592  ALLOY  STEELS 


this  armor  is  approximately,  C.,  .30%;  Mn.,  .34%;  S.,  .03%;  P.,  .03%; 
S  .,  .13%:  Ni.,  3.66%,  and  Cr.,  1.45%.  The  nickel  chromium  steels  are 
used  in  the  manufacture  of  most  armor  piercing  projectiles,  also. 

Heat  Treatment  of  Chrome=Nickle  Steels:  The  heat  treatment  of 
these  steels  is  about  the  same  in  kind  and  method  as  that  for  simple  nickel 
and  chrome  steels,  and  is  varied  to  suit  the  kind  of  material  and  the  purpose 
for  which  the  steel  is  to  be  used.  To  give  a  general  idea  of  the  proper 
treatment  for  these  steels,  the  recommendations  of  Bullens  may  be  cited: 

I.  "For  forgings: 

a.  Quench  in  oil  from  about  175°  to  200°  F.  (97°  to  110°C.)  over 
the  critical  range. 

b.  Quench  in  oil  from  about  50°F  (28°C)  over  the  critical  range. 

c.  Anneal    at    about   75°F    (42°C)    under  the  critical  range  and 
machine. 

d.  Quench  in  the  proper  medium  from  about  50  °F  (28  °C)  over  the 
range. 

e.  Draw  the  temper  to  suit  the  work  in  hand." 

II.  "For  shafts  and  other  structural  parts  in  which  the  desired  physical 

properties  may  be  obtained  by  a  drawing  temperature  of  about 
900 °F  (500°  C.)  or  over,  and  which  will  leave  the  steel  in  a 
machinable  condition,  treatment  I.  may  be  modified  at  (c)  as  thus 
noted,  and  no  further  treatment  will  be  required. 

a.  Quench  in  oil  from  about  175°  to  200°  F  (97°  to  110°C)  over 
the  critical  range. 

b.  Quench  in  oil  from  about  50°F  (28°C)  over  the  critical  range. 

c.  Draw  at  900°F  (482°C)    or  more,  as  the  work  may  require. 
Machine." 

III.  "The  full  treatment  as  given  under  (I)  may  be  modified,  if  desired 

to  the  following,  for  parts  to  be  drawn  below  900°  or  1000°  F. 
(482°  or  540  °C.) 

a.  Quench  in  oil  from  about  175°  to  200°  (97  to  110°C)  over  the 
critical  range. 

b.  Reheat  to  about  25°  to  50°  F.  (14°  to  28°C)  over  the  critical 

range  and  cool  slowly.     Machine. 

c.  Quench  in  oil  from  about  50°  (28°C)  over  the  critical  range. 

d.  Draw  to  the  temperature  required  by  the  work." 


ALLOY  STEELS 


593 


The  data  supplied  in  tables  68  and  69  will  serve  as  a  basis  for  comparing 
the  mechanical  properties  of  the  chrome-nickel  steels,  both  in  their  natural 
and  heat-treated  states 


Table  68 :     Illustrating  the  Effect  of  Various  Heat  Treatments  upon  the 
Mechanical  Properties  of  Low=Chrome=Nickel  Steels. 

Chemical  Composition:  C.  .39%,  Mn.  .52%,  Si.  .18%,  P.  .017%, 
S.  .042%,  Ni.  1.18%,  Cr.  .58%. 

Description  of  Pieces  Treated;  One  inch  rounds,  25  inches  long; 
14  pieces,  all  from  same  billet. 

Description  of  Test  Pieces;  One  test  piece  from  each  of  the  14 
pieces,  turned  to  a  diameter  of  %  inch,  as  in  Fig.  47. 


HEAT  TREATMENT 


PHYSICAL  TESTS 


Hardening  and 
Refining  Deg.  C 

Anneal  and 
Draw, 
Deg.  C 

Tensile 
Strength 

Elastic 
Limit 

Elongation 
in  2"% 

Reduction 
in  area% 

Brinell 
Number 

Scleros- 
copeTest 

As  Rolled 

99,000 

59,000 

25.5 

54.4 

208 

29 

Heated  to 

760°  and 

89,000 

54,000 

30.0 

56.5 

170 

25 

cooled  in  F 

urnace 

Heated  to 

427° 

139,000 

114,000 

15.5 

51.4 

331 

42 

845°  quench- 
ed in  oil 

482° 
538° 

130,000 
113,000 

113,000 
88,000 

15.0 
17.5 

53.9 
59.8 

321 
255 

44 
34 

593° 

113,000 

86,000 

21.0 

62.8 

229 

32 

649° 

108,000 

81,000 

25.0 

64.7 

229 

31 

704° 

97,000 

70,000 

27.0 

67.7 

207 

29 

Heated  to 

427° 

174,000 

158,000 

14.0 

47.2 

363 

46 

845°  quench- 

482° 

150,000 

135,000 

16.5 

45.7 

221 

44 

ed  in  water 

538° 

140,000 

125,000 

20.0 

55.2 

285 

44 

593° 

124,000 

108,000 

22.0 

60.8 

255 

40 

649° 

110,000 

91,000 

26.0 

66.0 

229 

33 

704° 

90,000 

70,000 

34.0 

69.2 

187 

25 

594 


ALLOY  STEELS 


Table  69 :     Illustrating  the  Effect  of  Various  Heat  Treatments  upon  the 
Mechanical  Properties  of  High=Chrome=Nickel  Steel. 

Chemical  Composition;  C.  .34%,  Mn.  .64%,  Si.  .20%,  P.  .010%, 
S.  .036%,  Ni.  3.65%,  Cr.  1.24%. 

Description  of  Pieces  Treated;  One  inch  rounds,  25  inches  long; 
14  pieces,  all  from  same  billet. 

Description  of  Test  Pieces;  One  test  piece  from  each  of  the*  14 
pieces,  turned  to  a  diameter  of  %  inch,  as  in  Fig.  47. 


HEAT  TREATMENT 


PHYSICAL  TESTS 


Hardening  and 
Refining  Deg.  C 

Anneal  and 
Draw, 
Deg.  C. 

Tensile 
Strength 

Elastic 
Limit 

Elongation 
in  2"% 

Reduction 
in  area  % 

Brinell 
Number 

Scleros- 
cope  Test 

As  Rolled 

172,500 

138,000 

11.5 

26.5 

444 

57 

Heated  to  76 

0°  and 

125,000 

78,000 

18.0 

47.2 

255 

38 

cooled  in  F 

urnace 

Heated  to 

427° 

190,000 

166,000 

12.5 

50.0 

415 

55 

845°  quench- 
ed in  oil 

482° 
538° 

170,000 
142,000 

154,000 
126,000 

15.0 
20.0 

44.3 

57.8 

341 
321 

41 
43 

593° 

127,500 

115,000 

22.0 

62.3 

285 

36 

649° 

117,000 

99,000 

23.0 

64.7 

255 

37 

704° 

115.000 

69,000 

24.0 

56.0 

255 

35 

Heated  to 

427° 

164,000 

152,000 

17.5 

56.0 

375 

51 

845°  quench- 

482° 

160,000 

147,500 

15.5 

53.9 

341 

48 

ed  in  water 

538° 

145,000 

130,000 

21.0 

58.6 

321 

43 

593° 

124,000 

100,000 

22.5 

62.8 

269 

40 

649° 

120,000 

99,000 

24.0 

63.7 

248 

36 

704° 

120,000 

69,000 

17.0 

50.0 

269 

36 

VANADIUM  STEEL 


595 


SECTION    V. 

VANADIUM    STEELS. 

Simple  Vanadium  Steels  do  not  at  present  have  the  standing  they 
formerly  had,  and  the  only  reason  for  mentioning  them  here  is  to  enable 
the  reader  to  get  an  idea  of  the  effects  of  vanadium  alone,  so  that  he  can 
better  understand  the  reasons  for  chrome  vanadium  steel,  to  be  considered 
later.  Since  1917  the  Carnegie  Steel  Company  has  manufactured  but 
one  grade  of  vanadium  steel,  known  as  type  "F,"  which  is  used  as  a  flux 
in  oxyacetylene,  oxyhydrogen,  and  electric  welding. 

Influence  of  Vanadium:  Unlike  nickel  and  chromium,  vanadium  is 
an  intense  deoxidizing  agent,  being  capable  of  carrying  the  cleansing  of  the 
steel  beyond  the  point  obtainable  by  manganese,  or  even  silicon  and 
aluminum.  Thus,  this  element  performs  the  double  function  of  a  curative 
and  an  alloying  element.  It  is  added  to  the  steel,  in  the  form  of  ferro- 
vanadium,  containing  about  35%  of  the  element,  at  the  time  of  tapping,  if 
the  steel  is  being  made  by  the  open  hearth  process,  and  preferably  after 
the  other  ladle  additions  to  avoid  undue  wastage.  Of  the  vanadium  that 
is  retained  by  the  steel,  only  very  small  amounts,  from  .15%  to  .25%,  are 
required  to  affect  the  physical  properties  of  the  steel.  Like  most  of  the 
alloying  elements,  it  tends  to  give  a  finer  and  denser  structure  than  that 
of  carbon  steel,  and  for  the  most  part  its  action  is  similar  to  other  alloying 
elements.  But  in  some  respects,  at  least,  it  presents  characteristic 
phenomena.  Thus,  there  are  good  reasons  to  believe  that,  when  present 
even  in  the  small  amounts  noted  above,  it  is  both  dissolved  in  the  ferrite, 
like  nickel,  and  exists  as  a  carbide  or  a  double  carbide  in  the  cementite, 
like  chromium.  It  has  a  powerful  influence  upon  the  transformation  ranges, 
as  is  seen  from  the  fact  that  while  steels  containing  .2%  carbon  and  .7% 
vanadium,  or  .8%  carbon  and  .5%  vanadium,  are  pearlitic,  any  increase 
of  the  vanadium  content  over  these  limits  renders  the  steel  cementitic  as 
shown  in  the  following  diagram: 


Cement  itt 


1.00         1.20 


1.40 


1.60 


Per  Cent.  Carbon 
FIG.  122.     Constitutional  Diagram  for  Vanadium  Steels. 

As  revealed  by  the  static  physical  tests,  the  benefits  from  vanadium 
are  somewhat  similar  to  those  for  the  pearlitic  nickel  steels,  that  is,  it 
gives  a  combination  of  high  elastic  limit  and  ductility.  With  proper  heat 
treatment,  it  is  also  said  to  resist  shock,  alternate  stresses,  wear 
and  fatigue. 


596 


ALLOY  STEELS 


SECTION   VI. 

CHROME- VANADIUM   STEELS. 

Effect  of  Combining  Chromium  and  Vanadium:  In  order  that  the 
influence  of  vanadium  as  indicated  above  may  be  realized  to  the  fullest, 
the  presence  of  another  element  as  an  intensifier  is  required.  Just  as 
chromium  intensifies  the  influence  of  nickel,  so  does  it  also  stimulate 
vanadium,  but  to  a  much  greater  degree,  it  is  said,  than  with  the  former. 
Hence,  though  various  combinations  have  been  tried,  such  as  vanadium- 
nickel,  chrome-vanadium-nickel,  etc.,  the  tendency  at  present  points  to 
the  general  adoption  of  the  one  combination,  chrome-vanadium. 

Properties  and  Uses  of  Chrome- Vanadium  Steels :  The  hot  working 
of  these  steels  presents  no  difficulties,  the  steel  behaving  in  the  press  and 
rolls  much  like  the  higher  carbon  plain  steels.  In  physical  properties,  they 
are  similar  to  chrome-nickel  steel  except  that  their  contraction  of  area 
for  a  given  elastic  limit  is  a  little  greater.  They  are  also  said  to  be  more 
easily  machined  than  chrome  nickel  steel  and  are  more  free  from  surface 
defects,  such  as  scale-pits  and  seams.  While  some  enthusiasts  maintain 
that  it  is  the  steel  best  adapted  to  resist  shock  and  fatigue,  others  hold 
that  the  chrome-nickel  steel  answers  all  requirements  just  as  well.  Perhaps 
the  truth  of  the  matter  is  that,  while  both  steels  are  available  for  most 
purposes,  there  are  limited  fields  in  which  one  may  excel  the  other  and  in 
which  each  has  its  own  sphere  of  usefulness.  Most  of  the  chrome-vanadium 
steel  made  by  the  Carnegie  Steel  Company  is  used  for  driving  axles  and 
other  forgings  for  locomotives,  automobile  springs  and  axles,  compressed 
air  flasks,  torpedo  tubes,  and  gun  forgings.  They  are  nearly  always  heat 
treated  before  being  put  into  service,  but  in  some  automobiles  the  frames, 
and  even  part  of  the  forgings  and  shafts,  are  made  of  the  steel  in  its  natural 
state.  The  composition  and  properties  of  three  grades  of  this  steel  in  the 
untreated  condition  are  given  herewith. 

Table  70.    The  Composition  and  Mechanical  Properties  of 
Untreated  Chrome=Vanadium  Steels. 


COMPOSITION 


Grade 
No. 

C. 

% 

Mn. 

% 

Si. 

% 

s. 
% 

P. 

% 

V. 

% 

Cr. 

% 

Tensile 
Strength, 
Pounds 

Elastic 
Limit, 
Pounds 

Contra- 
ction of 
Area,  % 

Elonga- 
tion in  2 
Inches% 

1 
2 

3 

0.57 
.46 
.18 

0.84 
.48 
.32 

0.27 
.20 
.18 

0.04 
.03 
.03 

0.01 
.01 
.01 

0.31 
.14 
.20 

1.36 
1.17 
.74 

142,000 
125,000 
65,000 

114,000 
95,000 
47,200 

42 
55 
62 

14 
20 
23 

TENSILE  PROPERTIES 


Some  idea  of  the  general  results  obtained  from  heat  treating  the  chrome 
vanadium  steels  and  of  the  methods  employed  may  be  gained  from  the 
following  table: 


CHROME-VANADIUM  STEEL 


597 


Table  71.     Physical  Properties  of  Treated  Chrome= Vanadium  Steels. 
Tests  made  on  Small  Rolled  Sections 


CHEMICAL  COMPOSITION 

HEAT 
TREATMENT 

MINIMUM  PHYSICAL  RESULTS  AFTER 
TREATMENT 

Carbon 
PerCent. 

Manga- 
nese, 
PerCent. 

Chrome- 
ium, 
PerCent 

Vana- 
dium, 
PerCent 

Water 
Quenched, 
Deg.  C. 

Draw 
Deg.  C. 

Tensile 
Strength, 
Lbs.  per 
Sq.In. 

Elastic  Limit, 
Lbs.  per 
So.  In. 

M 

Reduction 
of  Area, 
Per  Cent. 

*.19 

.49 

.96 

.23 

850. 

749 

101,400 

91,200 

27 

69 

712 

109,500 

98,800 

24 

66 

675 

121,200 

113,100 

22 

66 

635 

129,600 

121,200 

21 

60 

596 

136,000 

125,700 

20 

60 

574 

146,900 

.  137,200 

20 

58 

*.25 

.30 

.85 

.14 

850. 

748 

88,640 

78,960 

29 

77 

697 

98,520 

92,200 

26 

72 

657 

118,700 

114,100 

24 

72 

607 

121,800 

118,200 

22 

69 

... 

574 

132,400 

125,800 

20 

64 

f.38 

.41 

.97 

.24 

815 

704  ' 

100,000 

88,000 

27 

65 

649 

118,000 

101,000 

23 

60 

593 

130,000 

108,000 

18 

52 

538 

130,000 

108,000 

16 

50 

482 

157,500 

142,000 

15 

47 

.... 

427 

177,500 

155,000 

11 

36 

Oil 

Quenched 

815 

700 

95,000 

75,000 

30 

65 

650 

117,000 

98,000 

20 

57 

595 

125,000 

105,000 

18 

56 

540 

133,000 

113,000 

18 

50 

.... 

480 

143,000 

116,000 

16 

48 



430 

149,000 

120,000 

15 

49 

Annealed 

760 

88,500 

58,000 

30 

59 

* 

As  Rolled 

127,500 

96,500 

20 

48 

*Silicon  .05%.     Phosphorus  under  .035%.     Sulphur  under  .04%. 
fSilicon  .25%.     Phosphorus  .021%.  Sulphur  .041%.    Tests  on  1"  rounds. 


WORD      INDEX 


Abrasion  tests 35 

Abramsen  straightening  machine 468 

Absolute  temperature 7 

Absorption 5 

Acetanilide 109 

Acetylene ' 69 

Acid 8-15 

Acid  anhydride 15 

Acid  Bessemer  iron 129 

"       ore 40 

Acid  Bessemer  process 172  to  194 

Acid  Bessemer  steel 187 

Acid  Flux 118 

Acid  lining  in  converter 184 

"     in  open  hearth 200 

Acid  refractory 29 

Acid  slag 123 

Adamite  rolls v 323 

Adhesion 4 

Afterblow 200 

Air  chamber  in  open  hearth 216 

Air  cooling 211-542 

Airport 213 

Alkalies 39 

Alligator  Shears 473 

Allotrimorphic  crystals 533 

Allotropy 23-528-532 

Alloy 8 

Alloy  steel 579 

Alloy  steel  ingots 362 

Alloy  treated  steel 579 

Alphairon 532 

Alternating  current 251 

Alternator 246-247-253 

Alumina 26-39 

39-41-160 

118 

Aluminum 1 1-26-166 

Ammonia 25-116 

Ammonia  gas 100-116 

Ammonia  liquor 99-116 

Ammonium  sulphate 116 

Amorphous  carbon 23 

Ampere 245-262 

Angles 462 

Angular  fracture 306 

Angular  method  of  rolling 446 

Anhydride 15-16 

Aniline 109 

Aniline  hydrochloride 109 

"     salt.. 109 


in  ores 


Annealing  steel 

box 

"  oven  (furnace) . 

temperatures . . . 
Anthracia  oils 


539 

546 

459-546 

540-541 

115 

Anthracite  coal 66-78-190-228 

Anthranilic  acid 113 

Antifriction  metal  (see  bearing  metals) ...        331 

Antimony 12 

Antipyrin 115 

Arc,  electric 264 

Arc,  furnace 261-265 

Archean  era 79 

Armor  plate 591 

Arsenic 12 

"     in  blast  furnace 166 

Ash  in  coal 75-76-80 

"    in  coke 85-160 

Aspirin 115 

Atomic  weights 11-12 

Atoms 10 

Austenite 526 

Austenitic  nickel  steel 584 

Available  base 118 

Avogadro's  hypothesis 13 

Axles,  manufacture  of 508  to  515 

Azo  benzene ...  109 


Ball  stuff 184 

Banking 159 

Bank  ovens 87 

Barium 11 

Barium  carbonate  in  case  hardening 565 

Bar  mill 474 

Base,  chemical 8 

Base  of  rail 449 

Basic  anhydride 15 

"    Bessemer  process 172 

"    flux 118 

"    open  hearth  process 198 

"    ore 40 

"    pig  iron 129 

"    process 175 

"     refractories 30 

"    slag 123 

Battery  of  coke  ovens 86 

Bauxite 31-32 

"     brick 32 

Beams 465 

Bearing  metal 331 


600 


WORD  INDEX 


Beehive  coke 86  to  90 

"       coke  oven 86 

"       process 86 

Belgian  mill 477 

"      oven 90 

Bell  and  hopper 139 

Bellypipe 134 

Bending  test 308 

Benzaldehyde 112 

...69-105  to  110 


Benzene  series 

sulphonic  acid 110 

Benzenyl  trichloride 112 

Benzidine 108-109 

Benzine 69 

Benzol 101  to  110 

"     manufacture  of 100  to  105 

"     gradesof 107 

"     usesof 107-109 

Benzoic  acid 112 

Bertrand-Thiel  process 201 

Bessemer  converter,  construction  of 183 

Henry 176 

"        ore 40 

"       iron 129 

"       steel 190 

steel  process 175 

"        (steel)  converter 183  to  186 

reactions  in 193  to  196 

Beta  iron 532 

Billet 365 

"    mill 391  to  406 

Binary  compounds 18 

Binder  in  coal 80 

Binding  material  for  refractories 29-30-31 

Birmingham  ore  district 42 

Bituminous  coal 66-78-80 

Blanks  for  wheels 497-505 

Blast  for  Bessemer  converters 180 

"     for  blast  furnace 150 

"    for  cupola 179 

"     furnace,  construction  of 131 

equipment  of 130 

foundation  of 131 

"      gas 66-71 

Bleeder 141 

Blind  pass 426 

Blister 435 

Block  of  ovens 87 

Bloom 365 

Blooming  mill 366  to  384 

Blow 187 

Blower 188 

Blowing  engine 150-180 

Blowholes...  346 


Blow  in 

Blow  off  valve 

Blowing  in  burden . . . 

Blow  pipe 

Body  of  rolls 

Boil  in  a  converter . .  . 
'  "open hearth. 

Bone  coal 

Boron 

Bosh... 


152 

143-156 

153 

134 

322 

188 

221 

80 

12 

135 

135 

"    brick 137 

"    plates 136 

"    plate  boxes 136 

Bott 134 

Bottom  blown  converter 183 

"      casting 229-324 

"      of  blast  furnace 132 

"      of  converter 185 

of  open  hearth 219 

"      pouring 228 

"      stuff 185 

Box  annealing 546 

Box  pass 323 

Boyles'  law  (see  volume  of  a  gas) 2 

Braddock  insulated  rail  joints 454 

Braddock  works  (see  Edgar  Thomson) ....  177-183 

Brasses 331 

Breaking  load 304 

Breakout  in  open  hearth 230 

Breeze,  coke 90 

Brick,  silica 29 

"     clay 30 

"      hearth  and  bosh 137-138 

"     in-wall 137-138 

"      top 137-138 

Bridge  wall 211 

Brightman  straightener 468 

Brine  for  hardening 551-552 

Brinell  tests 310-311 

"      hardness  number 310-311 

Briquettes  (or  Briquets) 66-220-242 

British  thermal  unit 7-60 

Bronze 331 

Brookville  coal  bed 79 

Brown  coal 77 

Brown  ore 36-37 

B.T.UorB.  t.  u 7-60 

Buckles  in  plates 426-435 

"      in  bars 494 

Bucket  hoist 140 

Buggy  for  Bessemer  plant 182 

'      for  open  hearth 207 

Bulkhead 211 

Bullens 517 

Bull  head  rail 437 


WORD    INDEX 


601 


Bundling  merchant  bars  
"        for  export  •  
Burdening  blast  furnace  
Burden  on  a  blast  furnace  
Burned  steel  
Bustle  pipe  
Butane  
Butterfly  method  of  rolling  
By-pass  
By-product  coke  
gas  (Cokeoven  Gas)  
plant  
process  
advantages  of  

491 
491 
159 
159 
...       495 
...        135 
70 
..   462-463 
150 
85-90  to  98 
.  .  .     66-71 
98 
90 
.   .          91 

Carbon  monoxide  in  steel  
"     steel  (see  plain  steel)  
"     in  pig  iron  
"  combined  
"  graphitic  
"  steel  
"  steel  for  case  hardening..  . 
Carbonizing  agent  
box  
materials  
mixtures  
"         pack  
Carbonless  iron  
Car  dumper 

269-518 
579 
127 
127 
127 
570 
563 
564 
564 
564 
565 
566 
518 
151 
...497  to  506 
504 
567 
562-568 
172 
152 
312 
429 
475 
77 
533 

Carnegie  Schoen  wheels  
tape  size  

Calcination  of  dolomite  
"  limestone  
"  magnesite  
Calcined  dolomite  
magnesite  
Calcining  plant  ,  
Calcite  (see  limestone)  
Calcium  
carbide  in  electric  furnace  slag 
Calcium  carbonate  
fhiroide  (seeFluorspar)  120-223- 
oxide  
silicates  
"        sulphate  
sulphide  

25 
25 
...  25-231 
32 
32 
202 
36 
.  ...     11-25 
.  .    .122-228 
.  ...   25-166 
268-270-282 
25 
123 
237 
.  .   270-287 
503 

Case  
"   hardening  
Casting  iron  
machine  
"      steel  
Castors  
Catcher 

Cellulose 

Cement  carbon 

Cementation  process  
Cementite  in  pig  iron  
"  steel  
Cenozoic  era  
Centering  for  axles  
Centigrade  
Channels  

173-562 
127 
518 
79 
511 
6-7 
463-464 
66 
324 

Caliper 

Charcoal  

.  .  .     60-61 
60-63 

"       iron  

"       intensity 

Charging  blast  furnace  
boxes  
machine  
Chemical  calculations  

156 
207 
206 
19 

Calorimeter  
Camber  in  rails  
Campbell  furnace  
H.  H  

.  .  .  .     62-63 
.  .  .  .        450 
.  .  .  .        200 
570 
201 

8-9 

compound  

8 

Carbolic  acid 

115 

equations  
formulas  
nomenclature  
"        radicals  
"        reactions,  laws  of    

13 
13 
18 
14 
17 

Carbon 

23 

'     compounds  
'     dioxide  in  Bessemer  process  .  .  . 
"  in  blast  furnace.  .  .  . 
"  in  O.  H.  process  — 
"  in  producer  gas  
in  blast  furnace  
iron  diagram  
'     monoxide  
in  Bessemer  process 
"  blast  furnace.  .  .  . 
"         "  case  hardening... 
"  electric  furnace.  . 
"  0.  H.  process.  ..  . 
"           "         "  producer  eas  — 

24 
194 
.  .  .  .  163-167 
238 
72 
.  ...        163 
....524-529 
22 
....        194 
167 
564 
.  .  .  .        286 
.  .  .  .        238 
72 

"        symbols  
Chemistry  
Chill  depth  of 

9 
3 
325 

"     test 

155 

Chilled  hearth  

158 
324-326 
324 

"      roll 

Chimneying             

158 

143 

11 

Chocks.  .  . 

...322-331 

602 


WORD  INDEX 


Chromite 26-31-32-231 

Chrome  brick v 31 

"       nickel  steel 590 

"       ore 231 

"       steel 587 

"       vanadium  steel 595 

Chromium 26 

in  blast  furnace 166 

"  steel  for  case  hardening 564 

Cinder 120 

"      cooler 134 

"      notch ' 134 

1      pitman 218 

Circular  mil 257 

Circular  shapes 497  to  507 

Clairtoncoke  plant ,  93 

Clarion  coal  bed 79 

Clay 29 

"   fire 29 

"   flint 29-138 

"    plastic 29-138 

"   brick 30 

Cleaning  plant  for  blast  furnace  gas 146 

Cleavage 533 

planes. 533 

Clinton  iron  ore 79 

Closed  pass 323 

Coal,  kinds  of 66 

"      gas 66-71 

"      tar 66-67 

Cobalt 11 

Cobble 414 

Cogging  mill 365 

Cohesion 4 

Coil,  of  hoop 473 

Coke 66-80-85-160 

"    breeze 90-98 

"    oven  Gas 66-71 

Coking  process 88 

Colby 263-576 

Cold  bend  tests 308 

"     blast 150 

"     short 233 

'     templet 439 

"     blast  valve 143 

"     working 313-459 

Collar  marks 414 

Collars  on  axles 512 

"  rolls 323 

Combination  mill 330-477 

Combination  plate 427 

Combined  carbon 127 

water 15-41 

Combining  weights 9-10 

Combustion 60 

Compression  tests 33 


Concentric  converter 183 

Conduction  of  electricity 244-256 

"  heat 59 

Conductors  of  electricity 245 

Confining  die 460 

Congo  red 114 

Coning  of  wheels 504 

Constitutional  diagram 585-588-595 

Continuous  coil 473 

"         furnace 421 

mill 397  to  405 

Contraction  of  area  (see  reduction  of  area)       307 

of  ingots 343 

tests 34 

Convection  of  heat 59 

Converter 183-186 

"       reactions 193-197 

Cooling  bed 479 

for  annealing 543 

"  hardening 551 

"  tempering 557 

Cope i.        324 

Copper.' 12 

'     bearing  steel 576 

"     effects  on  steel 576 

"     in  blast  furnace 166 

"     in  bearing  metal 331 

Corrosion  of  steel 577 

Cort,  Henry 318 

Cotton  seed  oil 553 

Cotton  tie 472-49«5 

Coulomb 245 

Coupling  box 318-322-330-334 

Covington  drawing  machine 90 

Cracks  in  billets  and  blooms 417 

"       "  ingots 349 

Cresole 115 

Critical  points 527 

"      range 527 

Cross  country  mill 330-479 

Crucible  of  blast  furnace 132 

"       steel 174 

Crude  still 102 

Cryohydrate 522 

Crystals 533 

Crystallization 5-348 

of  steel 533 

water  of 15 

Cup  and  cone 139 

Cupola 179 

"      charge 178-204 

Cupped  fracture 306 

Cutting  axles 511 

"      rails 450 

"       shapes 466-468 

Cuyuna  ore  range 47 


WORD  INDEX 


603 


Dalton 

Debenzolating  tower .... 

Decalescence 

Decane 

Deep  seated  blow  holes. . 


10 
100 
527 

70 
346 


Defects  in  semi-finished  material 413  to  417 

Definite  proportions,  law  of 9 

Deformed  bars 469 

Deliquescent  substance 16 

Delta  connections 255 

Dendrite 533 

Density 4-34 

Deoxidation  of  Bessemer  steel 190-197 

in  electric  furnace 269-286 

Dephosphorizing  slag 270 

Destructive  distillation 85 

Desulphurizing 269-286 

Detinned  scrap 577 

Diagonal  method  of  rolling 447-465 

Diamond,  form  of  carbon 23 

pass 323 

Di-basicacid 19 

Die  for  punching  rail  joints 459 

Differential  hardening 553 

Diffusion 5 

Dilation  of  steel 530 

Dimethylaniline 112 

Diphenylamine 112 

Direct  current 253 

'     process,  Siemens 199 

Discard 343-498-509 

Divided  circuit 258 

Dolomite 26-31-32-119-230 

Double  acting  hammer 315 

annealing 546 

"      bell  and  hopper 139 

Down  comer 141 

"     take 141 

Drag-over  mill ^. 330 

Draught 339-381 

Drawing  coke 89 

Dressing  rolls 329 

Drill  tests  for  ore 47 

(See  drill  exploration) 
Drop  bottom 179 

"     forging 318 

"     tests 309-515 

Dry  bases  of  analysis ' 41 

Dry  blast 150 

Dry  chemistry 15 

Drying  Bessemer  bottoms 186 

blast  furnace 152 

"      O.H.  furnace 218 

Ductility ...  5 


Duquesne  Works 368 

rail  joint 453-455 

gas  cleaning  plant 147 

Duplex  process 293  to  297 

"     slag 297 

Dust  catcher 146 

Dynamic  stress 301 

Dynamo 250 

Dyne 243 

Eccentric  converter 180 

Edgar  Thomson  mills 447 

splice  bar  shop 458 

works 180 

Edging  pass 462-468-471 

Efflorescence 15 

Effusion 5 

Elastic  deformation 304 

"      limit 303-307 

Elasticity 4 

Electric  arc 264 

"  furnaces 265 

current 246  to  256 

furnace  slag 208 

furnaces 261  to  267 

"      heating 262  to  267 

pyrometers ^ 64-65 

"      steel,  properties  of 289  to  291 

"      steel,  uses  of 291 

Electrical  resistance  pyrometer 64 

Electrodes 277-279 

Electrolysis 14-261 

Electrolytes 8 

Electro  magnetic  induction 249-250 

Electromotive  force 246 

Electron  (theory) 13 

Element,  chemical 

Elongation,  per  cent,  of 301-307 

Empirical  formula 68-69 

Endothermic  reaction 8-16 

Energy 5-243 

'     kinds  of 

"     laws  of 6 

Erg 244 

Ethane 70 

Ether 

Ethylbenzene 105-106 

Ethylene 69 

Eutectic  alloy 348-523 

Eutectoid 525 

"       steel 525-527 

Exothermic  reaction 8-16 

Expansion  tests 

Exploration  for  iron  ore 47 

Explosion  doors 141 

Extension * 


604 


WORD  INDEX 


Fahrenheit  scale 

Falling  weight  test  (see  drop  test) . 

Fatigue  stress 

Feldspar 

Ferric  oxide 

Ferrite. . . 


174 
7 

309 

301 
29-36 
22-36 

518 


"     in  pig  iron  ......................  127-524 

"      "steel  ....................  •  .....  518-524 

Ferro  chromium  .......................        228 

"     manganese  ...................  129-190-228 

"     phosphorus  ......................        228 

"     silicon  .......................  129-190-228 

"     vanadium  .......................        228 

Ferroso-ferric  oxide  .....................     22-36 

Ferrous  and  ferric  compounds  ...........         27 

"      compounds  ....................         27 

oxide  in  open  hearth  ............       234 

products  ......................        169 

"      sulphate  .......................         27 

Fibrous  structure  ......................        170 

Fillet  .................................       408 

Fin  ..................................  336-494 

Finish  on  bars  .........................  489-495 

Finished  products  ......................  418-515 

Finisher  (see  finishing  stand)  ............        337 

Finishing  period  in  0.  H.  process  ........        270 

"        rails  .........................  450-452 

rolls  .........................        337 

splice  bars  ....................        452 

stand  ........................       337 

steel  .........................  190-226 

"        temperature  ..................  313-450 

Firebrick  .............................         32 

"    clay  ..............................         32 

"   clay  brick  .........................         32 

"    cracks  on  rolls  .....................        495 

"    damp  ............................         69 

Firestone  .............................        185 

First  helper  ...........................        218 

Fish  oil  for  hardening  ..................        552 

Fixed  carbon  ..........................     76-85 

Fixed  converter  ........................        183 

Flame  in  converter  .....................        188 

"      "  open  hearth  ...................        220 

Flare  on  hoop  .........................        473 

Flats,  finish  of  .........................        489 

"     rolling  of  .........................     468 

Floors  in  open  hearth  ...................        209 

Flue  dust  .............................  38-146 

Fluid  compression  ...................... 

Fireclay  ..............................          29 

Fluor  spar  .....................  120-223-268-270 

Fluorine.  .  .  12 


Flushing  cinder  (see  tapping  slag) 122 

tar 

Flux 

"  in  the  electric  furnaces 

Flying  shear 

Foot-pound 

Force 

Forge  iron 

Forging 

axles 

"      hammer 

"      press ' 


wheel  blanks 

Former  bar 

Foundry  iron 

Four  pass  stove 

Fracture  tests  at  blast  furnace . 
"  open  hearth.. 

Fractures  of  steel 

Free  cementite . .  . 


....  98-99 
117 

....   271 
....   404 
244 
243 
129 

....316-318 
...   508-510 
316 
....        317 

495 
499 
512 
129 
142 
155 
....  224 

305-537 

520-526 

"    ferrite 520-526 

Freezing  of  alloys 521  to  526 

Frick  Coke  Company 86 

"     Furnace 264 

Frothing  slag  (see  run  off) 222 

Fuels 58  to  116 

"    for  open  hearth 203 

Fuel  oil 69 

Full  annealing 540 

Fume  from  converter 193 

Furnace  cooling 459-545 

lines 137 

Fusion  tests 33 

Gag 451 

Gag  press 451 

Gallium 11 

Gamma  iron 532 

Gangue .• 39 

Canister 29 

"      brick 29-32 

Gas 2 

"  holes  (see  blow  holes) 346 

"  port... 211 

"  producer 71  to  75 

"  volume,  laws  of 2 

"  washer 148 

Gaseous  fuels 70  to  75 

Gasoline 69 

Gayley  dry  blast 150 

Generalized  formula 68-69 

Generator,  electric 250 

Girod  furnace 266 

Glucinum ...  1 1 


WORD  INDEX 


605 


Gob 

86 

Heat  of  vaporization 

59 

Goethite 

37 

"   reactions  in  blast  furnace 

163-164 

Gogebic  iron  range 

43 

"        "         "  converter  

194 

Gold 

11 

"   treating,  axles  .-  

513-515 

Gold-silver  alloys  

521 
135 

"      car  wheels  
"          "      rail  joints 

506 
459  to  461 

323 

'  '   treatment 

539  to  568 

55 

"  units                         

7 

Grains  
Gram  

533-538 
4 

Heater  
Heating  furnace  

336-362 
...419  to  422 

"    calorie  (see  small  calorie) 

7 

"         "      cinder  

419-421 

"    molecular  volume 

13-21 

102 

"      weight 

21-61 

448 

Granulated  slag 

152 

Helix 

247 

Granulating  pit. 

152 

Helical  Pinions 

334 

Granulation  of  steel     .  . 

534 

Hematite 

36 

Graphite  ...    .           

....23-31-32 

Heptane      ....                 

.   ...         70 

Graphitic  carbon  
Gravitation,  law  of  

127 
4 

Heroult  furnace  
Hexagon,  rolling  of  

266-275 
469 

Gray  iron  

127 

Hexane  

70 

264 

High  carbon  steel 

226 

Grizzley  bar 

98 

Hiorth  furnace 

264 

Gronwall  furnace 

266 

Hoist  for  blast  furnace 

14D 

Grooved  roll 

323 

Holley,  Alexander                  

177 

Grooves  in  rolls 

323 

Hollow  boring  for  axles        

513 

Guard 

334 

Homogeneous  substance  

8 

Guide 

334-475 

Hooke's  law  

4 

"    rounds 

467 

Hoop 

470 

"    marks 

415 

473 

"    mill                                \ 

.     330-475 

470 

Gun  brick 

94 

470  to  473 

"    for  blast  furnace  

155 

139 

Half  cup  fracture  *.  

306 

244 

Hammer  forging  

316 

Hot  blast 

150 

"       steam                      

316 

135 

317 

143 

Hand  guide  mill  

475 

Hot  iron 

127-171 

"     mill  

330-474 

221 

"     round  

467 

313 

Harden  furnace 

264 

450-466-468 

HarHfning  P.arbnn 

533 

176 

"         process  of 

548 

158 

Hardness  

5 

"   templet  

441 

311 

"   top  mould  

346 

"       test 

309 

"   worked  splice  bars  

...        460 

Head  of  rails 

440 

"   working  

...313  to  321 

"       "  water 

245 

2-332-368-378 

Hearth  brick 

137 

....333-370 

"      jacket 

132 

"         top                                        .    . 

333-370 

"      of  blast  furnace 

"   132 

Howard  Axle  Works                    .   . 

..508  to  515 

"      of  open  hearth 

210 

73 

"      and  bosh  brick  

137-138 

222 

Heat  
"   cracks  in  rolls  

6 
495 

Hydraulic  press  (see  forging  press)  . 

318 
245 

"   of  formation  

60 

„ 

245 

Heat  of  fusion  

59 

Hydrocarbon  .  .  . 

24 

GOG 


WORD  INDEX 


Hydrochloric  acid 21 

Hydrogen 12-22 

Hydroquinol 109 

Hydroxide : 19 

Hygroscopic 16 

Hyper-eutectoid  steel 526 

Hypochlorous  acid 18 

Hypo-eutectoid  steel 526 

Hysteresis 530 

Idiomorphic  crystals 533 

Ignition  point  (see  kindling  temperature) .          70 

Impact  stress 301 

"      test 34-309 

Impedance 259 

Impenetrability 4 

Impurities  in  steel 518 

Incipient  crack 508 

Indigo 113 

Inductance 259 

Induction  furnace 263 

Inertia 3 

Ingot 342 

Ingot  defects. . .  '. 342  to  351 

"     mould 182-205 

Ingotism 348 

Inorganic  chemistry 8  to  27 

Inspection 417-430-451-493-498-504-509 

department 493 

of  merchant  mill  products . .  .  493  to  495 

"plates 430 

"rails 451 

"  semi-finished  products 417 

"wheels 504 

Insulator 245 

Invar 582 

Inwall 136-137 

"     brick 137-138 

Iodine 12 

Ions 14 

Iron 12-27-125 

"  action  in  the  converter 194 

"  carbonate 27-36-37 

"  early  history  of 125 

1  notch 132 

"  ore 36 

"  oxides 36 

"  oxides  in  open  hearth 232 

"  pyrites 36 

"  silicates 36 

"  sulphates 27 

"  sulphides 36-39 

Irregular  fracture 306 

Isomeric  compounds 105 


Jacket 

Jones,  W.  R.. 


132 

177 


Joule 244-245 

Journal 512 

Jump  roll :    a  plain  roll  wi  th  collars  on  each 
end.    Used  in  rolling  flats.  

Kaolin  (see  clay) 29 

Keeper,  one  in  charge  of  a  blast  furnace .  .    ' 

Keller  furnace ' 266 

Kelly,  Wm 176 

Kerosene 69 

Kidney  ore 37 

Kilogram 4 

"       meter 244 

Kilometer 4 

Kilowatt 244 

hour 244-262 

Kindling  temperature  of  gases 70 

Kinks 494 

Kish,  graphite-like  substance  given  off  by 

pig  iron 

Kjellin  furnace 263 

Koppers  by-product  coke  oven 93 

Laboratory  tests  on  fuels 62 

"  refractories 33 

Ladle,  steel 204 

"    additions 190-226 

"    reactions 191 

"    test  (see  sampling) 192-229 

Lag  (see  hysteresis). 530 

Lake  Superior  ore 79 

"         "         "  district 42 

Lamination : 435 

Lap 336-494 

Lard  oil  in  quenching 552 

Large  calorie 7 

Larry 86-97 

Latent  heat 59 

Lauth.B.  C .....  423 

"     mill 423 

Law  of  constancy  of  nature 15 

"  definite  proportions 9 

"     "ebulition 59 

"  evaporation 59 

"     "fusion 59 

"     "  heat  exchange 58 

'     "  mass  action 4 

'     "  multiple  proportions 10 

Lead 11 

"    bath,  quenching ' 552 

"    hardening  (sse  quenching  in  lead) 552 

"    tempering 557 

Lead-tin  alloy 523 

Leading  spindle 333 

Leg  pipe 135 

Lenz's  law 250 

Leveling  in  coke  oven 88 


WORK  INDEX 


607 


Liberty  mill  
Liftin"  table 

425 
335-380 

Malleability  . 

5 

Manganese  
in  converter  
in  steel  

..11-27-128-176-235 
194 
570 

Light  oil 

101-102-115 

'     rails  
Lignite  
Lime  

452 
66-77 
30-39 
223 

"         sulphide 

98fi 

in  steel  for  case  hardening  563 
Manipulator                                                     873 

"   boil  

"    cooling  

545 

Mantle  of  blast  furnace 

136 

Limestone 

25 

Marquette  ore  range  
Marsh  gas  
Martensite 

43 
69 
526-549-550-553-558 
584 

"        analysis  of 

120-160 

"        as  a  flux 

119 

in  blast  furnace  
in  open  hearth  
Limiting  angle  of  rolling  
Limnite  
Limonite  

160-170 
223-239 
340 
37 
36-37 

Martensitic  nickel  ste°l 

Martin  Brothers 

201 

"      process 

201 

Mass  
"    action,  law  of  
Massive  pearlite  

4 
17 
544 

Liner  

332 

Lining  of  blast  furnace 

137 

Matrix 

585 

"  converter  
"  electric  furnace  
Linseed  oil,  quenching  
Liquid  
Lithium  
Locus  of  a  point  

184 
275 
551 
2 
11 
521 

Matter... 

2 

"     classes  of 

2 

'     conservation  of  
'     sciences  of  
"     Btatesof  
Matthews  and  Stagg  

2 
3 
2 
551 

Lodestone  (see  magnetite)  

36 

90 

Maximum  load 

304 

"         stress 

304 

test  piece 

434 

Mayari  steel   

591 

Looping  mill 

330-477 

Mechanical  mixture  
properties  
Medium  carbon  steel  
Melter 

..-  8 
....299-301-303-304 
226 
218 

Lorry  (see  larry) 

97 
245 
226 
79 
79 

Loss  in  head                              .   .  . 

Lower  Freeport  coal  bed  

Menominee  ore  range 

43 

Merchant  bar  ...    . 

173 

182 

mill  
Mercury  

474-482 

38 

11 

Lute 

97 

aa  quenching  agent  . 
Metadihydroxylbenzene  .... 
Metal  

551 
110 
9 

Machine  cast  pig  
Macroscopic  structure  
Macro-structure  
Magascopic  (see  macroscopic)  
Magnesia  
Magnesian  limestone  (see  dolomite) 

152 
518 
518 
518 
.  .  25-30-39-166 
26-31-119-231 
25-32-228-231 
11-25 
247 
247 
247 
248 
27-36-37 
248 

Metalloid 

9 

Metallurgy 

2 

Metasilicic  acid 

123 

Metaxylene  
Metcalf's  Experiment  
Meter  

...105-106 
537 
4 

Methane 

69-70 

Magnet 

Metric  system 

4 

Magnetic  fields  
flux  
induction  
iron  ore  (see  magnetite)  . 

Micro  structure 

518 

Microscopic  structure  
Middle  Kittanning  
Mil 

518 
79 

256 

"  foot 

257 

„ 

247 

Mill,  classes  of 

365 

246 

"     shoe 

322-332 

Magnetite 

27-36 

Milling  pit  
system  of  mining  ore 
Mineral  

52 
50-52 

218 

172 

36 

"        cast  iron... 

172 

"      oil  in  quenching  

551 

608 


WORD  INDEX 


Missabe  ore  range 46 

Mixer 181-204 

Modolus  of  elasticity 301-307 

Molds  for  ingots 182-205 

Molecule 2 

"  of  elements 13 

Molecular  weight 19 

Molten  metal  (see  hot  metal) 221 

Molybdenum 11 

Monell  charge 219 

"  process 201 

Monkey  for  blast  furnace 134 

"  cooler 134 

Morgan,  C.  H 397 

"  mill 397 

Mothballs 113 

Motor  Benzol 107 

Mother  liquor 100-521 

"  metal 525 

Moulds  for  ingots 182-205 

Muck  bar 173 

Multiple  proportions 9 

Muriatic  acid  (see  hydrochloric  acid) 21 

Mushet.R 176 


Naphtha 69-101-105-111 

Naphthalene 101-113-114 

Naphthionic  acid 114 

Naphthol 114 

Nascent  state 13 

Natural  gas 66-71 

Neck  of  a  roll 322 

Necking  of  test  piece 305 

Neutral  flux 120 

refractories 31 

"      substance  (see  salt) 8 

Nickel 11-228 

"     steel 580 

"     in  steel  for  case  hardening 563 

Nickel-Chrome  steel 590 

Nigger  heads  in  open  hearth 224 

Ninety  per  cent,  benzol 103-107 

Nitric  acid 25 

Nitro  benzene 109 

Nitrogen 12-25 

in  blast  furnace 165 

Nitronaphthalene 114 

Nitrotoluene 112 

Nodulizing  (see  spheroidizing) 547 

Nomenclature 18 

Non  Bessemer  ore 40 

"    coking  coal 80 

"    electrolyte 8-9 

"    metal 9 

Normalize 547 

Nose  of  converter ...  183 


Occlusion  see  absorption) 5 

Octane 70 

Offtakes 140 

Ohm 245-257-262 

Ohm's  law 256 

Oil  and  tar  burner 68 

"  hardened  (see  oil  quenched) 551-552-553 

"  scrubbers 101 

"  temper  (see  also  oil  quenched) 551-558 

"  of  vitrol  (see  HaSOi) 23 

One  level  type  of  open  hearth 209 

Open  hearth 209 

"    process 198-242 

"    slag 122-234-242 

"    steel,  making  of 198-242 

"     pass 323 

"     pit 48-50 

"      "  mining 50 

"     top  blast  furnace 139 

Optical  pyrometer 65 

Ore 36 

"  analysis  of 160 

"  boil 222 

"  bridge 151 

"  composition  of 36-37 

"  down 224 

"  grading  of 55 

"  transportation  of 56 

"  valuation  of 38 

Orientation 533 

Orthosilicic  acid 123 

Ortho  xylene 105-106 

Oval  groove 467 

Overblown  steel 575 

Overburden 53 

Oxidation 16 

Oxide 16 

Oxygen 12-22 

'*     in  blast  furnace 162 

"    in  the  electric  furnace 268-269 

575 


Palaeozoic  era 79 

P  and  A  tar  extractor 99 

Parabenzene  sulphonic  acid 110 

Paraffin  wax 69 

Paraxylene 105-106 

Pass  in  rolling 323-337 

Pass-over  mill  (see  pull-over  mill) 330 

Pass  templet 441 

Pearlite 127-520-525 

"     in  pig  iron 127-524 

"     in  steel 519-523-526 

Pearlitic  chrome  steel 588 

nickel  steel 584 

Peat...  .     66-77 


WORD  INDEX 


609 


Pen  stock 135 

Pentane 70 

Permanent  magnet 247 

set 303 

Petroleum 66-68 

Phase  of  electric  current 253 

"      "  pearlite 543 

Phenylhydracine 108 

Phenol 110 

Phosphoric  acid 25 

Phosphoretic  steel 574 

Phosphorus 12-25 

"         in  blast  furnace 165 

"          "  electric  furnace 268 

"  open  hearth 237 

"  ore 40 

"  pig  iron 129 

"steel 573 

Phthalic  acid 114 

Phthalimide 113 

Physical  change 8 

properties 3 

"      of  plates 433 

testing  of  steel 300 

Picric  acid 110 

Pickling  test 495 

Pig  and  ore  process 199 

"  scrap  process 201 

"  casting  machine 152 

"  iron,  composition  of 127-174-228 

"  nickel .\  228 

Pigging  up 224 

Piling,  rolling  of 465 

Pillaring 158 

Pinions 322-333-369-378 

"     housings 333 

Pipe 343  to  346-495 

"  in  axles 508-512 

Pit  annealing v 545 

"  casting 324 

Pitch  for  rolls '. 382 

"    line 328 

Pittsburgh  coal  bed 79 

Plain  steel 579 

Planishing  pass 337 

rolls 337 

Plastic  clay 29 

'     deformation 305 

Plasticity 5 

Plate  mills 423-435 

Plates,  kindsof 423 

"      rolling  of 423-425-428 

Platinite 582 

Platinum 11 

Pneumatic  process 175 

Poling 192 

Polyphase  currents,  electric 253 


Pony  roughing  stand 337 


Porosity  

4 

Potash  (K20)  

20 

Potassium  

....   12-166 

Potential  

....        243 

Pouring  (see  teeming)  

....  192-228 

Powdered  coal  

81 

Power  

....        244 

"    factor  

....        259 

Preliminary  test  

....        287 

Press,  forging  

317 

Pressing  (see  forging)  

317 

Primary  austenite  

525 

Prismatic  sulphur  

23 

Producer  

71 

"      gas  

....     66-71 

Progressive  distillation  analysis  

....     75-76 

"         hardening  

....       553 

Propane  

70 

Properties  of  matter  

3 

Prospecting  for  ore  

47 

Proximate  analysis  

....     75-76 

Puddle  bar  (see  muck  bar)  

173 

"      iron  (see  wrought  iron)  

....        173 

Pulling  test  

....       301 

Pull-over  mill  

330 

Pulpit  

179 

Pulverized  coal  (see  powdered  coal)  .  . 

.  .  .  .81-82-83 

"   burner  

84 

Punching  splice  bars  

....        459 

Purification  processes  

175 

Pyro-chemical  process  

128 

Pyrometers  

64 

Quartz  

....     24-36 

Quenching  

548-551 

bath  

552 

"        media  

552 

"        tank  

514 

Quicklime  (see  calcium  oxide)  

25 

Quick  silver  (see  mercury)  

11 

Rabble  

230 

Radiation  

59 

"       pyrometer  

65 

Radical  

14 

Ragging  

340 

marks  

415 

Rail,  evolution  of  

437 

"     joints,  rolling  of  

454 

"         "     treatment  of    

459 

"        "     types  of  

.....453-454 

"     mills  

..442  to  449 

"    rolling  of  

..448  to  452 

"     steel,  Bessemer  

190 

610 


WORD  INDEX 


Raisers 53 

Raw  materials  (see  basic  materials) 58 

Reactions,  chemical 13 

"         in  blast  furnace 163-171 

Reaumur 7 

Recalescence 527 

Recarbonizing  (see  recarburizing) 191-226 

Recarburizing,  Bessemer  steel 191 

open  hearth  steel 226 

Recuperative  furnace 421-422 

principle 63 

Red  ore 36 

"    short  (see  hot  short) 176 

Redstone  coal  bed 79 

Reduction 16 

of  area 301-307 

Refractories 28 

Regenerative  chambers 212-217 

furnace 419 

principle 63 

Reheating  furnace 419  to  422 

Repeater 330-479 

Repeating  mill 330 

Rephosphorization 226-298 

Rerun  benzol : 103-104 

"      toluol 104 

Resorcinol 110 

Residual  manganese 191 

Resiliency 575 

Resistance,  electrical 256 

"          furnace 263 

"          pyrometer 64 

Resting  period 302 

Retardation 527 

Retention  theory 555 

Retort  coke  (sse  by-product  coke) 85  to  98 

oven  (330  by-product  coke) 93 

Reverberatory  furnace 420 

Reversing  mill 330-366-367-368-369 

Rhombic  sulphur 23 

Roasting  (see  calcining) 25 

Roll  bearings 331-371 

"    design  for  billet  mills 394-402 

"       "  blooming  mills        373-377-379-383 

"        "       "  merchant  mills 482 

"       "  rails 438-447 

"        "     general  remarks 327 

"     how  to  study 438 

"    marks 495 

"    size  of 327-384 

"    table 335 

"    tables 322 

Rolling  defects 413-494 

history  of 318 

"      principles  of 319-321 


Rolls 322  to  331 

"    for  billet  mills 393-400-402 

"      "  blooming  mills 371-377-379-383 

Roof  of  open  hearth 211 

Rotary  shears 429 

Rough  surface,  cause  of 415 

turning  axles 512 

Roughing  passes 444-450-483-484 

stand 477 

rolls 337-423-444-416 

Rounds,  kinds 467 

rolling  of 467 

"       straightening  of 468 

Run  off  slag 222 

Run-of-mine  coal 86 

Runners 141-155 

Running  stopper 205 

Saccharin 112 

Sack's  mill 331 

Salamander 132 

Salt 8 

Salt  and  ice 522 

Salicylic  acid 115 

Sampling  pig  iron 155 

"       Bteel 192-229 

Sand 32 

"    as  a  flux 118 

"    as  a  refractory 29 

"    bottom  furnace 419 

"    roUV 323 

"    seal 514 

"    test 155 

Sandstone  (a  sedimentary  rock) 

Saturated  solution 522 

Sauveur 517 

Scabs 349-415 

Scaffolding 158 

Scale .,..' 233 

Scarf 538 

Schedule  for  merchant  mills 482-485 

Schoen,  Chas.  E 497 

"       mill 331-500 

Scleroscope 309 

Scramming 50-53 

Scrap  and  pig  process 201-219 

"     in  Bessemer  process 188 

"     in  open  hearth  process 201-219 

Screw  down 333 

"      steel 190 

"      stock 190-572 

Scull  (see  skull) 225 

Seams,  cause  of 346-415 

"      in  bars 494 

in  blooms,  billets,  etc 415 

"      in  rails 452 

Second  helper 218 


WORD  INDEX 


611 


Second  strand 337-485 

Section  mill  (see  shape  mill) 461 

Segercone 33 

Segregated  cementite 544 

Segregation 348 

in  axles 508-512 

Selective  freezing 524 

Selenium 12 

Self-fluxing  ore 117 

"  inductance 259 

Semi-continuous  mill 477 

"  finished  products 364  to  414 

Sensible  heat 58 

Sesquioxide  base 124 

Seventy- two  hour  coke 87 

Sewickley  coal  bed 79 

Shaft  of  blast  furnace  (see  stack) 136 

Shakedown 225 

Shape  mill 461 

Shaped  bloom 463 

Shear  foreman 490 

"  steel 174 

Sheared  plate  mill 423 

Shearing  defects 415 

"  forces ! 301 

...429-433 


301 

Shears  for  blooming  mill 372 

Sheet  bar 190-408 

"mill 408-413 

"rollingof 406to413 

Shoe  of  a  mill 322-332 

Shore  scleroscope 309 

Shrinkage  of  steel  in  ingot 343 

Side  blown  converter 183 

Side  shears 429 

Siderite 37 

Siemens,  William. 

Siemen's  direct  process 199 

"       furnace 199 

"       pig  and  ore  process 201 

pyrometer  (see  water  pyrometer)         64 

steel  (see  open  hearth  steel) 198 

Siemens-Martin  process 201 

Silica 24-39 

"    brick 29 

"    in  Bessemer  process 

"    "  blast  furnace 165 

"    "  open  hearth  process 234 


••  "sand 32 

Silicate 121-123 

Silicon,  acids  of . .  jf 

"      in  converter 

"       "  open  hearth  process 

"       "pig  iron 24-127-129-171 


Silicon  in  steel  for  case  hardening 

Silico-spiegel.  . 

Silver 

Simple  steel 

Sine  curve 

Single  coil  of  hoop 


5C3 

129 
12 
579 
252 
473 


'     level  open  hearth  (see  one-level)  .  .  .        209 
"     phase  current  ....................     252-3 

Sinkhead  .............................  206-324 

Sintering  ..............................        219 

Skelp  .................................        190 

Skew'back  ............................       211 

"     brick  ..............  ..............        211 

"     channels  ........................        211 

Skewed  rolls  ...........................       404 

Skimmer  ..............................        279 

Skin  of  ingot  ..........................        343 

Skip  hoist  .............................        140 

Skull  .................................       225 

Slab  ..................................        365 

"  rolling  of  .......................  385  to  390 

Slab-and-edging  method  of  rolling  flats  ...        468 

"      "        "    rails  438  to  449 

Slabbing  mill  .......................  385  to  388 

Slaked  or  Slacked  lime  (CaO+H20)  ........ 

Slag  ...............................  15-120-152 

"  in  Bessemer  process  ................       122 

"    "blastfurnace  ....................        121 

"    "  electric  process  ..................  122-288 

"  functions  of  ........................        120 

"  hole  ..............................       210 

"  notch  (see  cinder  notch)  ............       134 

"  in  open  hearth  process  ...........  122-234-242 

"  pockets  ...........................        211 

Slagging  tests  .........................         34 

Sleevebrick  ...........................       205 

Slicing,  system  of  mining  ...............         53 

Slips  .................................        157 

Slivers  ................................  41M94 

Sloppy  heat  ........................... 

Slurry  .................  ...............        138 

Small  calorie  ..........................  7 

Smelt  ................................       H7 

Snake  ................................       435 

Snort  valve  ...........................        150 

Soaking  ingots  ........................  359-362 

»       pit  ...........................  342-352 

"       "efficiency  of  .................       362 

Soda  (same  as  sodium  oxide)  ................ 

(also  sodium  carbonate)  .................. 

Sodium  ...............................  H-166 

Soft  steel  (see  low  carbon  steel)  ..........       226 

Solid  ................................. 

"    solution  ..........................  519-521 


612 


WORD  INDEX 


Solute,  dissolving  substance 

Solution 8 

Solvent,  substance  dissolved '. 

naphtha 113 

Sorbite 543-559 

Sorbitic  steel 543 

Spalling  test 35 

Spanner  bar 432 

41       block 432 

Spar  (see  fluor  spar) 120 

Spawling  tests  (see  epalling  tests) 35 

Special  steel 579 

Specific  gravity '       5 

"      heat 58 

"    pyrometer 64 

"       resistance 257 

Speed  in  rolling 339 

Spheroidize 547 

Spiegel 129-190-228 

"     cupolas 180-204 

Spindle 322-334-369-378 

Splasher 132 

Splice  bar 453-461 

"        "analysis  of 190 

"  finishing  of 458 

"  rolling  of 454 

Spoon 225 

Spout  of  open  hearth 210 

Spread  in  rolling 319-328 

Spring  heat  (spring  steel  heat) 

Square  mil 257 

Stack  of  blast  furnace 136 

"     "  open  hearth  furnace 217 

Standofrolls 322 

Standard  ferro 129 

Standards  (see  housings) 322 

Star  connections 255 

Stassano  furnace 265 

Static  stress 301 

Stationary  furnace  (one  not  movable) 

Stead 533 

Steam  shovel  mining 48-50 

Steel 173 

"  ladle 204 

"  rolls 323-326 

"  spout 210 

"  tie,  rolling  of 465 

Sticker 224 

Stock  distributor 140 

"    house 151 

"    indicator 140 

"    line 133 

"    pile  (see  ore  pile) 131-150-151 

"    yard 131-207 

Stone  (see  limestone) 25 

Stool...  182 


Stopper 182-205 

Stove  burners 143 

"     linings 145 

"     valves 143 

Stoves,  kinds  of 142 

Straightening  axles 511 

bars 492 

machine 427-468-492 

plates 427-433 

press 451-511 

rails 451 

rolls 427 

rounds 468 

shapes 466 

Strain 5 

Strand 337 

Stratified  structure 519 

Straw  oil 101 

Stress 5 

"    kinds  of 301 

Stretch  (see  elongation) 301-307 

Strip 470 

Stripper 181-205 

Stripping 50-51 

Structural  formula 68-69 

shapes,  rolling  of 461  to  469 

steel,  testing  of 301 

Subcutaneous  blow  holes  (see  blow  holes 

near  the  skin) 346 

Substance : 2 

S-ulphanilic  acid 112 

Sulphates  (see  salts  of  sulphuric  acid) ....  27-116 

Sulphides 18 

Sulphur 12-23 

in  Bessemer  process 175 

"  blast  furnace 165-171 

"open  hearth 236 


"  pig  iron — 

Sulphuric  acid 

Sulphurous  acid 

Superficial  hardening . . 
Surface  defects . . . 


128 

23 

19 

568 

.413-435-451-494-504 

Surface  hardening  (see  case  hardening) ...  562 

Sweat 221 

Swedish  Bessemer  process 176 

"      iron 176 

Sweep 324 

Symbols,  chemical 9 

Synthesis 16 

Table,  of  a  tee  shape 466 

Tables,  of  a  mill V. 335 

Talbot  furnace 294 

process 201 

Tandem  mill  (see  Belgian  mill) 477 


WORD  INDEX 


613 


Tap  a  heat  (see  tapping  furnace) 154-225 

Tap  hole,  blast  furnace 132 

"        "  open  hearth  furnace 210 

Tape  size 504 

Tapping,  blast  furnace 154 

"        electric  furnace 281 

hole 132-210 

"        open  hearth  furnace 225 

rod 225 

slag  (see  basic  slag) 122 

Tar 99-114 

"  as  a  fuel 67 

"  burner 68 

"  extractor 99 

"  refmementof 114 

•'  uses  of 115 

Teaming  (same  as  teeming) 192-228 

Teerail 436 

"    rolling  of 466 

Teeming,  Bessemer  steel 192 

electric  steel 281 

"        ladle 182 

open  hearth  steel 228 

Temper  colors 556 

Temperature 6 

"          tests  in  open  hearth 225 

Tempering 554 

austenic  steel 558 

"        martensitic  steel 558 

troostitic  steel 558 

Templet 439-440-441-442 

Temporary  magnet 248 

Tenacity  (see  tensile  strength) 301 

Tensile  strength 301-307 

Tensional  stresses 301 

Terminology 18-19 

Ternary  compounds 18 

"       steels 580-584-587-595 

Test  Mould.   .; 229 

Test  piece „ 302-309 

1 224-225 

515 

...303-309 
33 

.299  to  311 
149 
58 

.527  to  533 
64 
64 
6-7 
...175-177 


spoon. 

Testing  axles 

machine 

refractories 

"      steel 

Theiscn's  cleaner 

Thermal  capacity 

critical  points 

Thermo-  electric  couple 

pyrometer .... 

Thermometer 

Thomas-Gilchrist  process . 


Three-high  blooming  mill 377  to  384 

"  mill 330 

"  pass  stove 142 

"  phase  current 253-255 

Ties,  rolling  of 464 


Tilt  hammer 316 

Tilting  converter 183 

"      furnace 200-294 

"      table 335 

Tin II 

"  insteel 577 

Titania  (Ti02) 166 

Titanium 12-165 

T.N.T Ill 

Tolerance,  reasons  for!90-226-329-348-428-430-467 

Toluene Ill 

sulphonic  acid 112 

Toluidin 112 

Toluol 101-105-106-111-112-113 

Tongue  and  groove  pass 406 

Top  brick 137-138 

"    of  blast  furnace 139-141 

Torsional  stresses 301 

test 308 

Total  carbon 127 

Toughening 559 

Trade  heat 219 

Trainof  rolls 477 

Transformation  range  (see  critical  range)  527 

Transformer 260 

Transporting  ores 56 

Tri-basic  acid 19 

Trinitrotoluol  (T.  N.  T.) Ill 

Triplex  process 297 

Troostite. 550-556 

True  annealing 540 

Trunnel  head 87 

Try  hole 140 

Tub(seeladle) 204 

Tungsten 12 

Turgite 37 

Turning  rolls 329 

Tuyere 134 

"     brick 134 

"     cooler 134 

"     cap 135 

"     stock 135 

Tweer  (see  Tuyere) 134 

Twere  (see  tuyere) 134 

Twisted  guide  (see  twisting  guide) 400 

Two  Level  Open  Hearth 209 

Two-high  mill 330 

Two-pass  stove 142 

Two  phase  current 253 

Twyere  (see  tuyere) 134 

Ultimate  analysis 75-76 

strength 304-307 

Uncombined  c  arbon  (see  graphite) 1 27 

Underfill 494 


614 


WORD  INDEX 


Universal  mill   

.  .330-431-433 

Watering  coke 

89-97 

"  plates  

432 

Watt  

245-262 

Up-and-down  takes  

211 

Watt-hour  

262 

Upper  Freeport  coal  bed  

79 

Waynesburg  coal  bed  

79 

"      Kittanning  coal  bed 

79 

Web  holes 

504 

Upset  test 

495 

"     of  a  rail 

440-442-449 

Uranium 

...         11 

Welding  steel 

538 

Valence  

10 

Well  of  open  hearth  
Wellman  furnace 

212 
200 

Vanadium  

12 

Wenstrom  mill  

331 

"       in  case  hardening  

563 

Wet  chemistry 

15 

steel  

595 

Wheel  blank. 

497-504 

Vaporization  heat  of 

59 

"      seat 

512 

"     "in  hardening 

552 

540 

V-connection  
Vermilion  ore  range  
Vibrating  spindle  
Viscosity  of  quenching  liquid  
Volatile  matter  of  coal  
Volt  

225 
46 
334-370 
,552 
76-98 
245-262 

"      metal  
Wicket  
Wind  box  
Window  of  housings  
Wobbler  
Wood 

331 
211 
186 
332 
322 
66-76 

Voltaic  cell  

246 

Work 

243 

Wabbler  (see  wobbler)  

322 

"    effects  of  on  steel  
Working  period  in  open  hearth  .  .  . 

312-535 
223 

Wall  of  blast  furnace  
Walls  of  open  hearth 

136 

210 

Works  annealing  
Wrought  iron.     .  . 

540 
170-171-173 

Wash  heat 

219 

"      oil 

101 

Xanthosiderite  

37 

Washing  open  hearth  furnace 

219 

Xylene  

105 

Waste  heat 

87 

Xylol  ;  

105 

Water,  composition  and  formula.  .  . 
4  '      annealing 

13 
545 

Yield  point  

303 

64 

Y  connections 

255 

551 

Yellow  brass 

331 

"      gas  
hardening  (see  quenching)  .  . 
quenching  
"     seal  
separator  
"      trough... 

71 
551 
551 
73 
149 
139 

Youngs  modulus  

Zee's  (or  Z's)  
Zinc  
"  in  blast  furnace  
Zone  of  fusion  .  .  . 

307 

466 
11 
166 
...167-169 

14  DAY  USE 

:ETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

This  book  is  due  on  the  last  date  stamped  below,  or 
on  the  date  to  which  renewed. 
i  books  are  subject  to  immediate  recall 


. 

~~ 


LD  21A-50m-12,'60 
(B6221slO)476B 


m  General  Library 

University  of  California 

Berkeley 


YB  53337 


425274 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


